PMC8245761_01
Bluish-black plaque with central atrophy on the left back of the patient.
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Physical examination showed a 30 x 25 mm asymptomatic, smooth, bluish-black plaque with central atrophy ( Figure 1 ).
Histopathologic and immunohistochemical analyses of atrophic pigmented DFSP. (A, B) Proliferation of spindle cells in dermis and scattered pigmented cells (hematoxylin and eosin, 100x and 200x magnification). (C, D) Diffuse and strong expression of CD34 (100x and 200x magnification). (E, F) Pigmented cells positive for S100 (100x and 200x magnification). PDGFB and COL1A1 gene fusion was detected by FISH (F, insert, white arrow).
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Cells containing brown pigment were scattered in the dermis and subcutaneous tissue ( Figures 2A, B  ). Immunohistochemical analysis showed that the spindle cells were positive for cluster of differentiation CD34 ( Figures 2C, D  ) and vimentin but negative for CD68, cytokeratin, desmin, and S100. The pigment-containing cells were positive for S100 ( Figures 2E, F  ) but negative for CD34. The collagen, type I, alpha 1 (COL1A1)-platelet-derived growth factor subunit B (PDGFB) fusion gene was detected by fluorescence in situ hybridization ( Figure 2F , insert).
Magnetic resonance imaging of atrophic pigmented DFSP showed a well-circumscribed plaque with adjacent tissue thinning in the left region of the trunk. (A) T1-weighted images revealed a slightly higher non-uniform signal, (B) while T2-weighted images showed a high signal.
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T2-weighted images showed a high signal ( Figures 3A, B  ). The patient was treated by wide local excision with 3-cm margins and reconstruction with a full-thickness skin graft. The patient has been regularly followed up for 7 months with no recurrence.