Acquired digital fibrokeratoma
Department of Skin and STD, Kasturba Medical College, Manipal
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Salim T, Balachandran C. Acquired digital fibrokeratoma. Indian J Dermatol Venereol Leprol 2001;67:273
A 56- year-old man, agriculturist by occupation presented to the Dermatology out patient department of Kasturba Hospital, Manipal with a 10 year history of an asymptomatic firm finger-like growth (18mm x 7mm) over the antero-medial aspect of the proximal phalanx of right finger [Figure - 1]. The size of the lesion increased slowly for the initial 2-3 years, later it stabilized, but did not regress. There was no history of trauma prior to the onset of the lesion. It was not painful nor did it itch or bleed even after further trauma. The lesion was excised and histopathologic examination revealed marked hyperkeratosis and acanthosis with thick interwoven bundles of collagen forming a central core. The collagen bundles were arranged in the vertical axis of the lesion. Numerous proliferating fibrobalsts were seen in between the collagen bundles. The findings were suggestive of acquired digital fibrokeratoma (ADFK).
ADFK is an uncommon benign lesion of unknown cause that is usually found on the fingers and toes. It is occasionally found on palms and soles. It was mentioned by Monocorps and Flare, and described by Bart et al as a separate clinical entity. It affects males more often than females. Pavithran was first to report a case of ADFK in Indian literature. The exact pathogenesis of this lesion is unknown. Trauma is often thought to be a predisposing factor, but case histories do not seem to support this concept. It is presumed that trauma or some local factors results in epidermo-dermal interaction and fibroepithelial tumours Lesions are usually dome shaped though they may be elongated finger-like projection as seen in our case. They are almost always solitary, seen in adults and are not usually curative.
Recently Kint et al described three histologic variants after reviewing 50 cases of ADFK. The most common type described, as reported by Bart et al, has findings similar to our case. The secound variant has an increase of firbroblasts along the vertical axis of the tumor and a marked decrease in elastic fibres; and the third type has oedematous connective tissue and separation of collagen bundle with few elastic fibres.
Differential diagnoses include cutaneous horn, pyogenic granuloma, and supernumerary digit. Although horn resembles ADFK clinically, it does not have a prominent core of out growing connective tissue and often shows edidermal neoplasia at the base. Supernumerary digits, usually seen at the base of the 5th dioit, are present at birth and may be bilateral. Pyogenic granulomas usually have a more consistent relationship to trauma, are more friable and histologically are distinct in the early stages. However, as a pyogenic granuloma matures, increased fibrosis and decreased vascularity may make histologic differentiation difficult.
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