CD8-positive primary cutaneous anaplastic large T-cell lymphoma (PCALCL): case report and review of this unusual variant of PCALCL.

Primary cutaneous anaplastic large T-cell lymphoma (PCALCL) is a well-defined CD30-positive lymphoproliferative disorder with relatively good prognosis and response to treatment. We describe a case of PCALCL expressing CD8. The patient is a 57-year-old man that clinically presented with an ulcerated nodule in his left middle finger. Histopathologic sections showed an ulcerated epidermis with a diffuse lymphocytic infiltrate in the superficial dermis with focal epidermotropism. The large cohesive atypical cells were admixed with a reactive infiltrate composed of neutrophils, eosinophils, and small lymphocytes. Immunohistochemical studies showed the tumor cells to be strongly positive for CD8, CD30, and TIA-1, focally positive for CD3, and negative for CD4, CD20, CD56, Anaplastic Lymphoma Kinase (ALK-1), and HSV. Epstein-Barr virus by in situ hybridization was negative. The diagnosis of a CD8+ PCALCL was confirmed. There is limited precedent literature regarding CD8-positive PCALCL and this case falls within the clinical and histopathologic spectrum of CD30+ lymphoproliferative disorders. CD8/CD30 coexpression is rare in PCALCL and may have important clinical and prognostic implications. To the best of our knowledge there are only 4 previously reported cases describing similar findings.