FRCPath Haem Part 1 MCQs-Morphology 480

A 46-year-old man presents with recurrent flushing, abdominal discomfort, pruritus and episodes of unexplained hypotension. He has mild hepatosplenomegaly.

FBC shows:

• Hb: 108 g/L

• WBC: 9.8 × 10⁹/L

• Platelets: 165 × 10⁹/L

A bone marrow aspirate is haemodiluted. The trephine biopsy shows fibrosis, particularly around trabeculae. There is trabeculae thickening and distortion

Immunohistochemistry demonstrates strong expression of CD117. The cells show aberrant CD25 expression.

Which of the following is the single most likely diagnosis?

A. Mast cell activation syndrome

B. Systemic mastocytosis

C. Acute myeloid leukaemia

D. Chronic myeloid leukaemia

E. Systemic mastocytosis with associated neoplasm