Cutaneous Tuberculosis (Skin TB)

Causative Organisms

• Mycobacterium tuberculosis (predominant)
• Occasionally M. bovis and BCG (attenuated M. bovis) can produce skin lesions
• M. tuberculosis is an acid- and alcohol-fast bacillus with a waxy, high-lipid coat that resists degradation after phagocytosis

Classification

Clinical Forms

1. Tuberculous Chancre (Primary Inoculation TB)

• Occurs in non-sensitized (previously unexposed) individuals
• Develops at the site of direct inoculation - a painless, firm, red-brown papule or nodule that may ulcerate ("chancriform" appearance)
• Associated with regional lymphadenopathy (together forming the "primary complex")
• TST is initially negative, becomes positive within 4-8 weeks
• Self-healing but can disseminate
• DDx: sporotrichosis, blastomycosis, syphilis, tularemia, leishmaniasis, cat-scratch disease, atypical mycobacterial infection

2. Tuberculosis Verrucosa Cutis (Prosector's Wart)

• Exogenous inoculation in a previously sensitized person with strong immunity
• The classic "prosector's wart" from autopsy inoculation
• Begins as a small papule becoming hyperkeratotic and wart-like, enlarging by peripheral expansion with or without central clearing
• Surface may fissure with purulent discharge; lesions are almost always solitary
• Commonly on dorsum of fingers/hands (adults) and ankles/buttocks (children)
• TST strongly positive
• Histology: pseudoepitheliomatous hyperplasia, hyperkeratosis, suppurative and granulomatous inflammation; caseation rare; AFB scant
• Culture positive in ~50% of cases

Tuberculosis verrucosa cutis - Andrews' Diseases of the Skin

3. Lupus Vulgaris (Most Common Form)

• Most common form of cutaneous post-primary TB
• Follows inoculation, scrofuloderma scars, or hematogenous/lymphatic spread
• ~50% have evidence of TB elsewhere - full systemic evaluation is mandatory
• Moderately high immunity; TST positive
• Classic appearance: single plaque of grouped red-brown papules with characteristic "apple jelly" color on diascopy (blanching with glass slide pressure)
• Dermoscopy: yellowish-orange patches indicating dermal granulomas
• Lesions are destructive and scarring, especially on the face (nose, cheeks); can result in disfigurement
• Slowly progressive, may develop squamous cell carcinoma in chronic lesions
• DDx: sarcoidosis, discoid lupus erythematosus, rosacea, lymphoma
• Histology: tuberculoid granulomas with or without caseation; AFB are few

4. Scrofuloderma

• Results from direct extension of underlying TB to the skin - usually from infected lymph nodes (cervical most common), bones, or joints
• Presents as firm subcutaneous nodules that soften, break down, and form sinus tracts with collar-stud abscesses and undermined ulcers
• Discharges thin, watery pus
• Heals with irregular, cord-like "bridge" scars
• Most common in children and elderly; cervical/submandibular region favored
• TST positive; AFB may be found; histology shows granulomatous inflammation with caseation

5. Orificial Tuberculosis

• Occurs in patients with advanced systemic TB (lungs, intestinal, urogenital)
• M. tuberculosis auto-inoculates onto mucocutaneous orifices from adjacent infected secretions
• Painful ulcers with undermined edges around mouth, anus, genitalia, or nares
• Indicates severe immunosuppression and poor prognosis
• AFB abundant on smear; TST often negative (anergy)

6. Acute Miliary TB of the Skin

• Due to hematogenous dissemination - a sign of overwhelming TB
• Pinhead-sized bluish-red papules capped by minute vesicles, developing central umbilication and crusting
• Heal leaving white scars with brownish rim
• Primary focus often in lungs

7. Tuberculous Gumma

• Also due to hematogenous spread (mycobacteremia with cutaneous seeding)
• Firm subcutaneous nodule that softens to form a fluctuant swelling
• Overlying skin breaks down to form an undermined ulcer with sinus tract formation
• Extremities more commonly affected than trunk

Tuberculids (Immune Reactions)

• TST/IGRA positive
• AFB usually NOT found in lesions (rapid immune destruction)
• Bilateral and symmetric distribution (hematogenous spread)
• Respond to anti-TB therapy

