What Is the Growth on This Man’s Finger?

Answer: Acquired Digital Fibrokeratoma

Acquired digital fibrokeratoma (ADF), sometimes called acral fibrokeratoma, is an uncommon but benign skin lesion that predominantly occurs on the fingers and toes and is often associated with some degree of remote trauma. It is more commonly seen in men, and it often presents in middle age.

The morphology of ADF lesions can vary from a flesh-colored, well-circumscribed, dome-shaped plaque to a firm, fingerlike projection.1 Typically, the surface texture is smooth, but there can be some verruciform topography that may place warts or cutaneous horn high on the differential.

ADF at the distal digit may be mistaken for periungual fibroma (Koenen tumors), but clinical correlation, especially in the context of tuberous sclerosis, helps to guide diagnosis, given that periungual fibromas occur in nearly 50% of persons with tuberous sclerosis.2,3 One of the hallmarks of ADF is the hyperkeratotic collarette present at the base of the lesion that sometimes has a scaly appearance.

Microscopically, the polypoid lesion may have thick, dense, vertically oriented collagen fibers and elastic fibers with normal to substantial dermal proliferation of stellate fibroblasts.4 Larger lesions will have a well-established vascular supply, but nerve tissue is either absent or inconspicuous.5 The epidermis also may have variable presentation, but classic features include a varying degree of papillomatosis with acanthosis and orthokeratosis.

Although the ADF lesion is benign, possible secondary complications may warrant removal, such as reduction in range of motion of the adjacent joint, or cosmetic/aesthetic discontent. While there is no single well-established modality to remove the ADF, numerous destructive procedures are accepted in the dermatologic community. Perhaps the most common form of lesion destruction is, coincidentally, a shave biopsy to confirm the diagnosis. It should be noted that there is an inherent risk of return of the lesion, especially in the periungual areas of the toes.6 Other procedures used for ADF resolution include cryotherapy, curettage, cauterization, and surgical excision (to include full-thickness excision with secondary intention healing).7

Outcome of the case. After a shave biopsy to confirm the diagnosis, the patient was informed of the benign nature of the ADF based on clinical and histologic examination findings. He followed up 6 months later with minimal scarring at the shave site and no recurrence. He was advised to follow up as needed.

DISCLAIMER:
The views expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Department of the Navy, the Department of Defense, or the US Government.

REFERENCES:

1. Baykal C, Buyukbabani N, Yazganoglu KD, Saglik E. Acquired digital fibrokeratoma. Cutis. 2007;79(2):129-132.
2. Quist S, Franke I, Sutter C, Bartram CR, Gollnick HP, Leverkus M. Periungual fibroma (Koenen tumors) as isolated sign of tuberous sclerosis complex with tuberous sclerosis complex 1 germline mutation. J Am Acad Dermatol. 2010;62(1):159-161.
3. Kint A, Baran R. Histopathologic study of Koenen tumors: are they different from acquired digital fibrokeratoma? J Am Acad Dermatol. 1988;18(2 pt 1):369-372.
4. Kint A, Baran R, De Keyser H. Acquired (digital) fibrokeratoma. J Am Acad Dermatol. 1985;12(5 pt 1):816-821.
5. Choi JH, Jung SY, Chun JS, et al. Giant acquired digital fibrokeratoma occurring on the left great toe. Ann Dermatol. 2011;23(1):64-66.