Congenital Lesion on the Hand of a Child: Answer

Abstract

DISCUSSION Infantile digital fibromatosis is a benign tumor lesion of myofibroblastic origin described by Reye in 1965.1 It usually manifests congenitally or in the first 2 years of childhood, as a fungiform, cupuliform, or polypoid tumor approximately 2 cm in diameter, with a pinkor skin-colored surface, no epidermal involvement, and a firm or rubbery consistency.2 It is characteristically located on the extensor and lateral sides of the fingers and/or toes.2,3 The thumbs and big toes are not usually affected, although there are no theories justifying this finding. The lesions are usually asymptomatic, but they may cause secondary functional limitation of the joint.3 Patients with multiple metachronous or synchronous lesions have also been reported, as have atypical cases of late presentation in adults and extradigital locations.2,4 Generally, the clinical course includes an initial phase of slow growth, lasting approximately 1 month, followed by a rapidly proliferative phase of 10–14 months. The lesion finally stabilizes and tends to regress spontaneously.3 No cases of bone infiltration, malignancy, or distant metastases have been reported, although there is local recurrence of up to 60% after surgical excision.5 The histological study shows a well-delimited and nonencapsulated dermal proliferation of myofibroblastic cells grouped into a fascicular or storiform pattern, separated by collagen bundles. The epidermis is usually undamaged, although occasionally it presents hyperkeratosis, parakeratosis, flattening of the epidermal ridges and, rarely, ulceration.2,4 The tumor cells have a fusiform morphology, with a blunt, elongated nucleus, and pale eosinophilic cytoplasm. It is characteristic to find round or oval eosinophilic paranuclear inclusions, which become bright red when stained with Masson trichrome, corresponding to accumulations of fragmented actin and vimentin accumulations.2–4 The immunohistochemical study is compatible with the myofibroblastic cell origin, typically being positive for calponin, smooth muscle actin, and desmin.2,4 Transmission electron microscopy usually confirms the presence of 1–10-nm diameter, membrane-lacking, electrodense, spherical cytoplasmic accumulations, comprising clusters of fine filaments with a compact, amorphous, and finely granular core. Other less specific findings include the presence of multiple nuclear indentations or prominent golgi apparatus and endoplasmic reticulum.2 The differential diagnosis includes other fibrous acral proliferations, such as infantile fibromatosis, infantile lipofibromatosis, calcifying aponeurotic fibroma, and palmar– plantar fibromatosis.2,4,6 The presence of cytoplasmic inclusions is a specific but variable diagnostic finding. There are rare cases of infantile digital fibromatosis where inclusion bodies are absent, which have been associated with mature lesions with a higher degree of fibrosis2,7 or an intense inflammatory infiltrate.8 Considering the benign nature of the lesion, its tendency to autoinvolute, and the high rate of postoperative recurrence, a conservative stance seems recommendable in the case of stable and asymptomatic lesions.2,4 For lesions involving functional compromise, simple excision, Mohs surgery,9 intralesional 5-fluorouracil,10 and intralesional corticosteroids11 have all been described as therapeutic options, although with variable results.