A comparison of clinical, morphological and immunohistochemical features of lymphomatoid papulosis and primary cutaneous CD30(Ki-1)-positive anaplastic large cell lymphoma.

The advent of immunoperoxidase technique on paraffin embedded tissue has identified a number of shared immunologic markers present in various lymphoproliferative cutaneous disorders. Two such disorders are the recently described primary cutaneous CD30-positive anaplastic large cell lymphoma (ALCL) and lymphomatoid papulosis; both entities are characterized by CD30-positive large atypical cells predominantly of T cell origin. We have compared the clinical, morphological and immunohistochemical features of 50 patients with lymphomatoid papulosis to a group of 27 patients with cutaneous CD30-positive ALCL. There are clear differences between the clinical presentation in these two diseases, and although both are characterized by similar atypical cells, the histologic pattern and distribution of atypical cells is sufficiently different to allow distinction and specific diagnosis based on hematoxylin and eosin stained sections supported by the immunohistochemical stains. In addition, both diseases are characterized by a long benign course, rarely complicated by development of lymphoreticular malignancy and invariably demonstrate CD30 (Ki-1) antigen positive large atypical cells.