Papulonecrotic Tuberculid

• Asymptomatic, chronic, recurring crops of papules that undergo central necrosis
• Symmetrically distributed on extensor extremities (elbows, knees), dorsal hands/feet, buttocks, face, glans penis
• Most frequent in children and young adults
• Heals leaving varioliform scars
• Histology: wedge-shaped necrosis, vasculitis, granulomatous inflammation

Lichen Scrofulosorum

• Small, lichenoid follicular papules grouped in discoid clusters
• Usually on trunk; associated with lymph node or bone TB
• Asymptomatic; mainly in children and young adults

Erythema Induratum (Bazin Disease)

• Deep, tender nodules on the posterior calves that ulcerate
• Predominantly in women; associated with cold weather
• Histology: lobular panniculitis with granulomatous inflammation and vasculitis
• M. tuberculosis DNA demonstrable by PCR

Histopathology

• Early lesions: mixed infiltrate of lymphocytes, neutrophils, and plasma cells; AFB abundant
• Established lesions: tuberculoid granulomas - epithelioid macrophages, Langhans giant cells, lymphocytic cuffing, ± central caseation necrosis; AFB difficult to find
• The degree of caseation and AFB load inversely correlates with host immunity

Diagnosis

Treatment

• HRZE = Isoniazid (H) + Rifampicin (R) + Pyrazinamide (Z) + Ethambutol (E)

• HR = Isoniazid + Rifampicin

Special Considerations

• HIV co-infection: ~20-37x higher risk of developing TB; more likely to present atypically; IRIS (immune reconstitution inflammatory syndrome) may worsen skin lesions after starting ART
• TNF inhibitors (biologics like infliximab, adalimumab): major risk factor for reactivation; screen with TST/IGRA before starting
• BCG vaccination: rare complications include local ulceration, lupus vulgaris-like lesions, and disseminated BCG infection (especially in immunocompromised infants)
• Long-standing lupus vulgaris can undergo malignant transformation to squamous cell carcinoma

Neck Swelling - Surgery Viva

APPROACH TO A NECK SWELLING

1. Site - Midline vs. Lateral; which triangle of neck?
2. Size - Dimensions in cm
3. Shape - Ovoid, spherical, irregular
4. Surface - Smooth, nodular
5. Consistency - Soft, firm, hard (stony hard), cystic, fluctuant
6. Skin over swelling - Normal, inflamed, fixed
7. Special tests - Pulsatility, compressibility, transillumination, bruit, movement with swallowing, movement with tongue protrusion (thyroglossal)

CLASSIFICATION BY SITE

MIDLINE NECK SWELLINGS

LATERAL NECK SWELLINGS by Triangle

CLASSIFICATION BY CHARACTER

Acute Swellings

• Cellulitis, Ludwig's angina
• Boil, carbuncle
• Acute lymphadenitis

Chronic Swellings

DIFFERENTIAL DIAGNOSIS (COMPREHENSIVE)

1. Inflammatory / Infective

2. Congenital / Developmental

Thyroglossal Cyst (most important midline swelling)

• Origin: Persistence of thyroglossal duct (thyroid descends from foramen caecum to neck)
• Age: Mainly children, but any age
• Site: Midline, just below the hyoid bone (most common); can be at any level from foramen caecum to isthmus
• Pathognomonic sign: Moves upwards on swallowing AND on tongue protrusion (tethered to base of tongue via the tract)
• Character: Cystic, smooth, non-tender, fluctuant
• Complications: Infection, abscess, fistula, malignancy (papillary carcinoma in 1%)
• Investigation: Ultrasound to confirm (must confirm normal thyroid inferiorly); CT scan
• Treatment: Sistrunk operation - excision of cyst + central portion of hyoid bone + tract up to base of tongue (prevents recurrence)

Branchial Cyst

• Origin: Remnants of second branchial cleft (most common); lined by squamous epithelium
• Age: Young adults (does not manifest in childhood despite being congenital)
• Site: Junction of upper 1/3 and middle 1/3 of sternomastoid, at its anterior border (half in front, half behind SCM); upper/lateral neck
• Character: Soft, ovoid, fluctuant; surface smooth; long axis runs forwards and downwards
• Transillumination: Usually NEGATIVE (content is thick, turbid white fluid containing cholesterol crystals and desquamated epithelial cells)
• Diagnostic test: FNA shows cholesterol crystals - pathognomonic
• Key point: In patients >35 years, always exclude metastatic lymph node (necrotic) before assuming branchial cyst
• Treatment: Complete surgical excision (passes superficial to hypoglossal and glossopharyngeal nerves, deep to posterior belly of digastric; identify spinal accessory nerve)

