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
1. Bolognia JL, Jorizzo JL, Schaffer JV, et al. Dermatology, 3rd ed. London: Elsevier Ltd; 2012:1009, 1144, 1964-1965, 1969-1970.
2. Heymann WR. Infantile digital fibromatosis. J Am Acad Dermatol. 2008;59(1):122-123.
3. Eypper EH, Lee JC, Tarasen AJ, Weinberg MH, Adetayo OA. An algorithmic approach to the management of infantile digital fibromatosis: review of literature and a case report. Eplasty. 2018;18:e19.
4. Plusjé LG, Bastiaens M, Chang A, Hogendoorn PC. Infantile-type digital fibromatosis tumour in an adult. Br J Dermatol. 2000;143(5):1107-1108.
5. Laskin WB, Miettinen M, Fetsch JF. Infantile digital fibroma/fibromatosis: a clinicopathologic and immunohistochemical study of 69 tumors from 57 patients with long-term follow-up. Am J Surg Pathol. 2009;33(1):1-13.
6. Niamba P, Léauté-Labrèze C, Boralevi F, et al. Further documentation of spontaneous regression of infantile digital fibromatosis. Pediatr Dermatol. 2007;24(3):280-284.
7. Marks E, Ewart M. Infantile digital fibroma: a rare fibromatosis. Arch Pathol Lab Med. 2016;140(10):1153-1156.
8. Ward PE, McCarthy DJ. Periungual fibroma. Cutis. 1990;46(2):118-124.
9. Boffeli TJ, Abben KW. Acral fibrokeratoma of the foot treated with excision and trap door flap closure: a case report. J Foot Ankle Surg. 2014;53(4):449-452.