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infantile myofibromatosis

Thursday 9 February 2006

Definition: Infantile myofibromatosisis is defined by the presence of multiple infantile myofibromas. Infantile myofibromatosis is a term coined by Chung and Enzinger.

It exclusively affects infants and young children, with 60% of cases noted at birth or shortly thereafter and more than 80% occurring before the age of 2 years.

Infantile myofibromatosis is one of the most commonly occurring tumors of the neonatal period, presenting in both solitary and multicentric forms.

Most solitary forms occur in the head and neck region; the upper extremity is the next most common site. Solitary lesions are usually cutaneous, involving the dermis and extending to subcutaneous tissue, muscle, and bone.

The visceral type is associated with significant morbidity, sometimes even mortality, and its presence requires clinical evaluation for other potential multicentric tumors.

Spontaneous regression is generally the natural history of those infantile myofibromatosis lesions without visceral involvement.

A histologic zoning phenomenon is present in infantile myofibromatosis lesions. Peripheral spindle-shaped cells arranged in bundles blend centrally into less differentiated round or polygonal cells arranged in sheets.

The spindle cells have the ultrastructural and immunohistochemical characteristics of myofibroblasts, staining positive for vimentin and alpha-smooth-muscle actin but negative for desmin.

The cells are also negative for s-100 protein, differentiating them from more immature histiocytes. Progressive cell differentiation is a possible explanation for the spontaneous regression of the solitary lesions.


- sporadic cases
- familial cases (8600777, 16581573)


- orbital region (11410140)
- central nervous system (12720031), spinal canal (9703012)
- oral region (10792791), gingiva (12472999)
- bone
- muscle
- viscera (heart, lungs, liver, gastrointestinal tract (2672792), bile ducts and pancreas (3185365), endocrine organs)
- subcutaneous tissue, soft tissues
- digestive tract

  • intestinal infantile myofibromatosis

- infantile generalized myofibromatosis

Microscopical synopsis

Biphasic pattern
- zonation effect : smooth-muscle-appearing cells on the periphery of the lesion with central fibromatosis cells
- fascicles of spindle cells with abundant eosinophilic cytoplasm that resembled smooth muscle
- more primitive spindled cells associated with a hemangiopericytoma-like vascular pattern
- interlacing fascicles of myofibroblasts with abundant eosinophilic cytoplasm
- variable necrosis
-  calcifications in some sites
- hemangiopericytoma-like features
- angiocentric and perivascular growth of myofibroblasts (+/-) (8597844)


- vimentin+
- smooth muscle actin+


- solitary myofibromatosis
- systemic myofibromatosis, multicentric myofibromatosis

  • congenital generalized myofibromatosis (CGMF) (8597844)
  • aggressive infantile myofibromatosis (3784986)

Two types can be distinguished; the solitary type, defined by the presence of one nodule in the skin, muscle, bone or subcutaneous tissue; and the multicentric type which can be divided into two sub-types.

In the first sub-type the lesions are multicentric but without visceral involvement, while in the second, visceral involvement is present.

- adult-type myofibroma
- infantile generalized myofibromatosis

Associations (sporadic)

- neonatal hemochromatosis (11196755)
- Turner syndrome (9821432)
- arterial fibromuscular dysplasia (15455480)
- verrucous epidermal nevus (15459537)
- neurofibromatosis type 1 (NF1) (15459537)
- multiple congenital anomalies (2303073, 15916589)


- del(6)(q12q15) (10425309)
- monosomy 9q (15365831)
- trisomy 16q (15365831)


The prognosis of the disease depends on whether visceral involvement is present. Solitary and multicentric nodules without visceral involvement usually have excellent prognosis with spontaneous regression of lesions within 1 to 2 years of diagnosis.

Visceral lesions are associated with a significant morbidity and mortality, resulting from vital organ obstruction, failure to thrive, or infection. Death in these cases often occurs at birth, or soon after, and is usually due to cardio-pulmonary or gastrointestinal complications. However, multicentic type of infantile myofibromatosis with visceral involvement can spontaneously regress. (11510506)

Differential diagnosis

- low-grade myofibroblastic neoplasms

- fibromatoses

  • composite fibromatoses

- congenital fibrosarcoma (infantile fibrosarcoma)
- inflammatory myofibroblastic tumor
- fibrous fibrohistiocytic tumors
- solitary fibrous tumor
- nodular fasciitis
- desmoplastic fibroblastoma (collagenous fibroma)
- smooth muscle tumors

  • leiomyoma
  • leiomyosarcoma

- neurogenic tumors

- juvenile xanthogranuloma

See also

- hemaniopericytomatous pattern
- fibrosing tumors (sclerosing tumors)
- fibrous tumors
- myofibroblastic tumors
- fibroblastic/myofibroblastic tumors


- Granter SR, Badizadegan K, Fletcher CD. Myofibromatosis in adults, glomangiopericytoma, and myopericytoma: a spectrum of tumors showing perivascular myoid differentiation. Am J Surg Pathol. 1998 May;22(5):513-25. PMID: 9591720

- Mentzel T, Calonje E, Nascimento AG, Fletcher CD. Infantile hemangiopericytoma versus infantile myofibromatosis. Study of a series suggesting a continuous spectrum of infantile myofibroblastic lesions. Am J Surg Pathol. 1994 Sep;18(9):922-30. PMID: 8067513

- Dictor M, Elner A, Andersson T, Ferno M. Myofibromatosis-like hemangiopericytoma metastasizing as differentiated vascular smooth-muscle and myosarcoma. Myopericytes as a subset of "myofibroblasts". Am J Surg Pathol. 1992 Dec;16(12):1239-47. PMID: 1463097