infantile myofibroma

Digital case

 Case 205 (HPC:205) : Infantile myofibroma

Epidemiology

 sporadic cases
 familial cases (8600777)

• autosomal dominant inheritance (12894106, 1739928, 6742314)
• autosomal-recessive inheritance (11260217)

Localization of tumors

 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

Microscopical synopsis

Biphasic pattern
 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)

Immunochemistry

 vimentin+
 smooth muscle actin+

Subtypes

 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

Associations (sporadic)

 neonatal hemochromatosis (11196755)
 Turner syndrome (9821432)
 arterial fibromuscular dysplasia (15455480)

Cytogenetics

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

Prognosis

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

• low-grade myofibroblastic sarcoma (9777985)

 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

• schwannoma and neurofibroma
• low-grade MPNST

 juvenile xanthogranuloma

See also

 hemaniopericytomatous pattern

References

 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