Malignant Dendritic Cell Sarcomas in the Skin: 2 Cases of Rare Sarcoma Subtypes With Literature Review

Interdigitating dendritic cell sarcoma is a rare, aggressive hematological malignancy primarily originating in lymph nodes, with only 10 reported cases presenting in the skin (primary cutaneous interdigitating dendritic cell sarcoma). Past presentations showed erythematous nodules on the proximal extremities, back, or face. Morphologically, these neoplasms are similar to melanomas and other dendritic cell (DC) tumors, making their diagnosis difficult. Here, we present 1 case of primary cutaneous interdigitating dendritic cell sarcomas and another 1 of malignant indeterminate dendritic cell tumor (indeterminate DC sarcoma). The first case is an 83-year-old man who presented with recent ulceration and bleeding of an asymptomatic, slow growing lesion on his right thigh with biopsy revealing a large, well-circumscribed polypoid spindle cell tumor in the dermis with atypical cells with vesicular nuclei in a lymphoplasmacytic background and immunohistochemistry positivity for CD45, CD68, S100, and Cyclin D1. The second case is a 74-year-old man who presented with a progressively darkening and enlarging abdominal skin lesion with biopsy revealing a diffuse infiltrate of atypical poorly differentiated pleomorphic nuclear cells and immunohistochemistry positivity for S100, CD1a, CD56, CD43, cyclin D1, CD31, CD4, and BRAF V600E. Our findings contribute to expand the reported literature on primary cutaneous DC sarcomas.