Acquired digital fibrokeratoma (ADFK) is a benign growth that is typically seen on the digits or the fingers and toes. It is also called acral fibrokeratoma. It is an uncommon condition and typically seen in middle age. The tumors are typically dome-shaped, but sometimes may look like finger-like projections.
Although the exact cause of this growth is poorly understood, it is believed to be caused by trauma or injury to the digits. It has been argued that trauma leads to epidermal-dermal interaction, which causes a fibroepithelial tumor development.
ADFK is usually seen as solitary lesions, but one or two cases have been reported where they were associated with another tumor.
The ADFK tumor appears as fibrous projections on the skin. It is usually flesh-colored or pink in appearance. A collarette of scaly skin can be found at the base of the projection which helps in diagnosis. The overlying skin of the tumor may be thickened.
Researchers have described ADFK as a well-defined tumor with a hyperkeratotic collar at its base. The tumor protrudes from the skin surface just like a hernia.
ADFK tumor is typically less than 1 cm in size and only a few cases of ADFK have been reported with tumor sizes larger than 1 cm – about 3.2 × 3.8 × 1.5 cm and 2.5 × 1.6 × 1.4 cm - and they have been recorded as giant ADFKs.
The ADFK lesion is often mistaken as a supernumerary digit. Supernumerary digits are usually present at birth and seen at the base of the fifth digit. Diagnosis is generally confirmed using biopsy to differentiate ADFK from other isolated papules such as warts, aggressive digital papillary adenocarcinoma, periungual fibromas, and cutaneous horn.
Histologically, ADFK is distinguished by the presence of several nerve bundles at the base of the lesion. Differential diagnosis for ADFK include conditions such as pyogenic granuloma, viral warts, dermatofibroma, Koenen tumor of tuberous sclerosis, onychomatricoma, and neurofibromas. Neurofibromas are soft, skin-colored tumors with inner skin layer made up of collagenous strands and loosely packed spindle cells.
The hyperkeratotic base of the ADFK lesion helps differentiate it from a condition called garlic clove fibroma. It is very important to rule out any other potential causes of tumorous growth and confirm ADFK during diagnosis.
ADFK treatment typically involves removing the lesion surgically. No further treatment would be necessary as the lesion is benign. The excision of the tumor is made under general anesthesia.
To begin with, an incision is made around the tumor’s base. Then the incision is extended to the soft tissues, which are then dissected. The soft tissues generally do not contain any major blood vessels, nor is the tumor attached to bones. The tumor is then fully removed and the wound is left to heal.
On follow-up, there is usually no recurrence of the tumor. Periungual lesions which occur below proximal nail folds need to be removed with extra care so as not to cause any damage to the matrix, as that can lead to irreversible nail dystrophy.