Branchial Fistula

• Persistent second branchial cleft
• External opening: lower 1/3 of neck, anterior border of SCM
• Internal opening: anterior pillar of fauces, behind the tonsil
• May be unilateral or bilateral

Cystic Hygroma (Lymphangioma)

• Origin: Congenital lymphangioma - abnormal lymphatic development
• Age: Infants and children (usually present at birth or by age 2)
• Site: Root of neck, posterior triangle; may extend to axilla, mediastinum
• Character: Multilocular, brilliantly transilluminates (clear fluid); soft; fluid can be compressed from one locule to another; shows impulse on coughing if mediastinal extension
• Treatment: Sclerotherapy (OK-432, bleomycin) or surgical excision

Dermoid Cyst

• Midline, anywhere; smooth, doughy, non-fluctuant; does NOT transilluminate well; does NOT move with swallowing

Laryngocele

• Air-filled or mucus-filled; arises from laryngeal ventricle
• May be internal (within thyroid cartilage) or external (protrudes through thyrohyoid membrane)
• Increases with Valsalva/coughing; reducible

Cervical Rib

• Posterior triangle, supraclavicular; may cause thoracic outlet syndrome (vascular/neurological symptoms in arm)

3. Neoplastic - Benign

4. Neoplastic - Malignant

Cervical Lymph Node Metastasis (most common malignant neck mass in adults >40)

• Features: Stony hard, irregular surface, fixed to skin or deep structures, painless, rapidly growing
• Majority: Deep to anterior border of SCM
• Search for primary:
  • Above clavicle: Oral cavity (floor of mouth, tongue), tonsil, nasopharynx, larynx, thyroid, external auditory meatus, parotid
  • Left supraclavicular (Virchow's node / Troisier's sign): Infraclavicular primary - stomach, colon, lung, breast, ovary, testis (via thoracic duct)
  • Bilateral supraclavicular: Lymphoma or infraclavicular primary

Primary Lymphoma (Hodgkin's/Non-Hodgkin's)

• Young adults or elderly; rubbery-firm, multiple nodes; systemic "B symptoms" (fever, night sweats, weight loss)
• Hodgkin's: cervical nodes involved in 60-70% of cases

Thyroid Carcinoma

• Moves with swallowing; hard, irregular; may cause hoarseness (recurrent laryngeal nerve invasion), dysphagia, dyspnoea

KEY VIVA QUESTIONS

INVESTIGATIONS FOR NECK SWELLING

Chyle Leak Management

What is Chyle?

• High concentration of triglycerides and chylomicrons
• Lymphocytes (predominantly)
• Fat-soluble vitamins, proteins, immunoglobulins

Anatomy - Why It Matters

• The thoracic duct ascends from the cisterna chyli through the right chest, crosses to the left at T4-5, and enters the neck to empty into the left subclavian vein at or within 1 cm of the junction with the left IJV
• It is more accurately described as a plexus of tributaries - any branch can create a fistula if transected
• Left-sided leaks: 75% - thoracic duct injury
• Right-sided leaks: 25% - right lymphatic duct injury (also important!)

Causes / Etiology

• Neck dissection (radical or modified) - 1-2% incidence
• Esophagectomy - 4.3% incidence
• Lung, mediastinal, or thoracic aortic surgery
• Subclavian vein catheterization
• Blunt/penetrating chest or neck trauma

• Lymphoma (most common non-traumatic cause)
• Lung, esophageal, mediastinal tumours
• Metastatic carcinoma

• Tuberculous lymphadenitis
• Mediastinitis
• Congenital (most common cause of pleural effusion in neonates; associated with Down, Turner, Noonan syndromes)
• Lymphangioleiomyomatosis
• Venous thrombosis (superior vena cava)

Diagnosis

Clinical

• Neck chyle fistula (post-neck dissection): Drain output changes from serosanguinous to milky white after resumption of feeding
• Chylothorax: Dyspnoea, cough, chest discomfort; pleural effusion on CXR

Biochemical (Diagnostic)

• CXR: essential to rule out concurrent chylothorax when neck chyle leak identified
• Lymphangiography/lymphoscintigraphy: Localize the leak site for percutaneous embolization planning

