Primary Cutaneous CD8+ T-cell Lymphoma, an Indolent and Locally Aggressive Form Mimicking Paronychia.

CD8 T-cell lymphomas comprise a wide spectrum of lymphomas, many which have yet to be formally classified. We present a case of a 43-year-old woman with an enlarging tumor distal to the distal interphalangeal joint of the fourth finger, compressing the underlying nail matrix. Magnetic resonance imaging showed bony involvement of the underlying distal phalanx. Histology showed a dense epidermotropic and pandermal infiltrate composed of medium-sized, uniformly pleomorphic lymphocytes with cleaved nuclei, which raised the possibility of primary cutaneous CD8 aggressive epidermotropic cytotoxic T-cell lymphoma. However, the patient's clinical photograph was inconsistent with this diagnosis. Other diagnoses, such as primary cutaneous acral CD8 T-cell lymphoma-a provisional entity, were also considered but did not capture all the features of this patient's lymphoma. We propose to classify this case as a primary cutaneous CD8 T-cell lymphoma, an indolent and locally aggressive form.