Diagnosis
Based on their clinical presentation and gross appearance IMF tumors can be confused with a wide range of benign and malignant papular, nodular, and tumorous lesions particular in cases which involve multiple tumors. However, the presence of two zone histopathology, family history of disease, and presence of the above cited PDGFRB gene mutations are almost always definitive indicators of IMF. IMF and the classic form of mesoblastic nephroma have been suggested to be the same disease because of their very similar histopathology. However, mesoblastic nephroma tumor cells, unlike IMF tumor cells, express cyclin D1 and Beta-catenin proteins and therefore likely have a very different cellular origin than IMF tumors. Infantile digital fibromatosis, a tumor that develops primarily in the fingers and toes, had been regarded as a type of IMF. However its tumors have a distinctly different clinical presentation and histopathology than IMF. The World Health Organization (2020) redefined infantile digital fibromatosis as a benign tumor in the in the category of benign fibroblastic and myofibroblastic tumors and therefore different than IMF. Treatment and prognosis
There are no controlled studies to define the optimal treatment(s) for IMF. The following give the currently widely used and recommended treatments along with the result of these treatments for the three categories of the IMF tumors. Solitary IMF tumors
Solitary IMF tumors typically grow slowly, produce few or no symptoms, and often regress spontaneously within 18 to 24 months of diagnosis. A watchful waiting strategy is commonly used for these tumors.
At least 9 IMF cases described in the English literature were diagnosed in fetuses based on the findings of fetal spectrogram and/or magnetic resonance imaging. IMF tumors in the viscera or deep tissues may present with serious or life-threatening signs and symptoms of organ and/or deep tissue damage due to these tumors space-filling and pressuring effects.Some individuals with IMF present with a family history of IMF tumors. To date (2021), 20 families have been reported to carry various germline (i.e. inherited) mutations in one of their two PDGFRB genes. All of these mutations were gain of function mutations (i.e. the mutant genes product is overactive) and inherited in an autosomal dominant manner with incomplete penetrance. Among 36 identified familial carriers of these mutant genes, 4 had no history of IMF, 3 had developed a solitary IMF, 29 had developed multiple tumors (no viscera involvement) or multiple tumors (with viscera involvement) IMF, and 2 had died. Most of these individuals were diagnosed with IMF in their infancy or early childhood. Subsequent studies have found that up to 70% of individuals with IMF and no family history of the disease also carry mutations in one of their two PDGFRB genes in the cells of their tumor tissues. These mutations are somatic mutations (i.e. non-inherited mutations developing only after conception) that are identical or similar to those seen in familial cases. The familial and non-familial mutated PDGFRB genes produce highly overactive platelet-derived growth factor receptor beta (i.e.