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For my dermatology practical exam please give me a proper case description of “neurofibromatoses” taking this as reference patient and also prepare me extensively for the questions that examiner can ask from medium to hard to very hard

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neurofibromatosis type 1 AND dermatology

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Neurofibromatosis type 1 diagnostic criteria management surveillance GeneReviews 2025

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neurofibromatosis type 1 clinical cutaneous neurofibromas café au lait macules plexiform neurofibroma

Imaging modality: Clinical photography of a living patient. Anterior trunk and upper torso view showing numerous cutaneous neurofibromas characteristic of Neurofibromatosis type 1 (NF1, von Recklinghausen disease). Primary subject: skin and subcutaneous tissue involvement with widespread, discrete nodules of varying size on the chest, abdomen, face, and limbs. Lesion morphology includes sessile and pedunculated, dome-shaped nodules that are firm, non-tender, and skin-colored to brown. Two prominent bilateral nipple-areola complex neurofibromas are evident, a finding described as uncommon but highly associated with NF1. The size range observed in this field image is approximately 0.2–2.5 cm. Additional cutaneous manifestations may include cafe-au-lait macules (not clearly visible here) and other soft tissue lesions. The clinical diagnosis is supported by family history and biopsy confirming NF1. Plexiform neurofibromas, when present, are virtually diagnostic of NF1 and warrant ongoing oncologic and neurosurgical surveillance due to potential malignant transformation to malignant peripheral nerve sheath tumors (MPNST). This photograph is valuable for dermatology education and for illustrating characteristic lesion distribution, nomenclature (neurofibroma, plexiform neurofibroma, café-au-lait spots, Lisch nodules), and differential considerations (schwannomatosis, multiple benign cutaneous tumors). Imaging aids in monitoring lesion burden and guiding genetic counseling and clinical management.

Imaging modality: Clinical photography of a living patient. Anterior trunk and upper torso view showing numerous cutaneous neurofibromas characteristic of Neurofibromatosis type 1 (NF1, von Recklinghausen disease). Primary subject: skin and subcutaneous tissue involvement with widespread, discrete nodules of varying size on the chest, abdomen, face, and limbs. Lesion morphology includes sessile and pedunculated, dome-shaped nodules that are firm, non-tender, and skin-colored to brown. Two prominent bilateral nipple-areola complex neurofibromas are evident, a finding described as uncommon but highly associated with NF1. The size range observed in this field image is approximately 0.2–2.5 cm. Additional cutaneous manifestations may include cafe-au-lait macules (not clearly visible here) and other soft tissue lesions. The clinical diagnosis is supported by family history and biopsy confirming NF1. Plexiform neurofibromas, when present, are virtually diagnostic of NF1 and warrant ongoing oncologic and neurosurgical surveillance due to potential malignant transformation to malignant peripheral nerve sheath tumors (MPNST). This photograph is valuable for dermatology education and for illustrating characteristic lesion distribution, nomenclature (neurofibroma, plexiform neurofibroma, café-au-lait spots, Lisch nodules), and differential considerations (schwannomatosis, multiple benign cutaneous tumors). Imaging aids in monitoring lesion burden and guiding genetic counseling and clinical management.

Clinical photographs demonstrating the cutaneous manifestations of Neurofibromatosis Type 1 (NF1). Figure A presents a frontal view of a male patient with a massive plexiform neurofibroma on the left side of the face. The soft tissue tumor causes severe facial asymmetry and disfigurement, characterized by overhanging skin folds, complete eyelid ptosis, and inferior displacement of the left eye, involving the temporal, orbital, cheek, nose, and chin regions. Figure B provides a detailed view of the patient's trunk and arms, illustrating characteristic dermatological findings. These include multiple pedunculated and sessile neurofibromas (indicated by straight arrows), which appear as skin-colored, raised nodules, and several café-au-lait macules (indicated by curved arrows), which are flat, hyperpigmented, light-brown patches with smooth borders. This composite image serves as a visual reference for the range of severity in NF1, from common cutaneous lesions to debilitating plexiform neurofibromas.

