Abstract

We report a case of a 57-year-old female with liver failure who presented with a lesion on the right lower extremity. Histologic examination of the punch biopsy of the right lower extremity revealed a perivascular, interstitial, and peri-eccrine lymphocytic infiltrate, a patchy lymphocytic panniculitis composed of medium-to-large size lymphocytes rimming the adipocytes and infiltrating through the adipose tissue, and abundant necrosis. Additionally within the dermis and subcutaneous fat were nests of a well-differentiated squamous proliferation with keratin pearl formation. Immunohistochemical analysis revealed the atypical lymphocytes to be T-cells, exhibiting CD3 positivity and expressing CD8, CD56 and CD30. Granzyme and EBV in-situ hybridization stains were strongly positive. A Ki-67 highlighted multiple hotspots and clusters of staining cells (>70%). The immunophenotype was most compatible with extranodal natural killer/T-cell lymphoma, but the significance of the well-differentiated squamous proliferation remained unclear. A robust squamous metaplasia and hyperplasia of the eccrine units was favored given similar findings reported in other cases of extranodal NK/T-cell lymphoma in the literature. Given the already challenging nature of diagnosing extranodal NK/T-cell lymphoma, it is important for pathologists to know that these neoplasms can possibly induce pseudoepitheliomatous changes mimicking a second malignancy.