Abstract

Unilesional, or solitary, mycosis fungoides (MF) is an uncommon but well-documented subtype of MF which presents clinically and histopathologically similar to classic MF. Unlesional and classic MF typically demonstrate marked epidermotropism. A 67-year-old female with a past medical history of melanoma presented with a 9 month history of an asymptomatic but non-healing lesion on the left abdomen. The area had not grown and does not involve other anatomic locations. The patient denied new or changing medications or changes in her health. She denied any new or preceding contactants to the area. On exam there was a 1.5cm erythematous, non-blanching, non-tender patch; the patch did not exhibit scale or crinkling atrophy. The remainder of the skin exam was unremarkable.  Saucerization biopsy was performed and demonstrated a brisk lichenoid infiltrate with focal and sparse epidermotropism of enlarged, atypical appearing CD4+ lymphocytes. TCR Beta Clonality assay demonstrated a clonal T cell receptor gene rearrangement in a polyclonal background. Given lack of history to suggest a contact reaction or drug exposure, a pseudolymphomatoid reaction was deemed unlikely. The patient’s presentation was most consistent with unilesional mycosis fungoides. The patient was started on triamcinolone 0.1% cream twice per day. We present an unusual case of unilesional MF that, unlike most other documented cases which are indistinguishable from classic MF, presented with minimal epidermotropism. Distinguishing unilesional MF from other subtypes has important clinical implications, as previous studies have shown unilesional MF has an excellent prognosis as compared to other MF subtypes.