was first described by Stout in 1954 as 'congenital generalized fibromatosis' and was renamed as infantile myofibromatosis by Chung and Enzinger
after recognition of the myofibroblastic
nature of the lesion.
(1) Solitary myofibromatosis:
the presence of one nodule in the skin, muscle, bone or subcutaneous
(2) Multicentric type which
can be divided into two sub-types :
(2a) Multicentric lesions
but without visceral involvement. (2b) Visceral involvement is present.
The term myopericytoma
was first proposed in 1996 by Requena as an alternative designation for 'solitary myofibroma' .
It was later adopted in 1998 to describe a spectrum
of tumours with striking concentric perivascular proliferation of spindle
(perivascular myoid cells).
[This spectrum includes - infantile-type
myofibromatosis ; solitary myofibroma ; benign myopericytoma; infantile
hemangiopericytoma ; glomangiopericytoma]
Infantile Myofibromatosis is the most common fibrous tumour of
infancy and must be considered when evaluating children who present with
either solitary or multiple tumours, particularly during the neonatal
skin, subcutaneous tissue and skeletal muscle are
affected most frequently, usually in the head, neck and trunk.
most frequently affected bones are the skull, vertebrae, ribs, femur and
Solitary lesions involving the viscera are rare.
Solitary or multicentric lesions confined to skin, soft tissues or bone
has a good prognosis.
These are usually cured by simple excision.
In the generalized form,
the most common locations are the lung, heart, gastrointestinal tract and
pancreas, as well as rarely the central nervous system.
Infants with generalized
visceral lesions have the worst prognosis.
Death in these cases often occurs due to cardio-pulmonary or
Solitary Myofibroma - Adult lesions are often solitary and
superficial in nature.
The tumour usually presents as a cutaneous
nodule in head and neck region.
Visceral and osseous lesions have not been reported.
The lesion may present as a firm scar or a superficially located well
circumscribed but uncapsulated nodule.
The deeper lesions are
more infiltrative and diffuse in nature.
nodule has a central and peripheral area.
The peripheral area consists of spindle cells (myofibroblasts)
with eosinophilic cytoplasm and ovoid nuclei arranged in well-demarcated
short bundles and fascicles resembling smooth muscle.
The central portion
consists of less differentiated rounder cells with pale cytoplasm and
basophilic, small round nuclei, arranged in a hemangiopericytoma-like
Hemangiopericytomatous and myofibroblastic
components occur in variable proportions.
More primitive areas show necrosis. Focal
areas of calcification may be present.
Mild to moderate nuclear pleomorphism can
be found in most lesions.
Normal mitotic figures may be quite common.
Abnormal mitotic figures are usually not present.
Vascular invasion (subendothelial
proliferation of perivascular spindle cells) is common, but does not affect the prognosis.
Cells are vimentin and alpha-smooth muscle
actin - Positive. Desmin- shows inconstant expression. S100 protein, epithelial membrane antigen
and cytokeratin - Negative
fasciitis ; Neurofibroma
Juvenile hyaline fibromatosis ; fibroma of tendon sheath ;
Infantile hemangiopericytoma versus
infantile myofibromatosis. Study of a series suggesting a continuous
spectrum of infantile myofibroblastic lesions.
Inflammatory myofibroblastic tumour ;
Low grade myofibrosarcoma ;
Sections from the central cellular portion
may show features mimicking small round cell sarcomas with a
hemangiopericytoma-like vasculature: Example-
poorly differentiated synovial sarcoma.