An otherwise healthy 5-month-old girl presents with an asymptomatic, rapidly growing, firm, smooth nodule on the side of her left fifth finger since she was 2 months of age.
An otherwise healthy 5-month-old girl presents with an asymptomatic, rapidly growing, firm, smooth nodule on the side of her left fifth finger since she was 2 months of age (Figure).
Diagnosis: Infantile digital fibroma (IDF)
Infantile digital fibromas (IDFs), also known as inclusion body fibromatosis or recurring digital fibrous tumors of childhood, are rare, benign, fibromatous tumors most commonly located on the dorsolateral aspects of the fingers and toes.1 These fibromas typically develop during the first year of life; however, they are present at birth in up to one-third of cases.2,3 In rare circumstances, they can appear during adulthood.4
Infantile digital fibromas initially exhibit a period of slow growth, which is followed by a rapid growth phase over 10 to 14 months.2 They can ultimately reach sizes ranging from 3 mm to 35 mm.5 They subsequently regress without treatment within 2 to 3 years.6
These fibromas classically appear as single to multiple, smooth, firm, skin-colored to pink nodules on the dorsolateral aspects of the fingers and toes.1,7 Interestingly, the thumbs and great toes are typically spared.1,2,7
Histopathologic examination reveals proliferations of spindle-shaped myofibroblasts admixed with collagen bundles within the dermis.1,7 The presence of eosinophilic inclusions arranged in a perinuclear fashion within the myofibroblast cytoplasm is pathognomonic for IDF. Masson’s trichrome stains these inclusions red, whereas phosphotungstic acidhematoxylin (PTAH) stains them purple.1
The differential diagnosis for IDF includes periungual fibromas, supernumerary digits, and acral fibrokeratomas.
Periungual fibromas are pink to skin-colored papules that develop from the proximal nail fold.1,8 They are associated with tuberous sclerosis and von Recklinghausen disease.8 In fact, approximately 50% of patients with tuberous sclerosis have multiple periungual fibromas, also known as Koenen tumors.1 However, solitary periungual fibromas can also be seen in the general population.8 They can produce pressure on the nail matrix, resulting in a longitudinal groove in the nail plate.1
Supernumerary digits are soft tissue growths that lack a skeletal component.1 They can appear as fleshy or verrucous-like papules, or present as larger, pedunculated nodules. Supernumerary digits are present at birth and often found bilaterally, with the most common location being the lateral aspect of the fifth finger.
Acral fibrokeratomas, also known as acquired digital fibrokeratomas, are relatively rare, benign skin growths.1,9 They present as skin-colored to pink, faintly keratotic papulonodules. Acral fibrokeratomas are typically solitary and tend to occur on the fingers and toes of middle-aged adults. They also can be seen on the palms and soles.9
Currently, there is no agreed-upon treatment approach for IDFs. Surgical excision is a viable option; however, recurrence is common with an estimated recurrence rate between 61% to 74%.3 Therefore, surgical excision is typically reserved for symptomatic cases causing pain or functional impairment.
Nonsurgical options include topical steroids, intralesional triamcinolone, or intralesional 5-fluorouracil (5-FU).3 However, these nonsurgical approaches have not been studied extensively, given the rarity of this condition. Eypper and colleagues recently proposed a management algorithm for IDFs: If symptomatic, proceed to surgical excision; if asymptomatic but greater than 1 cm, treat with intralesional triamcinolone or intralesional 5-FU; if asymptomatic and less than 1 cm, continue to monitor.
A shave biopsy confirmed the diagnosis of IDF in this infant girl. The growth continued to rapidly enlarge, causing slight distortion of the distal interphalangeal joint. Surgical excision was performed at the age of 14 months without complication. However, at age 3 years the patient returned to the clinic for evaluation of a new growth on the dorsolateral aspect of her distal left fourth finger, clinically consistent with IDF. There also was evidence of recurrence of the previously excised IDF on her left fifth finger.
Given the small size of these growths (both less than 1 cm), clinicians opted to closely monitor the patient and prescribed clobetasol 0.05% cream to be used 2 times daily on the affected areas.
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