Disseminated dermal dendrocytomas. A new cutaneous fibrohistiocytic proliferative disorder?

A 77-year-old white woman presented with 1 1/2-year history of progressively enlarging cutaneous papules, nodules, and plaques, some of which had spontaneously regressed. Her past medical history included untreated chronic lymphocytic leukemia for 10 years' duration. Multiple skin biopsy specimens revealed a diffuse superficial and deep dermal spindle-cell infiltrate accompanied by occasional foamy round cells and multinucleated giant cells. The spindle-shaped cells were focally arranged in a storiform pattern with prominent fibrous stroma. The spindle-shaped cells stained positively for numerous macrophage markers including CD45, factor XIIIa, Leu M5, HLA-DR, CD4, and Leu M3, consistent with dermal dendrocytes. They were also positive for nonspecific esterase and acid phosphatase, which is typical of tissue macrophages. The spindle-shaped cells were negative for CD-1, S-100, and ATPase activity, thus excluding a Langerhans cell immunophenotype. Combining the clinical features, light microscopy, immunohistochemistry, and enzymatic analysis, this patient appears to represent a novel cutaneous fibrohistiocytic proliferative disorder that features large numbers of dermal dendrocytes.