CD30‐Positive Peripheral T‐Cell Lymphoma

A 47 year‐old female presented with a five‐month history of left lower extremity cellulitis which was refractory to oral antibiotics. Physical exam revealed focal erythema of the left lower extremity and left inguinal adenopathy. A left leg skin punch biopsy revealed a dense infiltrate present primarily within the deep dermis consisting of markedly atypical large cells with prominent nuclear pleomorphism and focal multinucleation. Many of the cells displayed “horseshoe shaped” or “donut shaped” nuclei, consistent with so‐called hallmark cells and/or wreath cells. Scattered mitoses were also observed. Imunohistochemical stains for CD45 and vimentin were positive. Stains for cytokeratins AE1/AE3, CK7, desmin, and S‐100 protein were negative. The CD45‐positive population was also positive for CD3, CD30, CD45 Ro, and epithelial membrane antigen. They were negative for CD20, CD15, and CD43. A biopsy of the left inguinal lymph nodes revealed involvement by a morphologically similar neoplasm with an identical immunohistochemical staining pattern. Additionally, a CD56 and ALK‐1 stain were performed on the lymph node biopsy, and both were negative. This neoplastic process represents a CD30‐positive peripheral T‐cell lymphoma. The differential diagnosis includes an ALK‐1‐negative anaplastic large cell lymphoma and a primary cutaneous CD30‐positive T‐cell lymphoproliferative disorder.