Sarcomatoid variant of anaplastic large cell lymphoma mimicking a primary breast cancer: a challenging diagnosis.

The sarcomatoid variant of anaplastic large cell lymphoma is one of the rarest histologic variants of this neoplasm. Due to its sarcomatoid features, it is frequently misdiagnosed as a poorly differentiated sarcoma, anaplastic carcinoma, or melanoma. We report the case of a 92-year-old woman with a sarcomatoid anaplastic large cell lymphoma mimicking a primary breast neoplasm. The patient presented with a rapidly enlarging lump in the left breast and nodules in the right axilla. The immunohistochemical profile showed reactivity for leukocyte common antigen, UCHL-1, vimentin, and CD30, but immunoexpression of anaplastic lymphoma kinase was lacking. Anaplastic large cell lymphomas are lymphoid neoplasms of T-cell/null-cell lineage that consistently express the activation marker CD30 and usually carry a gene rearrangement of the anaplastic lymphoma kinase gene. To the best of our knowledge, this is the first reported case of sarcomatoid anaplastic large cell lymphoma presenting as a primary breast neoplasm in which anaplastic lymphoma kinase expression was assessed.