<unk> F 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<unk> F 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. At least 9<unk> F cases described in the English literature were diagnosed in fetuses based on the findings of fetal spectrogram and/or magnetic resonance<unk> aging.<unk> F 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<unk> F present with a family history of<unk> F 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 gene's 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<unk> F, 3 had developed a solitary<unk> F, 29 had developed multiple tumors (no viscera involvement) or multiple tumors (with viscera involvement)<unk> F, and 2 had died. Most of these individuals were diagnosed with<unk> F in their infancy or early childhood. Subsequent studies have found that up to 70% of individuals with<unk> F 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. PDGFβ receptor} proteins that contribute to the development and/or progression of<unk> F. A mutation in one of the two NOTCH3 genes has been reported to occur in a single family with autosomal dominant inheritance of<unk> F: 9 of this family's members had<unk> F plus the mutation while 7 of its members did not have<unk> F or the mutation. Since the mutated NOTCH3 gene in this family produces an overactive neurogenic locus notch homolog protein 3 product that in cell culture studies increases the expression of the PDGFRB gene's product, the PDGFβ receptor, this NOTCH3 mutation may promote the development and/or progression of<unk> F in a manner similar to PDGFRB mutant genes, i.e. by increasing the number and therefore overall activity of the PDGFβ receptor. Further studies are needed to define NOTCH3 gene mutation's frequency of occurrence in, and contribution to the development of,<unk> F. Solitary<unk> F tumors Solitary<unk> F tumors represent 50 to 74% of all<unk> F cases. These tumors commonly present with a mass that infiltrates the surrounding tissue in the head and neck areas (e.g. in the ethmoid sinus/maxillary sinus, infratemporal fossa, tongue, hard palate, behind an ear, or temporal bone); less commonly in other sites such as the scapula/axilla area, lower back, or soft tissue/bone in the lower leg; and also less commonly in visceral organs such as the pancreas, spleen, lung, or heart. Solitary<unk> F tumors often (i.e. 25 to 61% of cases in different studies) regress spontaneously. 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<unk> F, 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 tumor's 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.
Infantile myofibromatosis
Acrokeratoelastoidosis of Costa
Metachondromatosis
Familial myxovascular fibromas
Enchondromatosis
Phakomatosis
Juvenile hyaline fibromatosis
Cardiac fibroma