Clinical photographs demonstrating the cutaneous manifestations of Neurofibromatosis Type 1 (NF1). Figure A presents a frontal view of a male patient with a massive plexiform neurofibroma on the left side of the face. The soft tissue tumor causes severe facial asymmetry and disfigurement, characterized by overhanging skin folds, complete eyelid ptosis, and inferior displacement of the left eye, involving the temporal, orbital, cheek, nose, and chin regions. Figure B provides a detailed view of the patient's trunk and arms, illustrating characteristic dermatological findings. These include multiple pedunculated and sessile neurofibromas (indicated by straight arrows), which appear as skin-colored, raised nodules, and several café-au-lait macules (indicated by curved arrows), which are flat, hyperpigmented, light-brown patches with smooth borders. This composite image serves as a visual reference for the range of severity in NF1, from common cutaneous lesions to debilitating plexiform neurofibromas.

Clinical photograph of a patient's torso displaying characteristic cutaneous manifestations of Neurofibromatosis type 1 (NF1). The right breast exhibits severe deformity and soft tissue overgrowth caused by an extensive plexiform neurofibroma. The lesion involves the outer quadrants, extending to the nipple-areolar complex and toward the homolateral axilla, resulting in a pendulous, bag-like enlargement with a reddish-purple hue and a striated, thickened skin texture (pachydermatous changes). In contrast, the left breast appears normal in morphology. Adjacent to the left breast on the upper chest is a large, irregular depigmented patch consistent with vitiligo. Additionally, the trunk displays multiple café-au-lait macules—well-circumscribed, light-brown pigmented spots—and smaller, scattered cutaneous neurofibromas. The image illustrates the significant aesthetic and structural disfigurement associated with plexiform neurofibromas, which are pathognomonic for NF1 and involve diffuse nerve sheath thickening that can infiltrate surrounding dermal and subcutaneous layers.

Clinical photograph of a patient's torso displaying characteristic cutaneous manifestations of Neurofibromatosis type 1 (NF1). The right breast exhibits severe deformity and soft tissue overgrowth caused by an extensive plexiform neurofibroma. The lesion involves the outer quadrants, extending to the nipple-areolar complex and toward the homolateral axilla, resulting in a pendulous, bag-like enlargement with a reddish-purple hue and a striated, thickened skin texture (pachydermatous changes). In contrast, the left breast appears normal in morphology. Adjacent to the left breast on the upper chest is a large, irregular depigmented patch consistent with vitiligo. Additionally, the trunk displays multiple café-au-lait macules—well-circumscribed, light-brown pigmented spots—and smaller, scattered cutaneous neurofibromas. The image illustrates the significant aesthetic and structural disfigurement associated with plexiform neurofibromas, which are pathognomonic for NF1 and involve diffuse nerve sheath thickening that can infiltrate surrounding dermal and subcutaneous layers.

Clinical photograph of a 26-year-old male showing cutaneous manifestations of Neurofibromatosis type 1 (Von Recklinghausen disease). The most striking feature is a large, firm, and irregular plexiform neurofibroma located in the left latero-cervical and supraclavicular region, measuring approximately 10 cm and significantly distorting the neck contour. The patient's torso exhibits classic stigmata of the condition, including multiple hyperpigmented macules (café-au-lait spots) and small, disseminated cutaneous neurofibromas. A surgical dressing is visible on the upper right thoracic wall, corresponding to the site of a synovial sarcoma resection. This image illustrates the multi-system involvement of NF1 and the increased risk for associated malignancies, such as soft tissue sarcomas. The photograph is an educational resource for medical students and clinicians to recognize both the benign neurofibromas and the complex clinical presentation of syndromic oncology patients.

Clinical photograph of a 26-year-old male showing cutaneous manifestations of Neurofibromatosis type 1 (Von Recklinghausen disease). The most striking feature is a large, firm, and irregular plexiform neurofibroma located in the left latero-cervical and supraclavicular region, measuring approximately 10 cm and significantly distorting the neck contour. The patient's torso exhibits classic stigmata of the condition, including multiple hyperpigmented macules (café-au-lait spots) and small, disseminated cutaneous neurofibromas. A surgical dressing is visible on the upper right thoracic wall, corresponding to the site of a synovial sarcoma resection. This image illustrates the multi-system involvement of NF1 and the increased risk for associated malignancies, such as soft tissue sarcomas. The photograph is an educational resource for medical students and clinicians to recognize both the benign neurofibromas and the complex clinical presentation of syndromic oncology patients.

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https://pmc.ncbi.nlm.nih.gov/articles/PMC8354850

The photograph shows several skin-colored, smooth, soft-looking papules/nodules on the forehead and left malar area, clinically compatible with cutaneous neurofibromas in the appropriate context. A photograph alone cannot confirm NF1: examine the entire skin, axillae/groins, eyes, skeleton, neurologic status, and family history.
Asking for Preferences

Which viva-preparation module should I expand first after the case presentation?

