ABSTRACT
Objective@#To study the incidence and clinicopathological features of intermediate fibroblastic/myofibroblastic tumors(IF/MFT) in infants and the young children.@*Methods@#All available cases with soft tissue tumors in infants and children were retrieved from the files of Women and Children′s Hospital Affiliated to Qingdao University, from January 2012 to December 2017.The incidence rate of IF/MFT was observed.Cases of IF/MFT were identified and investigated by light microscopy and immunohistochemistry by reviewing the related literature.@*Results@#Among 290 soft tissue tumors, 15 cases(5.2%) were IF/MFT, accounted for 88.2%(15/17 cases) of borderline soft tissue tumors.Twelve cases were male, 3 cases were female, the median age was 8 months, and 4 cases were congenital.Clinically, 11 cases were presented with slow-growing painless masses located in the trunk or extremities.According to histopathology, 9 cases(60.0%) were categorized as infantile fibromatosis(IFM), including 5 cases(33.3%) desmoid-type and 4 cases(26.7%) diffuse-type; 3 cases(20.0%) as lipofibromatosis(LFM); 2 cases(13.3%) as infantile fibrosarcoma(IFS) and 1 case(6.7%) as giant cell fibroblastoma(GCF). All 15 tumors were characterized by the presence of spindle fibroblasts and myofibroblasts with infiltration of the surrounding structures.Immunohistochemically, all the 15 cases were diffusely positive for Vimentin(Vim), but negative for Myogenin, MyoD1, Desmin and S-100.Smooth muscle actin(SMA), β-catenin and Bcl-2 were positive in some cases to a certain degree.The Ki-67 proliferation index was higher in diffuse-type IFM and IFS, the former was 5.0%-20.0%, and the latter was about 20.0%, however, the other cases showed Ki-67 <5.0%.The main clinical treatment was complete or extensive excision.@*Conclusions@#IF/MFT accounts for a high proportion of intermediate soft tissue tumors in infants and young children, mostly seen in male children, and IFM and LFM are the main types.The clinical signs and symptoms associated with these tumors are often nonspecific, and their histopathologic manifestations may overlap.The final diagnosis of IF/MFT must depend on the characteristics of age, location, histopathologic changes and immunohistoche-mical findings.