Cutaneous gamma-delta T-cell lymphoma with central nervous system involvement: report of a rarity with review of literature.

Primary cutaneous gamma-delta (γδ) T-cell lymphoma is an extremely rare and aggressive variant of cutaneous lymphoma. Central nervous system (CNS) involvement, a rare finding, and hemophagocytic syndrome are two complications that are commonly fatal. We describe a 58-year-old patient presenting with skin plaque who subsequently developed subcutaneous nodules diagnosed as cutaneous T-cell lymphoma (CTCL), clinically resembling 'mycosis fungoides'. The patient was treated with repeat topical radiation therapies but had frequent relapsed disease. Approximately 4.5 years after, the patient presented with third and sixth cranial nerve palsies and was found to have CNS involvement by lymphoma per positron emission tomography-computed tomography (PET/CT) and a biopsy of foramen magnum. Phenotypically, the tumor cells were CD3(+)/CD4(-)/CD8(-)/CD7(+)/CD5(-)/CD30(-)/TCRαβ(-)/TCRγδ(+). Despite aggressive strategies taken, the patient expired 3 months after the diagnosis of the CNS lesion. A retrospective investigation proved the original CTCL to be γδ T-cell in origin, confirming an indolent cutaneous γδ T-cell lymphoma with eventual CNS manifestation. We present this case to draw attention to the entity, which can occasionally present with misleading histopathologic and clinical features. In addition, we provide a review of the literature to summarize clinical and pathologic features of the reported similar cases.