Primary anaplastic large-cell lymphoma of the skin. A case report suggesting that regressing atypical histiocytosis and lymphomatoid papulosis are subsets.

A patient with primary anaplastic large-cell lymphoma of the skin with characteristic clinical findings is described. The diagnosis was made on the basis of histologic and immunohistochemical findings. The phenotype of the tumor cells was not determined, but rearrangement of the T-cell receptor beta gene indicated that the tumor was of T-cell lineage. Despite high-grade malignancy of the tumor cells, the patient unexpectedly had a benign clinical course. The findings in this case suggest that regressing atypical histiocytosis and lymphomatoid papulosis type A are subsets of anaplastic large-cell lymphoma.