Briefly explain this specimen for final year mbbs student surgery practical examination based on muhs pattern reference srb manual of surgery
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Based on my analysis of the specimen images and library resources, here is a structured answer for the MUHS Final Year MBBS Surgery Practical examination, in the SRB Manual pattern:
Specimen: Retroperitoneal Liposarcoma (Well-Differentiated)
Identification of the Specimen
This is a formalin-preserved gross surgical specimen showing a large, lobulated, yellowish-white fatty mass with an encapsulated, smooth dark-brownish ovoid structure (displaced/enveloped kidney or adrenal gland) embedded within it. The mass has an irregular, nodular surface with a greasy, adipose-like cut appearance.
Diagnosis: Retroperitoneal Liposarcoma (most likely Well-Differentiated type)
Description of the Specimen
| Feature | Finding |
|---|---|
| Size | Large (fills the container) |
| Shape | Lobulated, multilobular |
| Colour | Yellow-white (lipomatous) with darker brownish zones |
| Surface | Irregular, nodular, lobulated |
| Consistency | Fatty/greasy (adipocytic) |
| Associated structure | Dark ovoid structure (likely displaced kidney surrounded by perinephric fat) |
| Capsule | Ill-defined, no true capsule |
| Cut section | Yellowish lobules with fibrous septa |
What is Liposarcoma?
A liposarcoma is a malignant mesenchymal tumour with adipocytic differentiation. It is the most common retroperitoneal sarcoma and the most common soft tissue sarcoma in adults (5th–6th decade of life).
Classification (SRB / WHO)
- Well-differentiated liposarcoma (most common) — indolent, excellent prognosis if completely excised; amplification of MDM2 (12q13–q15)
- Myxoid liposarcoma — intermediate malignancy; (12;16) translocation
- Pleomorphic liposarcoma — aggressive, frequent metastasis; complex karyotype
- Dedifferentiated liposarcoma — arises within well-differentiated tumour; aggressive
Retroperitoneal Site — Key Points
- Most common location for liposarcoma: retroperitoneum (60%)
- Presents late due to silent space → large size at diagnosis
- Can displace/encase adjacent structures: kidney, ureter, aorta, IVC
- The dark ovoid structure seen in this specimen = displaced kidney surrounded by tumour (classic gross feature)
Clinical Presentation
- Large, painless abdominal mass (most common)
- Vague abdominal discomfort, backache
- Weight loss, anorexia (late features)
- Urinary symptoms if kidney/ureter involved
- Rarely: lower limb oedema (IVC compression)
Investigations
- USG abdomen: Large retroperitoneal mass, echogenic (fat density)
- CECT abdomen (investigation of choice): Heterogeneous retroperitoneal mass with fat attenuation (−20 to −100 HU); may show calcification, necrosis, fibrous septa
- MRI: Superior soft tissue characterisation
- Biopsy (CT-guided Trucut): For histological confirmation before surgery
- Chest CT: Staging — rule out pulmonary metastasis
Treatment
Surgery (Mainstay)
- Wide local excision / Radical resection with en-bloc removal of adjacent structures (kidney, adrenal, bowel segment) is the treatment of choice
- Aim: R0 resection (clear margins) — most important prognostic factor
- Retroperitoneal liposarcomas frequently recur even after complete excision
Adjuvant Therapy
- Radiotherapy: Used post-operatively for high-grade tumours or positive margins (60–70 Gy)
- Chemotherapy (doxorubicin + ifosfamide): for high-grade/metastatic disease; response rates modest (~25%)
Prognosis
| Subtype | Prognosis |
|---|---|
| Well-differentiated | Excellent (rarely metastasizes) |
| Myxoid | Intermediate |
| Pleomorphic / Dedifferentiated | Poor (high recurrence + metastasis) |
- Retroperitoneal liposarcomas have higher recurrence rates (60–80%) than extremity lesions due to difficulty achieving negative margins
- 5-year survival: ~50–70% (well-differentiated) → <20% (pleomorphic)
Viva Questions Likely Asked in MUHS Exam
Q: What is the most common soft tissue sarcoma in adults?
A: Liposarcoma
Q: What is the investigation of choice?
A: CECT abdomen (shows fat attenuation, hallmark of liposarcoma)
Q: What is the most important prognostic factor?
A: Completeness of surgical resection (R0 margins)
Q: What gene is amplified in well-differentiated liposarcoma?
A: MDM2 (chromosome 12q13–q15)
Q: Name the translocation in myxoid liposarcoma?
A: t(12;16) — creates FUS-DDIT3 fusion gene
Reference: Robbins & Kumar Basic Pathology; Schwartz's Principles of Surgery 11e; SRB's Manual of Surgery
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