Intraoperative Detection & Management

1. Ask anaesthesiologist to apply positive pressure ventilation - pools milky fluid or reveals discrete lymph vessels
2. Meticulous ligation with non-absorbable sutures (silk)
3. Adjuncts:
   • Operating microscope for identification
   • Fat grafting
   • Surgicel (oxidised cellulose) application
   • Sclerosing agents

Postoperative Management Algorithm

Classification by Output Volume

Conservative Management (Low-Output)

Step 1: Dietary Modification

• Medium-Chain Triglyceride (MCT) diet: MCTs (C6-C12 chain length) are absorbed directly into the portal circulation, bypassing the lymphatic system and reducing chyle flow
• Low-fat or fat-free diet with MCT supplementation
• Note: Long-chain TGs stimulate chyle flow - must be avoided

Step 2: Bowel Rest + Parenteral Nutrition

• NPO (nil per os) + Total Parenteral Nutrition (TPN): Eliminates enteral fat, maximally reduces lymphatic flow
• Most effective at reducing output

Step 3: Pharmacological Reduction of Chyle Flow

Step 4: Wound/Drainage Management

• Closed drainage promotes skin flap adherence
• Pressure dressings over neck (if cervical leak)
• Avoid prolonged continuous drainage (causes chyle loss, malnutrition, immunosuppression)

Interventional / Surgical Management (High-Output or Refractory)

1. Percutaneous Thoracic Duct Embolization (TDE)

• Lymphangiography identifies the site of leak
• Intranodal or pedal lymphangiography → opacifies the thoracic duct
• Percutaneous catheter embolization with coils/glue
• Success rate ~70-80% for post-surgical chylothorax
• Less invasive alternative to surgery; increasingly preferred

2. Surgical Thoracic Duct Ligation

• Approach: Via right chest (thoracotomy or VATS) - the thoracic duct is accessed as it enters the thorax through the diaphragmatic hiatus
• The classic technique ligates all tissue en masse between the aorta, esophagus, spine, and azygos vein (mass ligation)
• VATS (Video-Assisted Thoracoscopic Surgery) is the preferred minimally invasive approach
• Thoracic duct ligation for cervical chyle leak via neck wound re-exploration is also performed

3. Pleurodesis

• Chemical pleurodesis (talc, tetracycline) obliterates pleural space
• Used when definitive surgery is not possible

4. Pleuroperitoneal Shunt

• Refractory cases; relieves symptoms, minimises chyle loss, reduces TPN dependency
• Contraindicated if ascites present
• Risk: shunt occlusion (high fibrinogen in chyle)

5. Indwelling Pleural Catheter (IPC)

• Refractory cases not suitable for surgery
• Allows intermittent drainage at home

Fluid & Nutritional Replacement

• Albumin infusion for hypoalbuminaemia
• TPN to replace caloric and protein losses
• Immunoglobulin supplementation in prolonged leaks (lymphocyte depletion causes immunosuppression)
• Close monitoring of electrolytes

Summary Algorithm

Chyle Leak Diagnosed
        |
        ├── Low output (<500 mL/day)
        |       → NPO + TPN + MCT diet + Octreotide
        |       → Pressure dressing / closed drain
        |       → Wait 2-4 weeks for spontaneous closure
        |
        ├── Moderate (500-1000 mL/day)
        |       → Trial conservative Rx 3-5 days
        |       → If not improving → Intervention
        |
        └── High output (>1000 mL/day)
                → Early intervention
                → Lymphangiography + Percutaneous TDE (first line, if available)
                → If failed → Surgical TD ligation (VATS or open right thoracotomy)
                → Pleurodesis / pleuroperitoneal shunt for refractory cases

Key Viva Points

• Diagnostic fluid TG level: >110 mg/dL (some sources: >100 mg/dL) confirms chyle
• MCT rationale: Absorbed via portal vein, NOT lacteals - bypasses lymphatics
• Octreotide mechanism: Reduces splanchnic blood flow → less mesenteric lymph → less chyle
• Surgical approach for TD ligation: Right chest (not left) - thoracic duct enters from right via aortic hiatus
• Cream via NGT before surgery: Increases chyle flow to identify the leaking duct intraoperatively
• Most common cause of chylothorax in neonate: Congenital (commonest cause of neonatal pleural effusion)
• Most common non-traumatic cause in adults: Lymphoma