The photograph shows several skin-colored, smooth, soft-looking papules/nodules on the forehead and left malar area, clinically compatible with cutaneous neurofibromas in the appropriate context. A photograph alone cannot confirm NF1: examine the entire skin, axillae/groins, eyes, skeleton, neurologic status, and family history.## Provisional practical case presentation
This patient has multiple skin-colored papules and nodules over the face, including the forehead and left malar region. The lesions appear smooth-surfaced, discrete, dome-shaped, and non-ulcerated. In the clinical context, these are suggestive of cutaneous neurofibromas.
The likely diagnosis is Neurofibromatosis type 1 (NF1), also called von Recklinghausen disease, provided the patient meets diagnostic criteria on complete examination. A photo alone cannot establish NF1, because café-au-lait macules, axillary/inguinal freckling, ocular signs, family history, and systemic examination must be assessed.

Spoken long-case format

“This is a middle-aged female patient with multiple asymptomatic, gradually progressive, skin-colored papules and nodules over the face. The lesions are discrete, smooth-surfaced, skin-colored, soft-looking, and non-tender, without ulceration or discharge. The facial lesions are clinically suggestive of cutaneous neurofibromas.
I would examine the whole skin for café-au-lait macules, axillary and inguinal freckling, additional cutaneous or subcutaneous neurofibromas, and any plexiform neurofibroma. I would perform ophthalmic examination for Lisch nodules and optic pathway involvement, assess blood pressure and cardiovascular status, examine the spine and long bones for skeletal deformity, and assess neurologic and developmental status.
I would also ask for family history of similar lesions, visual complaints, headache, seizures, limb weakness, pain or rapid enlargement of any swelling, and learning difficulties in childhood.
My provisional diagnosis is Neurofibromatosis type 1 with multiple cutaneous neurofibromas. The important concern is to identify a plexiform neurofibroma or a malignant peripheral nerve sheath tumour.”

Points to demonstrate on examining this patient

  • Describe lesion site, number, morphology, surface, color, consistency, and symptoms.
  • Palpate lesions. Cutaneous neurofibromas may be soft and compressible. The classic buttonhole sign is invagination of a soft neurofibroma into the skin on pressure.
  • Search for:
    • Café-au-lait macules: uniformly light-to-dark brown, well-defined, usually smooth-bordered ("coast of California") macules.
    • Axillary or inguinal freckling: Crowe sign.
    • Plexiform neurofibroma: diffuse, ill-defined, tortuous thickening along nerves, often described as a "bag of worms."
    • Skeletal signs: scoliosis, tibial anterolateral bowing/pseudarthrosis, sphenoid wing dysplasia.
    • Ophthalmic signs: Lisch nodules and choroidal abnormalities.
    • Hypertension and symptoms suggesting pheochromocytoma.
    • Neurological deficits or signs of intracranial lesion.

The key diagnostic criteria you must know

For a person without an affected parent, NF1 requires two or more of the following revised criteria:
  1. Six or more café-au-lait macules
    • 5 mm in greatest diameter before puberty
    • 15 mm after puberty
  2. Axillary or inguinal freckling
  3. Two or more neurofibromas of any type, or one plexiform neurofibroma
  4. Optic pathway glioma
  5. Two or more Lisch nodules on slit-lamp examination, or two or more choroidal abnormalities on OCT/near-infrared imaging
  6. A characteristic bony lesion:
    • Sphenoid dysplasia
    • Anterolateral bowing of tibia
    • Pseudarthrosis of a long bone
  7. A heterozygous pathogenic NF1 variant in normal tissue.
If a parent has NF1, one diagnostic feature in the child is sufficient. The revised international criteria are detailed in this consensus statement.

