A Case of ALK+ Anaplastic Large-Cell Lymphoma With Aberrant Myeloperoxidase Expression and Initial Cutaneous Presentation.

Anaplastic large-cell lymphoma (ALCL) was first described in 1985 by Stein et al and is a clinically, morphologically, and immunophenotypically heterogeneous neoplasm characterized by ALK expression, rearrangement of the ALK gene, and most characteristically its occurrence in children. Clinically, cutaneous ALK+ ALCL can be divided into primary (cutaneous forms) and the much more common, secondary dissemination by a systemic lymphoma. Systemic ALK+ ALCL represents 10%-15% of childhood non-Hodgkin lymphoma and generally presents with advanced systemic disease. Here, we describe a case of a 9-year-old girl who presented with a solitary ulcerated nodule on the elbow that clinically resembled a pyogenic granuloma yet showed ALK, CD30, and myeloperoxidase expression. Fluorescent in situ hybridization with a break-apart probe for ALK revealed the presence of an ALK gene rearrangement. The initial workup showed no evidence of extracutaneous malignancy, and a diagnosis of primary cutaneous ALK+ ALCL was favored. Subsequent imaging studies revealed mediastinal lymphadenopathy, compatible with a systemic form of T-cell lymphoma, treated subsequently with chemotherapy. This report highlights the importance of an adequate systemic evaluation on the presentation of a cutaneous form of ALK+ ALCL.