A healthy 30-year-old man presents with a 3-year history of an asymptomatic, fleshy papule at the base of his great toe. He denies any new lesions during this time, a history of trauma to the area, or a family history of similar skin lesions. He was treated previously by another dermatologist with cryotherapy; however, he returns to the clinic with recurrence of the lesion. Examination reveals a pedunculated, flesh-colored, well-demarcated tumor on the plantar surface of the base of his great toe.
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Acquired digital fibrokeratoma (ADFK) is a rare, benign, fibrous tumor that usually occurs as a solitary lesion in adults.1,2 This lesion has been reported in patients of all races aged from 12 to 70 years.1,3 Although it appears to be slightly more common in men, as of yet, too few cases exist to determine statistical significance.1,3
Trauma is thought to predispose individuals to the development of ADFKs; however, this lesion has also been reported in patients lacking a history of trauma.4 Other factors that may play a role in the development of ADFK include local factors that result in epidermal-dermal interactions, fibroblast-induced neoformation of collagen, and infectious causes.1,2,4
Clinically, ADFK presents as a small, solitary, well-defined nodule surrounded by a hyperkeratotic collar.1,2,5 The lesion presents most commonly on the fingers and toes, but in rare instances, it may also occur on the nose, lower lip, arms, and legs.2,6 Although the lesion is typically < 5 mm in size, a few cases of giant ADFK > 1 cm have been reported in the literature.1,2 Usually, the lesion is asymptomatic and is not associated with malignancy.1,6
Diagnosis is based on a combination of clinical and histopathologic features. Classic histologic features include a core of thick, densely packed collagen bundles oriented parallel to the longitudinal axis of the dermis.1,3,4,7 The epidermis is characterized by hyperkeratosis and irregular acanthosis, and the rete ridges are thickened and branching.7 Vessels of varying diameters are also scattered throughout the tumor, which is often highly vascular.3,7 Based on clinicohistopathologic findings, ADFK can be categorized into three different types.1,8 Classic dermoscopic findings include clumps of homogenous red lacunae divided by a white reticular septal wall.7 The adjacent skin is surrounded by telangiectasias.7
The differential diagnosis includes cutaneous horn, neurofibroma, pyogenic granuloma, supernumerary digit, and Koenen tumors.1,9 Although these lesions may appear similar clinically, they can be differentiated from ADFK through histology. For example, cutaneous horn lacks the prominent core of outgrowing connective tissue and often has epidermal neoplasia at the base; neurofibromas consist of loosely spaced spindle cells and wavy collagenous strands in the dermis, and supernumerary digits contain neural bundles in the dermis.1,9 Koenen tumors typically have atypical stellate myofibroblasts, are multilobulated, and are associated with tuberous sclerosis.1,5 In rare cases, ADFKs may also ulcerate and mimic aggressive neoplasms.8
The treatment of choice of ADFK is surgical excision, because these lesions do not spontaneously resolve.2,6 Recurrence is rare following complete excision.2,5,9
In our case, the patient was treated with complete surgical removal without recurrence at the 1-year follow-up visit.
Melinda Liu, BA, is a medical student and Maura Holcomb, MD, is a dermatology resident at Baylor College of Medicine in Houston.
- Ali M, Mbah CA, Alwadiya A, Nur MM, Sunderamoorthy D. Giant fibrokeratoma, a rare soft tissue tumor presenting like an accessory digit, a case report and review of literature. Int J Surg Case Rep. 2015; 10:187-190.
- Bulam H, Şencan A, Bozkırlı BA, Sezgin B, Tuncer S. Giant acquired periungual fibrokeratoma of the thumb: case report and review. Hand (N Y). 2015;10:140-142.
- Frydman AF, Mercer SE, Kleinerman R, Yanofsky VR, Birge MB. Acquired fibrokeratoma presenting as multiple plantar nodules. Dermatol Online J. 2010;16:5.
- Carlson RM, Lloyd KM, Campbell TE. Acquired periungual fibrokeratoma: a case report. Cutis. 2007;80:137-140.
- Longhurst WD, Khachemoune A. An unknown mass: the differential diagnosis of digit tumors. Int J Dermatol. 2015;54:1214-1225.
- Yu D, Morgan RF. Acquired digital fibrokeratoma: a case report. Ann Plast Surg. 2015;74:304-305.
- Hayashi K, Matori S, Kariya Y, et al. Dermoscopic observation of acquired digital fibrokeratoma developed on the dorsum of the fourth left toe. J Dermatol. 2016;43:107-108.
- Plaza JA, Suster S, Prieto VG, Sangueza M. Acquired reactive digital fibroma: a clinicopathologic report of 5 cases of a new entity. J Am Acad Dermatol. 2013;69:603-608.
- Choi JH, Jung SY, Chun JS, et al. Giant acquired digital fibrokeratoma occurring on the left great toe. Ann Dermatol. 2011;23:64-66.