Examiner-viva roadmap

To prepare extensively, focus on these modules:
  1. Clinical case presentation and morphology
    • How to describe neurofibromas correctly
    • Buttonhole sign
    • Cutaneous versus subcutaneous versus plexiform neurofibroma
  2. NF1 diagnosis and differentials
    • Revised diagnostic criteria
    • Legius syndrome
    • Segmental or mosaic NF1
    • NF2-related schwannomatosis and other schwannomatoses
    • Café-au-lait macules in other disorders
  3. Genetics and pathogenesis
    • NF1 gene, chromosome 17q11.2
    • Neurofibromin and RAS-MAPK pathway
    • Autosomal-dominant inheritance, variable expressivity, de novo disease
  4. Systemic manifestations and complications
    • Optic pathway glioma
    • Plexiform neurofibroma
    • MPNST
    • Skeletal disease, learning issues, vasculopathy, pheochromocytoma, breast cancer risk
  5. Investigations, counselling, surveillance, and treatment
    • When MRI or PET imaging is appropriate
    • Red flags for MPNST
    • Surgical and medical management
    • MEK inhibitors, particularly selumetinib for selected inoperable symptomatic plexiform neurofibromas
    • Genetic counselling and family screening
High-yield safety statement for the exam: rapid increase in size, persistent or nocturnal pain, new hardness in a previously soft lesion, and new neurologic deficit in a plexiform neurofibroma suggest possible malignant transformation to MPNST and require urgent evaluation. This is consistent with ERN GENTURIS surveillance guidance.
Which one should I take next in full viva format: diagnostic criteria, differentials, genetics/pathogenesis, complications/surveillance, or treatment with medium-to-very-hard examiner questions and model answers?

Describe the location of the lesion near eyebrow

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facial anatomical terminology forehead supraorbital eyebrow region dermatology lesion description

The lesion is located on the left supraorbital forehead, just superolateral to the left eyebrow, near the lateral end of the eyebrow.
For practical description, say:
“A solitary, skin-colored, dome-shaped nodule is present over the left supraorbital region of the forehead, approximately 1-2 cm above the lateral aspect of the left eyebrow.”
Avoid calling it an eyelid lesion, as it is above the eyebrow on the forehead, not on the eyelid.

One near the eye at right side

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The lesion near the eye is over the left infraorbital/malar region, just inferolateral to the left lower eyelid and lateral to the side of the nose.
Say:
“Multiple small skin-colored papules are present over the left infraorbital and malar region, located just below and lateral to the left eye.”
Note: this is the right side of the photograph, but the patient’s left side.

Prepare me for questions examiner can ask on this topic from moderate to hard to very hard questions with answers

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neurofibromatosis type 1 AND management

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2025 neurofibromatosis type 1 clinical management surveillance selumetinib guideline

Neurofibromatosis type 1: examiner-viva map

This topic can be tested in five areas:
  1. Recognition and clinical description
    • Morphology of cutaneous neurofibromas
    • Buttonhole sign
    • Café-au-lait macules, Crowe sign, plexiform neurofibroma
  2. Diagnosis and differentials
    • Revised NF1 diagnostic criteria
    • Legius syndrome, segmental/mosaic NF1
    • NF2-related schwannomatosis and other causes of café-au-lait macules
  3. Genetics and pathology
    • NF1 gene, neurofibromin, RAS-MAPK pathway
    • Autosomal-dominant inheritance, penetrance, variable expression
    • Histopathology and immunohistochemistry
  4. Complications and surveillance
    • Optic pathway glioma, skeletal disease, learning problems, hypertension
    • Plexiform neurofibroma and MPNST
    • Pheochromocytoma/paraganglioma, GIST, breast cancer risk
  5. Management
    • Counselling and family screening
    • Indications for imaging and biopsy
    • Surgery and selumetinib for selected symptomatic inoperable plexiform neurofibromas
High-level exam takeaway: This photo is suggestive of facial cutaneous neurofibromas, but NF1 is a clinicogenetic diagnosis requiring full skin examination and assessment for diagnostic criteria and systemic complications. A painful, rapidly growing, hardening neurofibroma or new neurological deficit must raise concern for malignant peripheral nerve sheath tumour.
Select the first module you want in full moderate-to-very-hard Q&A format:
  • A. Diagnosis and differentials
  • B. Genetics, pathogenesis and histopathology
  • C. Complications and surveillance
  • D. Management and treatment
  • E. Full mixed mock viva

Just give me all the questions you gave earlier for other spotters

Neurofibromatosis type 1 (NF1): Spotter Viva Questions with Answers

Moderate-level questions

1. What is your diagnosis?

Neurofibromatosis type 1 (NF1), also called von Recklinghausen disease, with multiple cutaneous neurofibromas.

2. What are the lesions seen in this patient?

They are cutaneous neurofibromas: soft, skin-colored to slightly hyperpigmented, sessile or pedunculated papules/nodules.

