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Case Reports

Abstract

An 80-year-old man presented with numerous indurated violaceous plaques involving both lower extremities and the dorsum of his right wrist. He also had an ulcerated nodule on the left hip. His medical history was significant for low-grade follicular lymphoma that progressed to high-grade B-cell lymphoma (HGBCL) with MYC, BCL2 and BCL6 rearrangements (triple-hit lymphoma). He had received treatment with 6 cycles of R-mini-CHOP. 

Two skin biopsies were obtained. Histopathological examination of the right thigh plaque showed a dense dermal infiltrate of neoplastic cells that immunohistochemically and morphologically was consistent with his known HGBCL. The left hip lesion showed a dermal based infiltrate composed of mononuclear cells with irregular nuclear contours, distinct nucleoli, and moderate to abundant eosinophilic cytoplasm. Occasional nuclear grooves and multinucleated cells were seen. The mononuclear cells were positive for S100, CD1a, CD4, CD168, CD163, CD45, and CD43. These cells were negative for CD3, CD2, CD8, CD7, CD56, Lysozyme, CD68, CD123, CD57, CD21, CD30, MYC, CXCL13, PanMel, SOX10, MUM1, ERG, D2-40, PAX8, CK903, CMV, EBER, and CD35. B-cell markers were also negative. Ki67 was 60-70%. Fluorescent in situ hybridization (FISH) analysis of the hip lesion demonstrated MYC, BCL2, and BCL6 gene rearrangements. BRAF V600E mutation was negative. Given the positivity for Langerhans cell markers, in addition to histiocytic markers, a malignant histiocytic/dendritic cell neoplasm was favored. Moreover, the presence of the MYC, BCL2 and BCL6 rearrangements demonstrates the clonal relationship with the patient’s known HGBCL and suggests transdifferentiation in this rare clinical presentation.