Interdigital melanoma, as a subtype of acral lentiginous melanoma, is relatively uncommon in the Caucasian population. It frequently goes unrecognized for a prolonged period of time prior to diagnosis, due to its asymptomatic nature and variable clinical appearance.
We report the case of a 67-year-old Caucasian woman who presented with interdigital malignant melanoma affecting two neighboring interdigital spaces. It had evolved over a period of more than 15 years and had been initially misdiagnosed as tinea pedis due to the macerated appearance of the lesion and a positive mycologic examination.
We highlight the striking involvement of two adjacent interdigital spaces and the neighboring area of the sole of the foot by the tumor. The melanoma was staged as IIIC, with pathologic grading T4bN2bM
The involvement of two adjacent interdigital spaces is unusual and, to our knowledge, has not been previously highlighted in the medical literature. It may be explained, in part, by the longstanding nature of the lesion in our patient.