3. Describe a cutaneous neurofibroma.

It is a benign peripheral nerve-sheath tumour presenting as a soft, skin-colored, dome-shaped or pedunculated papule/nodule. It may be solitary or multiple and commonly appears during adolescence or adulthood.

4. What is the buttonhole sign?

On pressure, a soft cutaneous neurofibroma can be invaginated into the skin, like passing through a buttonhole. It is a useful clinical sign of neurofibroma.

5. What are the main types of neurofibroma?

  1. Localized cutaneous neurofibroma
  2. Subcutaneous neurofibroma
  3. Diffuse neurofibroma
  4. Plexiform neurofibroma

6. What is a plexiform neurofibroma?

A plexiform neurofibroma is a diffuse, often congenital tumour involving multiple fascicles of a nerve and its branches. It feels like a “bag of worms”, can cause major disfigurement and functional impairment, and is strongly associated with NF1.

7. What is the importance of plexiform neurofibroma?

It is highly suggestive of NF1 and has a risk of progression to atypical neurofibromatous neoplasm of uncertain biologic potential (ANNUBP) and malignant peripheral nerve sheath tumour (MPNST).

8. What are café-au-lait macules?

They are flat, uniformly light-brown to dark-brown hyperpigmented macules with smooth, well-defined borders. In NF1, they classically have a smooth “coast of California” border.

9. How many café-au-lait macules are significant in NF1?

Six or more:
  • More than 5 mm in greatest diameter in a prepubertal child
  • More than 15 mm in a postpubertal person

10. What is Crowe sign?

Axillary or inguinal freckling in NF1. It usually develops in early childhood and is diagnostically important.

11. What are Lisch nodules?

They are benign, melanocytic hamartomas of the iris. They are best detected by slit-lamp examination and do not typically affect vision.

12. Are Lisch nodules present at birth?

Usually no. Their frequency increases with age, so their absence in a young child does not rule out NF1.

13. What should you ask in history?

Ask about:
  • Age at onset and progression of lesions
  • Family history of similar lesions, pigmentary lesions, or known NF1
  • Pain, rapid growth, hardening, or neurological symptoms in any tumour
  • Visual symptoms, proptosis, squint, headache, seizures
  • Learning difficulty, poor school performance, ADHD
  • Bone pain, limb deformity, scoliosis
  • Hypertension symptoms, palpitations, sweating, headache
  • Menstrual/sexual precocity in children, suggesting optic/hypothalamic involvement

14. What should you examine apart from the visible lesions?

  • Full skin examination for café-au-lait macules and neurofibromas
  • Axillae and groins for freckling
  • Eyes for Lisch nodules and visual impairment
  • Spine for scoliosis
  • Long bones for tibial bowing/pseudarthrosis
  • Blood pressure
  • Neurological examination
  • Development, cognition, and school performance in children
  • Breast examination and appropriate screening discussion in adult women

Diagnostic criteria

15. State the revised diagnostic criteria for NF1.

In a person without an affected parent, diagnosis requires two or more of:
  1. Six or more café-au-lait macules of appropriate size
  2. Axillary or inguinal freckling
  3. Two or more neurofibromas of any type, or one plexiform neurofibroma
  4. Optic pathway glioma
  5. Two or more Lisch nodules, or two or more choroidal abnormalities on appropriate imaging
  6. Distinctive osseous lesion: sphenoid dysplasia, anterolateral tibial bowing, or pseudarthrosis of a long bone
  7. A heterozygous pathogenic NF1 variant in normal tissue
If one parent meets NF1 diagnostic criteria, a child requires one of these features.

16. Is genetic testing mandatory for diagnosis?

No. NF1 is frequently diagnosed clinically. Genetic testing is useful when the phenotype is incomplete, in young children, in suspected mosaic disease, or for reproductive counselling.

17. Which gene is mutated in NF1?

The NF1 gene on chromosome 17q11.2.

18. What does the NF1 gene encode?

It encodes neurofibromin, a tumour-suppressor protein.

19. Explain the role of neurofibromin.

Neurofibromin normally acts as a RAS GTPase-activating protein, converting active RAS-GTP to inactive RAS-GDP. Loss of neurofibromin leads to excessive RAS-MAPK pathway signalling and predisposes to tumour development.

20. What is the inheritance pattern?

It is autosomal dominant with near-complete penetrance but marked variable expressivity.

21. What is the recurrence risk for offspring of an affected person?

Each child has a 50% chance of inheriting the pathogenic NF1 variant.

