cells that blend a variable set of features seen in fibroblasts, the most common cell type in connective tissue, with a variable set of features seen in smooth muscle cells.Treatment of IMF tumors depends upon the tumor numbers, locations, and genetic abnormalities found in each individual and often include more than one therapeutic regimen. Individuals with solitary tumors are usually treated by observation with the expectation that many of these tumors will regress spontaneiously. Single tumors located in vital areas (e.g. intracranial tumors) and tumors that do not regress over suitable observation periods are often treated by surgical removal. Multiple tumors (with viscera involvement) and surgically inaccessible life-threatening IMF tumors have been treated with one or a combination of chemotherapy drugs, radiation therapy or, in tumors with certain PDGFRB gene mutations, drugs directed specifically against this mutated genes protein product. Presentation
IMF tumors are usually painless, well-encapsulated, rubbery to hard, and freely movable-to-fixed masses. They may be evident at birth in up to 60% of cases but generally go undetected until they are diagnosed in the first year of life, uncommonly in older infants and young (<10 years/old) children, or rarely in older children and adults (one individual was diagnosed with IMF at 85 years of age). The tumors may be flesh-colored papules or nodules; plaques (i.e. flat-topped papules that are equal to or greater than 10 mm in largest diameter); pedunculated, calcified masses; or ulcerated, necrotic masses. Most of these tumors are <1 cm in diameter but can be much larger, e.g. 5.2 cm in diameter.
Multiple tumors (no viscera involvement)
Multiple tumors (no viscera involvement) typically occur as dozens to hundreds of mostly small tumors located in various areas such as the skin, muscles, and frontal eye socket, These tumors do not involve visceral organs, often take a benign course, and may regress spontaneously. Multiple tumors (with viscera involvement)
Multiple tumors (with viscera involvement) typically occur as dozens to hundreds of tumors located in the same sites as multiple tumors (no viscera involvement) but also occur in one or more visceral organs such as those in the gastrointestinal tract and upper respiratory tract and/or the heart, liver, cerebellum, rectum, parietal cortex of brain, and lung. This form of IMF, particularly in cases with tumors involving the gastrointestinal tract, heart, and/or lung, has a far higher morbidity and mortality than the other forms with death occurring in infants during the first weeks to 4 months of life in 30–70% of cases Death is typically due to a tumors compression of vital organs or tissues (e.g. blood vessels). However, there are uncommon cases of multiple tumors (with viscera involvement) that were not associated with serious symptoms, were observed without treatment, and over time showed spontaneous regressions of all or almost all of their tumors. Pathology
Microscopic histopathologic analyses of IMF tumor tissues commonly show repeated patterns of a central zone consisting of spindle-shaped cells lining capillaries and round-to-oval cells arranged around prominent "antler-shaped" vascular spaces all of which are surrounded by a peripheral zone of clustered smooth muscle-like cells.