A case of primary cutaneous CD30+ anaplastic large cell lymphoma, small cell variant

Primary cutaneous anaplastic large cell lymphoma (PCALCL) is a rare cutaneous T-cell lymphoma. Most cases are composed of large anaplastic cells. However, it presents a wide spectrum of histologic patterns. In the small cell variant, a small-sized pleomorphic cell morphology can be seen. A 74-year-old woman presented with an 8-month history of asymptomatic ulcerative plaque and satellite nodule on the right calf. Her past medical history was not specific. The histologic findings on punch biopsy specimens showed a malignant small round cell tumor on both lesions. The tumor cells had large pleomorphic nuclei with multinucleation and some eosinophilic cytoplasm. We performed immunohistochemical staining to rule out neuroectodermal tumor, neuroendocrine tumor, melanoma, lymphoma, and so on. However, the staining results were negative for pancytokeratin, CD3, CD20, CD99, chromo- granin A, synaptophysin, CD56, ALK, HMB45, desmin, kappa, lambda, myoglobin, and S-100 protein. CT, MRI, and PET-CT were negative for extracutaneous involvement. Total excision was done, and additional immunohistochemical staining was performed to confirm the origin of the tumor. Staining results for vimentin, LCA, CD4, and CD30 were positive. We concluded that these findings were consistent with the small cell variant CD30+ PCALCL, which occurs rarely.