PMC9918867_01
Multiple brown maculopapular skin rashes distributed over the trunk and extremities.
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F1
Physical examination showed a well-built gentleman with multiple brown maculopapular skin rashes, measuring 5-10 mm in diameter and present on the trunk and extremities (Fig. 1).
Skin punch biopsy showing neoplastic mast cells in the papillary dermis (H&E, x100).
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F2
A 4-mm skin punch biopsy revealed aggregates of neoplastic mast cells in the papillary dermis (>15 mast cells in the aggregates) (Fig. 2).
CD117 highlights the neoplastic mast cells.
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F3
The mast cells were positive for CD117 and negative for melanocytic markers (Fig. 3).
Mast cells from bone marrow aspirate smear: arrowed cells (a) and atypical mast cell (b) with kidney-shaped nucleus with mature chromatin, atypical spindle-shaped mast cell (c, d), and arrowed cells (e) and atypical mast cell (f) with hypogranular cytoplasm (Wright stain, original magnification x1,000).
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F4
There were approximately 1% mast cells, and the majority show abnormal morphology including a kidney-shaped nucleus, irregular granules distribution, hypogranulation, and spindle forms (Fig. 4).
a Bone marrow biopsy shows cellular marrow with trilineage hemopoiesis, H&E, x200. b Focal aggregate of mast cells, H&E, x100. c Focal aggregate of mast cells, many with abnormal morphology with kidney-shaped nucleus, H&E, x1,000. d CD117 highlights the mast cell aggregate, x1,000. e Many of the mast cells are spindle-shaped, as highlighted by CD117, x1,000. f CD25 shows aberrantly positive mast cells x1,000.
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F5
Based on these findings (Fig. 5), bone marrow involvement by systemic mastocytosis was concluded.