22. How often is NF1 a new mutation?

Approximately half of cases are due to a de novo pathogenic variant.

23. Can severity be predicted from the severity in the parent?

No. Even within the same family, clinical expression can vary greatly.

Differential diagnosis

24. What is the differential diagnosis of multiple skin-colored papules/nodules on the face?

  • Multiple cutaneous neurofibromas in NF1
  • Multiple schwannomas
  • Multiple trichoepitheliomas
  • Fibrofolliculomas, such as in Birt-Hogg-Dubé syndrome
  • Angiofibromas of tuberous sclerosis
  • Syringomas
  • Skin tags, if pedunculated
  • Leiomyomas, usually firmer and may be painful

25. What is the differential diagnosis of multiple café-au-lait macules?

  • NF1
  • Legius syndrome
  • McCune-Albright syndrome
  • Constitutional mismatch repair deficiency syndrome
  • Noonan syndrome with multiple lentigines
  • Watson syndrome
  • Isolated familial café-au-lait macules

26. Differentiate NF1 from Legius syndrome.

FeatureNF1Legius syndrome
GeneNF1SPRED1
Café-au-lait maculesPresentPresent
Axillary frecklingPresentMay occur
NeurofibromasPresentAbsent
Lisch nodulesMay occurAbsent
Optic pathway gliomaMay occurAbsent
Major tumour predispositionPresentNot characteristic
Key answer: Legius syndrome may mimic early NF1 due to café-au-lait macules and freckling, but it lacks neurofibromas, Lisch nodules, optic glioma, and characteristic osseous lesions.

27. What is segmental or mosaic NF1?

It is NF1 caused by a post-zygotic pathogenic variant, producing features restricted to one body segment or region. The distribution often follows a unilateral or segmental pattern and may not cross the midline.

28. Can a patient with segmental NF1 transmit generalized NF1 to their children?

Yes. If gonadal cells carry the pathogenic variant, there is a risk of transmission. This is termed gonadal mosaicism.

29. Differentiate NF1 from NF2-related schwannomatosis.

NF1 is characterized by café-au-lait macules, axillary freckling, cutaneous and plexiform neurofibromas, Lisch nodules, optic pathway gliomas, and skeletal lesions.
NF2-related schwannomatosis is characterized mainly by bilateral vestibular schwannomas, other cranial/spinal schwannomas, meningiomas, ependymomas, and juvenile cataracts. Cutaneous findings are much less prominent.

Hard questions: complications

30. Name the important complications of NF1.

  • Plexiform neurofibroma
  • MPNST
  • Optic pathway glioma
  • Other low-grade gliomas
  • Learning disability, ADHD, developmental delay
  • Skeletal abnormalities: scoliosis, tibial pseudarthrosis, sphenoid wing dysplasia
  • Hypertension due to renal artery stenosis, coarctation, or pheochromocytoma
  • Pheochromocytoma/paraganglioma
  • Gastrointestinal stromal tumour
  • Glomus tumours
  • Juvenile myelomonocytic leukaemia, especially in children
  • Increased breast cancer risk in women
  • Cerebrovascular abnormalities, including moyamoya vasculopathy

31. Which tumour is most feared in NF1?

Malignant peripheral nerve sheath tumour, or MPNST.

32. What features suggest malignant transformation of a plexiform neurofibroma?

Red flags are:
  • Rapid increase in size or change in growth rate
  • New, persistent, severe, or nocturnal pain
  • New hard area within a previously soft lesion
  • New motor weakness, sensory loss, or neuropathic symptoms
  • Bladder/bowel dysfunction, dysphagia, or respiratory compromise depending on location

33. What is the work-up if you suspect MPNST?

  • Urgent assessment by an NF1/sarcoma multidisciplinary team
  • Regional MRI to define the lesion
  • FDG-PET/CT or FDG-PET/MRI to identify metabolically active suspicious areas
  • Image-guided core biopsy targeting the suspicious region, planned with the sarcoma team
  • Staging imaging if malignancy is confirmed

34. Why should an incisional biopsy not be done casually in suspected MPNST?

Poorly planned biopsy may contaminate tissue planes and compromise definitive limb-sparing or oncologic surgery. Biopsy should be planned by the specialist sarcoma team.

35. What is ANNUBP?

Atypical neurofibromatous neoplasm of uncertain biologic potential is an intermediate lesion between benign plexiform neurofibroma and MPNST. It shows atypical features but does not fulfill criteria for malignancy.

