Although patients with mycosis fungoides (MF) typically experience an indolent disease course, a minority undergo a process of large-cell transformation (LCT), which often heralds more aggressive disease and shortened survival. Regrettably, most dermatologists are unfamiliar with LCT, and even fewer understand how to recognize it clinically. Because a diagnosis of LCT typically triggers more aggressive therapy and/or referral to cutaneous T-cell lymphoma (CTCL) centers, it is paramount for clinicians to be able to recognize suspect lesions visually.

LCT is diagnosed histologically; however, diagnostic biopsy is performed only if transformed lesions are suspected clinically. Because the literature provides little information on what clinical features should lead to suspicion of LCT, we sought to identify and categorize the presentations of LCT to aid in its recognition.

We identified 14 patients with biopsy-proven LCT confirmed by a board-certified dermatopathologist experienced with this diagnosis. The clinical presentations of LCT, timing of its evolution, and treatment regimens were evaluated by chart and photograph review.

We devised 3 categories that clinically represent LCT: (1) LCT occurring as a new, solitary nodule within a classic MF patch or plaque, (2) LCT occurring as abrupt onset of multiple scattered papules and/or nodules without spontaneous resolution, and (3) LCT occurring within new or enlarging tumors.

A larger number of reviewed cases might reveal additional clinical presentations of LCT.

Dermatologists may use our categories of clinical indicators to recognize and diagnose LCT earlier, allowing implementation of more aggressive treatment regimens when appropriate.