Congenital Myofibroma Mimicking an Infantile Hemangioma in an Infant

Sir,

An 11-month-old boy presented to the pediatric dermatology clinic for evaluation of a suspected infantile hemangioma (IH) on his back. According to her mother, this lesion was present at birth, but had increased in size. There was no any prior treatment. Patient was an otherwise well neonate, having been a product of an unremarkable pregnancy and full term delivery. Physical examination revealed a solitary 1-cm sized firm erythematous irregular nodule on his back [Figure 1a]. Histopathological examination of the biopsy revealed that the tumor was circumscribed, but not encapsulated. It was composed largely of spindle cells with oval vesicular nuclei and eosinophilic cytoplasm Some areas demonstrated more rounded cells. Mitotic figures were scarce. The perivascular spindle cell proliferation was more pronounced at the periphery of the tumor. The central portion of the mass was largely fibrotic, with residual vascularity in some fibrotic areas [Figure 1b and c]. Patient was referred to plastic and reconstructive surgery for a complete excision. The mass was removed enbloc along with several millimeters of surrounding normal skin and subcutaneous tissue.

Figure 1.

(a) A solitary 1-cm sized firm erythematous irregular nodule on the back. (b) Encapsulated and large nodular lesion composed of soild aggregates of plump spindle-shaped cells in fascicles in dermis. Spindle cell proliferation was more pronounced at the periphery of the tumor. The central portion of the mass was largely fibrotic with collagen degeneration (H and E, ×40). (c) The periphery of the myofibroma shows round fascicles with blue mucin deposition (H and E, ×100)

Infantile myofibroma (IM) is an extremely rare fibrous tumor of infancy composed of a benign proliferation of fibroblasts and myofibroblasts. The most common form of IM is the solitary type, which manifests as an isolated tumor involving the dermis and subcutis and is present at birth in 50% to 60% of cases,[1,2,3,4] but multicentric forms also exist, wherein multiple tumors may arise in skin, skeletal muscle, bone and viscera.[1,2,3,4] Clinically, the solitary IM almost invariably presents as a painless, firm, occasionally bluish, cutaneous or subcutaneous nodule. Solitary IMs are most commonly found on the head and neck, with the trunk and extremities less often affected.[1,2,4] Lesions confined to skin and bones tend to regress spontaneously without much clinical significance;[1,2,3,4] visceral involvement carries a much less favorable prognosis, with death reported in 75% of cases soon after birth.[2,4]

IM has previously been recognized as an entity that may masquerade as IH.[5] In our case, the anatomic location and much higher frequency of IH in the neonatal population made IH the suspected diagnosis, but as Frieden et al.[5] suggested, the congenital nature of the lesion and the presence of scarring and skin contracture are clinical clues suggestive of something other than IH. IH typically appear between 1 and 4 weeks of age and demonstrates rapid growth over a few months, with involution occurring over several years. Clinicians should have a low threshold to biopsy soft-tissue lesions that deviate from this classic presentation. It is crucial to exclude other processes such as IM, fibrosarcoma, rhabdomyosarcoma and kaposiform hemangioendothelioma, which have different treatments and prognosis.[1,2,3,4,5]