A case of primary cutaneous anaplastic large cell lymphoma with variant anaplastic lymphoma kinase translocation.

Anaplastic lymphoma kinase (ALK) is frequently observed in systemic anaplastic large cell lymphoma (ALCL), mostly in childhood or adolescence, but only rarely in primary cutaneous cases. We report a case of primary cutaneous ALCL (pcALCL) with cytoplasmic ALK expression. A 54-year-old woman with an ulcerative tumour on her forehead was admitted to our hospital. Histologically, there was an infiltrate consisting of atypical large lymphocytes and small lymphocytes in the dermis and fat tissue. Southern blot analysis showed monoclonal T-cell receptor Cbeta1 gene rearrangement. Atypical large lymphocytes were positive for CD30, CD4 and CD25, and negative for CD3 and CD79a. They were also positive for ALK only in the cytoplasm, and neurophosmin (NPM)-ALK fusion transcript was not detected by reverse transcription-polymerase chain reaction. This suggested that the translocation partner of the ALK gene in this case was different from NPM (variant translocation). The tumour on the forehead resolved in 1 month after biopsy. Nodular lesions recurred on the right knee, and were histologically identical with the forehead lesion. Our case suggests the existence of a subgroup with variant ALK translocation in pcALCL; examining NPM-ALK translocation in each case with ALK expression should be useful to characterize the disease further.