Skin, soft tissue and paediatric tumours

13 NEET-PG practice questions on Skin, soft tissue and paediatric tumours, part of Pathology. The first 13 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

1. Question 1 · Easy

   A 61-year-old man has a 1.5 cm irregular, variegated pigmented lesion on his back excised at a district hospital. Histology confirms a superficial spreading melanoma without ulceration, and no lymph nodes are palpable. Which single histological measurement best predicts his prognosis?

   1. AClark level of invasion
   2. BBreslow thickness
   3. CDensity of tumour lymphocytes
   4. DLesion diameter

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   Answer: B · Breslow thickness

   Breslow thickness, measured in millimetres from the granular layer of the epidermis to the deepest invasive tumour cell, is the most important prognostic factor in localised melanoma. It sets the T stage, the width of the re-excision margin and whether sentinel lymph node biopsy is offered. Ulceration also worsens the prognosis. Clark level is no longer used in current staging.

   • A: Clark level describes anatomical depth and has been dropped from current staging.
   • C: Tumour-infiltrating lymphocytes have a minor prognostic role compared with thickness.
   • D: Diameter is used to raise suspicion clinically but does not predict outcome after excision.

2. Question 2 · Easy

   A 2-year-old girl is brought to the gynaecology OPD in Varanasi with blood-stained discharge and a soft, polypoid mass like a bunch of grapes protruding from the vagina. Biopsy shows small round to spindle tumour cells crowded beneath the surface epithelium as a dense 'cambium layer', staining for desmin and myogenin. The diagnosis is:

   1. AYolk sac tumour of the vagina
   2. BEmbryonal rhabdomyosarcoma
   3. CClear cell adenocarcinoma
   4. DFibroepithelial polyp

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   Answer: B · Embryonal rhabdomyosarcoma

   A grape-like polypoid mass in the vagina or bladder of a young child, with a subepithelial cambium layer of desmin- and myogenin-positive cells, is the botryoid form of embryonal rhabdomyosarcoma (sarcoma botryoides). Embryonal rhabdomyosarcoma is the commonest soft tissue sarcoma of children, and the botryoid form has a relatively good prognosis with chemotherapy and conservative surgery.

   • A: Vaginal yolk sac tumour raises AFP and shows Schiller-Duval bodies, not skeletal muscle markers.
   • C: Clear cell adenocarcinoma affects young women, classically after in-utero DES exposure.
   • D: Fibroepithelial polyps lack a cambium layer of myogenin-positive cells.

3. Question 3 · Medium

   A 34-year-old man has a slowly growing, firm, reddish-brown plaque with protruding nodules on the skin of his upper back; it has recurred twice after simple excision at a local clinic. Biopsy shows uniform spindle cells in a storiform (cartwheel) pattern infiltrating deep into the subcutaneous fat in a honeycomb pattern, and the cells are strongly CD34-positive. If the tumour becomes unresectable, which drug targets its molecular driver?

   1. AVemurafenib
   2. BTrastuzumab
   3. CImatinib
   4. DCrizotinib

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   Answer: C · Imatinib

   A storiform spindle-cell tumour that honeycombs into the subcutaneous fat and is strongly CD34-positive is dermatofibrosarcoma protuberans. Most carry a COL1A1::PDGFB fusion, usually from t(17;22), which drives overproduction of PDGF-B and constant activation of the PDGF receptor. Imatinib inhibits this receptor tyrosine kinase and is used for unresectable or metastatic disease. The tumour sends finger-like extensions far beyond the visible edge, so it recurs after simple excision and needs wide or Mohs excision.

   • A: Vemurafenib inhibits mutant BRAF V600E, used in melanoma.
   • B: Trastuzumab targets HER2 in breast and gastric cancer.
   • D: Crizotinib inhibits ALK and ROS1 fusions in lung cancer.

4. Question 4 · Medium

   A 48-year-old woman had a melanoma excised from her upper back 3 years ago. She now has multiple liver and lung metastases. Molecular testing of a metastasis shows a BRAF V600E mutation. Which targeted treatment is directed at this abnormality?

   1. ATrastuzumab
   2. BCetuximab
   3. CDabrafenib with trametinib
   4. DImatinib

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   Answer: C · Dabrafenib with trametinib

   BRAF V600E keeps the MAPK pathway switched on and is found in about half of cutaneous melanomas. A BRAF inhibitor combined with a MEK inhibitor, such as dabrafenib with trametinib, gives better responses than a BRAF inhibitor alone and reduces the skin squamous cell carcinomas that BRAF inhibitors cause by paradoxical MAPK activation. Immune checkpoint inhibitors (anti-PD-1, with or without anti-CTLA-4) are the other main first-line option.

   • A: Trastuzumab targets HER2 in breast and gastric cancers.
   • B: Cetuximab blocks EGFR and is used in colorectal and head and neck cancers.
   • D: Imatinib targets KIT, which is mutated in some acral and mucosal melanomas, not BRAF.

5. Question 5 · Hard

   A 15-year-old boy has a rapidly enlarging, painless 6 cm mass in the soft tissue of the left forearm, with an enlarged axillary lymph node. Biopsy shows small round blue cells clinging to fibrous septa, with central loss of cohesion that creates spaces resembling lung alveoli. Immunohistochemistry: desmin positive, myogenin strongly and diffusely positive, CD99 negative, synaptophysin negative, and CD45 (LCA) negative. Which translocation is most likely present?

