Acquired Digital Fibrokeratoma

In most cases, acquired digital fibrokeratoma presents as an asymptomatic protuberance that does not show spontaneous regression.[4] Clinically, it occurs as a solitary, skin-colored, and well-defined papule with a characteristic hyperkeratotic collarette at its base.[15] It usually occurs on the fingers and toes but can also be seen on the lower lip, nose, elbow, pre-patellar area and periungual tissue.[1][7] The size of the lesion is generally less than 1 cm, but there are reported cases of ADFK more than 1 cm. The lesions were designated as giant ADFKs.[7][3]

The dermoscopic features of acquired digital fibrokeratoma have been rarely investigated and may differ among ADFK cases. Rubegni et al. reported a central homogeneous pale-yellow core fringed by a hyperkeratotic white scaly collarette. These features may reflect the epidermal acanthosis, hyperkeratosis, and the presence of dense collagen fibers. More peripherally, a whitish-yellow area with dotted vessels was evident, while globular vessels externally encircled the whole tumor.[16] Hayashi et al. Reported the presence of red clumped structures divided by white meshwork-like keratotic septa, which may reflect the histologically retracted epidermis.[17]

There are reports of diverse therapeutic options, including cryotherapy, shave excision, curettage, and cauter. However, surgical excision is the mainstay of effective treatment. The tumor should be excised from its basal attachment to prevent recurrences.[18][19]

It is important to know about the various causes of cutaneous lesions mimicking acquired digital fibrokeratoma so that treatment can commence promptly. The differential diagnosis of ADFK includes supernumerary digit, verrucae vulgaris, cutaneous horn, neurofibroma, and pyogenic granuloma.[7][8][20]

Supernumerary digit, usually found at the base of the fifth finger is one of the most common hereditary limb malformations. Histologically, rudimentary polydactyly differs from ADFK by the presence of nerve bundles and neuroid elements.[5] ADFK can often be mistaken as supernumerary digit as seen in a case reported by  M. Ali et al., in which the histological report confirmed ADFK of the big toe.[7]

Verrucae vulgaris, also known as common warts, is the most frequently occurring neoplasm of the hand and fingers and is caused by human papillomavirus types 1, 2, 4, and 29.[21] Clinically, common warts often feature a pattern of tiny black dots that correspond to thrombosed capillaries.[22] Yu and Morgan reported a case in which ADFK was misdiagnosed as common warts and recurred after cryotherapy.[8]

A cutaneous horn is a clinical diagnosis referring to an exophytic and hyperkeratotic growth that contains a column of keratin. Histological examination may show a premalignant or malignant underlying process. Cutaneous neurofibromas are benign tumors that may share a clinical resemblance with ADFK and presents as a soft, polypoid, dome-shaped tumor.[23] Histological examination shows loosely spaced spindle cells, wavy collagenous strands, and myxoid matrix.[4][24]

Pyogenic granuloma is a common vascular tumor that usually occurs in areas of minor trauma.[25] Clinically, it presents as a friable, dome-shaped or pedunculated nodule with a scaly collarette. Differential diagnosis may also include superficial acral myxoma, periungual fibroma, and non-pigmented eccrine poroma.[26][27]

Acquired digital fibrokeratoma is a benign tumor with no risk of malignant transformation. Surgical excision is curative with a low risk of pain, bleeding, and infection. Excellent functional recovery with a satisfying cosmetic result is the expectation after complete surgical treatment. Usually, there is no recurrence.[19]

No reports exist of severe complications. However, a rare variant of acquired digital fibrokeratoma, known as periungual fibrokeratoma may cause nail plate deformity and affect the function of the digit.[15]

Patient education can include instructions to reduce the risk of infection.

The majority of skin lesions first present to primary care providers, including nurse practitioners. However, the number of cutaneous lesions is vast, and the primary care provider can't know all of them. Thus, it is important to work in collaboration with a dermatologist when faced with an unknown skin lesion. The other important fact is that one should not presume that all skin lesions are benign; missing a malignancy can prove to be devastating for the patient.

Acquired digital fibrokeratoma is most commonly diagnosed based on history and physical examination. Clinicians need to be familiar with unusual manifestations and other skin conditions that may simulate ADFK. Microscopic assessment is often required to provide histological diagnosis and variants. Management of ADFK is possible with a complete surgical excision performed by a dermatologist or a plastic surgeon. The postoperative period involves nurses for incision care and pharmacists for appropriate pain management that could significantly affect the patient's quality of life. If either the pharmacist or the nurse detects any failure in treatment or followup, they must report this to the treating physician. Just because acquired digital fibrokeratoma is a benign lesion, does not mean that the principles of interprofessional team dynamics are not in play, as they will always lead to better patient outcomes. [Level V]