36. What is an optic pathway glioma?

A usually low-grade glioma affecting the optic nerve, optic chiasm, optic tract, or related pathways. It is associated with NF1, often arises in childhood, and may be asymptomatic.

37. Does every child with NF1 need screening MRI of brain and orbits?

No. Routine screening MRI in asymptomatic children is not generally recommended. Regular clinical and ophthalmological assessment is preferred. MRI is indicated for visual symptoms, concerning examination findings, or when adequate ophthalmic assessment cannot be performed.

38. Which child with NF1 is at risk of precocious puberty?

A child with an optic pathway glioma involving or affecting the chiasm/hypothalamic region.

39. What are the skeletal manifestations of NF1?

  • Scoliosis, both dystrophic and non-dystrophic
  • Anterolateral bowing of tibia
  • Tibial pseudarthrosis
  • Sphenoid wing dysplasia
  • Vertebral scalloping
  • Short stature and reduced bone mineral density in some patients

40. Why should blood pressure be checked at every visit?

NF1 can be associated with hypertension due to:
  • Essential hypertension
  • Renal artery stenosis
  • Coarctation of the aorta
  • Pheochromocytoma or paraganglioma
  • Other NF1-associated vasculopathies

41. When should you suspect pheochromocytoma in NF1?

In an NF1 patient with hypertension, episodic headache, palpitations, sweating, tremor, pallor, or an adrenal mass. Test plasma free metanephrines or urinary fractionated metanephrines.

42. What malignancy screening issue is important in adult women with NF1?

Women with NF1 have increased risk of early breast cancer. They require early individualized breast-cancer surveillance, commonly including annual breast MRI from around age 30 according to local guideline practice.

Histopathology and very hard questions

43. What is the histopathology of a neurofibroma?

A non-encapsulated dermal or subcutaneous proliferation of spindle cells with wavy, serpentine nuclei in a loose myxoid collagenous stroma. It contains Schwann cells, fibroblasts, mast cells, and perineurial-like cells, often with entrapped axons.

44. Why is a neurofibroma usually non-encapsulated?

Because it infiltrates the parent nerve and surrounding tissue rather than being a sharply circumscribed tumour.

45. How is neurofibroma differentiated from schwannoma histologically?

NeurofibromaSchwannoma
Usually non-encapsulatedUsually encapsulated
Entraps axonsTypically displaces axons outside the tumour
Mixed cell populationPredominantly Schwann cells
Wavy spindle cells in myxoid backgroundAntoni A and Antoni B areas, Verocay bodies
Can be plexiform in NF1Plexiform schwannoma is distinct and not typical of NF1

46. Which immunohistochemical markers are useful?

  • S100 and SOX10: positive in Schwann-cell component, often patchy in neurofibroma
  • CD34: highlights fibroblastic component
  • Neurofilament protein: highlights entrapped axons
  • EMA: may highlight perineurial cells
  • Ki-67: helps evaluate proliferative activity in atypical or malignant lesions
  • H3K27me3 loss can support MPNST in the appropriate pathological context

47. Why do neurofibromas develop in NF1 although every cell carries one altered NF1 allele?

Tumour formation generally follows a two-hit mechanism: a germline pathogenic NF1 variant is followed by somatic loss of the remaining functional allele in susceptible cells, especially Schwann-cell lineage cells.

48. What is the role of mast cells in neurofibroma formation?

NF1-deficient Schwann cells influence the tumour microenvironment, recruiting mast cells and other stromal cells. These cells support tumour development through growth factors, cytokines, matrix remodelling, and angiogenic signalling.

49. Why are cutaneous neurofibromas common in adolescence and pregnancy?

Hormonal influences may contribute to growth of neurofibromas. Lesion number and size can increase during puberty and pregnancy, although the degree of change varies.

50. Are cutaneous neurofibromas premalignant?

No. Cutaneous neurofibromas are benign and generally do not transform into MPNST. The important precursor lesion for MPNST is usually a deep plexiform neurofibroma.

Management questions

51. How do you manage a patient with NF1?

Management is lifelong, multidisciplinary, and individualized:
  • Clinical diagnosis and genetic counselling
  • Education about red-flag symptoms
  • Annual or periodic clinical review depending on age and complications
  • Full skin, neurologic, skeletal, visual, and blood-pressure assessment
  • Ophthalmology surveillance in children
  • Developmental, behavioural, and educational support
  • Targeted imaging only when clinically indicated
  • Referral to relevant specialties for tumours or complications

52. How are asymptomatic cutaneous neurofibromas managed?

Reassurance and observation are appropriate. Treatment is indicated for symptoms such as pain, pruritus, bleeding, recurrent trauma, functional impairment, or significant cosmetic distress.

