Skin, Digital fibrokeratoma

Digital fibrokeratoma is a benign lesion of the skin on limbs or other extremities. Sections show acanthotic epidermis, covering fibrous dermal tissue, with dense collagen, parakeratosis, and a number of small blood vessels. Located in the digit, the diagnosis would be consistent with digital fibrokeratoma.

An interesting aspect of this case was the clinical suspicion for Koenen tumour (periungal fibroma), with the history of recurrent periungal skin over-growth. Associated with mutations in the TSC (tuberous sclerosis) gene, Koenen tumours generally cannot be distinguished from digital fibrokeratoma histologically. Presuming periungal location, the histology would be also in keeping with Koenen tumour, and the distinction is based predominantly on clinical findings (such as location, multiple lesions and history of tuberous sclerosis).