   1. At(2;13) PAX3::FOXO1
   2. Bt(12;16) FUS::DDIT3
   3. Ct(11;22) EWSR1::FLI1
   4. Dt(X;18) SS18::SSX

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   Answer: A · t(2;13) PAX3::FOXO1

   The panel first places the tumour among the small round blue cell tumours: CD45-negative excludes lymphoma, synaptophysin-negative excludes neuroblastoma, CD99-negative argues against Ewing sarcoma, and desmin with myogenin shows skeletal muscle differentiation. An alveolar pattern in an adolescent's limb with strong, diffuse myogenin is alveolar rhabdomyosarcoma, which usually carries t(2;13) PAX3::FOXO1 or, less often, t(1;13) PAX7::FOXO1. Fusion-positive tumours have a worse prognosis than embryonal rhabdomyosarcoma, and early nodal spread is common.

   • B: FUS::DDIT3 defines myxoid liposarcoma in adults.
   • C: EWSR1::FLI1 defines Ewing sarcoma, which is CD99-positive and myogenin-negative.
   • D: SS18::SSX defines synovial sarcoma, a spindle-cell tumour without myogenin.

6. Question 6 · Hard

   A 59-year-old man has had abdominal fullness for 6 months. CT shows an 18 cm mostly fatty retroperitoneal mass with a few thick septa, displacing the right kidney. The resected tumour is yellow and lobulated; histology shows mature-looking adipocytes that vary in size, with scattered enlarged, hyperchromatic stromal cells in fibrous septa. Which test best confirms the diagnosis?

   1. AImmunostaining for S-100 protein
   2. BImmunostaining for desmin
   3. CRT-PCR for FUS::DDIT3 fusion
   4. DFISH for MDM2 amplification

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7. Question 7 · Medium

   A child with absent irises since birth, hypospadias with undescended testes and developmental delay is now found to have a large flank mass. Consider: 1. The syndrome results from a deletion at 11p13. 2. The tumour is typically triphasic, with blastema, stroma and epithelium. 3. Diffuse anaplasia carries a worse prognosis. 4. Nephrogenic rests are precursor lesions. Which of these statements are true?

   1. A1 and 2 only
   2. B1, 3 and 4 only
   3. C2 and 3 only
   4. D1, 2, 3 and 4

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8. Question 8 · Medium

   Biopsy of a deep, painful mass behind the knee in a college athlete shows a biphasic tumour: gland-like epithelial structures among fascicles of uniform spindle cells, with calcifications. Immunostains: nuclear TLE1 positive, cytokeratin and EMA focally positive, CD34 negative. Which translocation is characteristic?

   1. At(X;18) SS18::SSX
   2. Bt(2;13) PAX3::FOXO1
   3. Ct(11;22) EWSR1::FLI1
   4. Dt(12;16) FUS::DDIT3

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9. Question 9 · Hard

   Abdominal CT of an engineering student with abdominal distension, early satiety, constipation and weight loss of 7 kg over 3 months: many peritoneal masses of different sizes and ascites, with no organ of origin and normal liver and kidneys. Serum AFP, hCG and CA-125 are normal, and testicular ultrasound is normal. A peritoneal biopsy shows well-defined nests of small round blue cells separated by dense desmoplastic stroma. Immunostains: cytokeratin positive, desmin positive in a perinuclear dot-like pattern, WT1 (C-terminal antibody) nuclear positive, myogenin negative, and CD99 weak. Which gene fusion defines this tumour?

   1. AEWSR1::FLI1
   2. BEWSR1::WT1
   3. CPAX3::FOXO1
   4. DSS18::SSX

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10. Question 10 · Medium

    At the ART centre, a truck driver with HIV (CD4 count 90 cells/µL) who stopped treatment a year ago has violaceous plaques on both legs and on the hard palate. Skin biopsy shows slit-like vascular spaces lined by spindle cells, extravasated red cells and haemosiderin. Which immunostain confirms the diagnosis?

    1. AHHV-8 LANA-1
    2. BFactor XIIIa
    3. CDesmin
    4. DS100 protein

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11. Question 11 · Easy

    On the sole of a farmer from Mandya, an irregular brown-black patch with uneven borders has spread slowly over 3 years, and a raised nodule has now appeared in it. Biopsy shows atypical melanocytes along the basal layer with a nodule invading the dermis. Which melanoma subtype is this?

    1. ASuperficial spreading
    2. BLentigo maligna
    3. CAcral lentiginous
    4. DDesmoplastic

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12. Question 12 · Medium

    A firm, reddish-brown plaque on the chest wall of a bank clerk has slowly grown over 6 years and developed protruding nodules; it came back after a simple excision. Histology shows uniform spindle cells in a storiform (cartwheel) pattern infiltrating the subcutaneous fat in a honeycomb fashion. CD34 is strongly positive and factor XIIIa is negative. Which gene fusion drives this tumour?

    1. ASS18::SSX
    2. BNAB2::STAT6
    3. CETV6::NTRK3
    4. DCOL1A1::PDGFB

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13. Question 13 · Medium

    Urine vanillylmandelic acid and homovanillic acid are raised in a toddler with an abdominal mass crossing the midline, bluish periorbital bruising and irritability. Adrenal biopsy shows sheets of small round blue cells forming Homer Wright rosettes around fibrillary neuropil. Which finding predicts the worst prognosis?

    1. AHyperdiploid tumour DNA
    2. BAge under 18 months
    3. CMYCN amplification
    4. DSchwannian stroma-rich histology

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