53. What treatment options exist for cutaneous neurofibromas?

  • Surgical excision
  • Shave excision
  • Electrosurgery/electrodessication
  • Laser treatment in selected cases
  • Radiofrequency ablation in selected settings
The method depends on lesion number, size, site, scarring risk, and local expertise.

54. How is a plexiform neurofibroma managed?

  • Assess by an NF1 multidisciplinary team
  • MRI for anatomy, extent, and serial follow-up when indicated
  • Surgery if complete resection is feasible and morbidity is acceptable
  • Observe stable asymptomatic lesions
  • Consider a MEK inhibitor, such as selumetinib, for selected symptomatic, inoperable plexiform neurofibromas, especially in paediatric patients where locally approved

55. What is selumetinib and how does it work?

Selumetinib is an oral MEK1/2 inhibitor. It reduces signalling through the RAS-RAF-MEK-ERK pathway, which is overactive after loss of neurofibromin in NF1.

56. What adverse effects should be monitored with selumetinib?

  • Acneiform or other rash
  • Diarrhoea
  • Nausea/vomiting
  • Elevated creatine kinase
  • Paronychia
  • Ocular toxicity, including retinal changes
  • Reduced left ventricular ejection fraction
Monitoring includes clinical review, echocardiography, ophthalmological assessment, and relevant laboratory tests. Evidence for selumetinib in inoperable plexiform neurofibromas is supported by a 2024 systematic review and meta-analysis.

57. What counselling should be provided?

  • NF1 is autosomal dominant
  • Each child has a 50% transmission risk if the parent has a germline pathogenic variant
  • Severity cannot be reliably predicted in offspring
  • Offer genetic counselling before conception
  • Discuss testing options according to local laws and services
  • Counsel on warning symptoms of MPNST and need for lifelong follow-up

Rapid-fire very hard viva

58. Why are café-au-lait macules not specific for NF1?

They occur in multiple genetic and non-genetic conditions. Their diagnostic significance depends on number, size, distribution, associated signs, and family history.

59. Why are the borders of NF1 café-au-lait macules described as coast of California?

They are typically smooth and regular. In contrast, McCune-Albright syndrome tends to have irregular, jagged “coast of Maine” borders, often respecting the midline.

60. What is the difference between generalized NF1 and mosaic NF1 genetically?

Generalized NF1 results from a pathogenic variant present in the germline, so it is in essentially all cells. Mosaic NF1 results from a post-zygotic mutation and is present only in a subset of cells.

61. Why can a blood NF1 genetic test be negative in mosaic NF1?

The pathogenic variant may be absent or present at a very low level in circulating blood leukocytes. Testing affected tissue may be required.

62. Is NF1 the same as “elephant man disease”?

No. This is a common misconception. Joseph Merrick, historically called the Elephant Man, is now thought to have had Proteus syndrome, not NF1.

63. Which tumour is more associated with NF1: schwannoma or neurofibroma?

Neurofibroma, especially plexiform neurofibroma. Multiple schwannomas are more characteristic of NF2-related schwannomatosis or other schwannomatoses.

64. What is the significance of a solitary neurofibroma?

A solitary localized neurofibroma is common and usually sporadic. It does not by itself imply NF1.

65. Is every patient with NF1 equally likely to develop MPNST?

No. Risk is higher in patients with extensive internal tumour burden, plexiform neurofibromas, atypical neurofibromas/ANNUBP, previous radiotherapy, and certain genotype-phenotype associations.

66. Why should radiotherapy be avoided where possible in NF1?

People with NF1 have a predisposition to tumours and may be at increased risk of radiation-associated secondary malignancies, including MPNST. Decisions require specialist multidisciplinary input.

67. What is the most appropriate single sentence to end your spotter presentation?

“This patient has multiple facial cutaneous neurofibromas, and my provisional diagnosis is neurofibromatosis type 1; I would complete the diagnostic assessment by looking for pigmentary, ocular, skeletal, neurological, and familial features, while specifically excluding a plexiform neurofibroma or features of malignant peripheral nerve sheath tumour.”
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