Musculoskeletal & Skin Pathology MCQs

Pathology · 10 free questions with answers & explanations.

1. A 15-year-old boy presents with pain and swelling around the knee. X-ray shows a destructive lesion in the distal femoral metaphysis with periosteal elevation forming a triangular shadow at the margins. Biopsy shows a highly malignant spindle cell tumor producing osteoid directly from tumor cells. The most common site of distant metastasis is:
2. A 10-year-old boy has fever, leukocytosis, and a painful diaphyseal tibial mass. X-ray shows a permeative lytic lesion with an 'onion-skin' periosteal reaction. Biopsy shows sheets of small round blue cells with scanty cytoplasm. Flow cytometry shows positivity for CD99. Which chromosomal translocation is characteristically associated with this tumor?
3. A 55-year-old woman presents with knee pain, crepitus, and restricted range of motion. Joint fluid shows few cells (non-inflammatory). X-ray reveals asymmetric joint space narrowing, subchondral sclerosis, and osteophytes at joint margins. The primary pathologic process driving this condition is:
4. A 30-year-old woman presents with morning stiffness lasting over an hour, symmetrical small joint swelling of both hands, and elevated anti-CCP antibodies. Synovial biopsy shows villous hypertrophy, lining cell hyperplasia (pannus formation), and dense lymphoplasmacytic infiltrate. Which cytokine is the primary mediator of synovial destruction in this disease?
5. A 65-year-old man with chronic tophaceous gout has a white chalky deposit removed from the olecranon bursa. Microscopy with polarized light shows negatively birefringent needle-shaped crystals. The enzyme whose deficiency leads to secondary gout in Lesch-Nyhan syndrome is:
6. A 70-year-old woman presents with a pigmented skin lesion on her back that has been enlarging over 6 months. Dermoscopy shows irregular borders, color variegation, and a diameter of 8 mm. Biopsy reveals malignant melanocytes extending beyond the dermoepidermal junction into the papillary dermis. The single most important prognostic factor in this tumor is:
7. A 75-year-old farmer presents with a pearly, telangiectatic nodule with a rolled border on the nose. Biopsy shows tumor islands of basaloid cells with peripheral palisading and retraction artifact between tumor and stroma. This tumor is associated with mutations in which tumor suppressor gene, also mutated in basal cell nevus syndrome?
8. A 60-year-old man with actinic keratoses on sun-exposed skin develops a firm, indurated nodule on the lower lip that ulcerates. Biopsy shows nests of squamous epithelium with central keratin pearls and individual cell dyskeratosis invading into the dermis. The most important distinguishing feature from actinic keratosis is:
9. A 25-year-old woman presents with tense blisters on her trunk and extremities. Skin biopsy shows a subepidermal blister with the cleavage plane at the dermoepidermal junction. Direct immunofluorescence reveals linear deposits of IgG and C3 along the basement membrane zone. The target antigen is most likely:
10. A 40-year-old man presents with flaccid, easily ruptured blisters in the mouth and on the skin. Nikolsky sign is positive. Biopsy shows an intraepidermal blister with acantholysis (loss of intercellular bridges) just above the basal layer, with basal cells remaining attached to the dermis ('tombstone' pattern). Which immunofluorescence pattern confirms the diagnosis?