19. Folliculotropic mycosis fungoides with cysts and comedones

Mycosis fungoides (MF) is the most common primary cutaneous T-cell lymphoma. Folliculotropic MF (FMF) is an uncommon variant, characterised by folliculocentric T-cell infiltrates. FMF shows a tendency towards more rapid progression than conventional MF and a relative resistance to skin targeted therapy, warranting its separation from conventional MF, which is reflected in the current WHO classification. The majority of cases of FMF present clinically with follicular papules, alopecia, mucinorrhoea and pruritis. In uncommon cases there can be an acneiform appearance. These cases show histological evidence of prominent milia, infundibular cysts and comedones. This uncommon form of an uncommon disease poses a significant diagnostic challenge, as there is close clinical and pathological mimicry of a number of benign folliculocentric inflammatory processes. We present a case of FMF with prominent follicular cysts, comedones and secondary granulomatous inflammation which was clinically and histologically mistaken for a benign process, including epidermal cyst, on two separate biopsies reported two years apart on two continents.