Differential diagnosis of fibromatosis and fibrosarcoma with histopathologic characteristics and IHC markers

Background: Fibromatosis includes a variety of fibroblastic proliferation whose biological trend and histopathological patterns are at intermediate level between benign fibroblastic lesions and fibrosarcoma. Accordingly, because of overlapping of histopathologic features of fibrosarcoma, particularly low-grade type, with fibromatosis, the present study was conducted to find more precise criteria for histopathological and immunohistochemical (IHC) differentiation of these lesions. Methods: In this cross-sectional descriptive analytical study, a total of 40 specimens from pathology department archives in hospitals of Isfahan and Tehran universities from 2003 to 2013, including 20 fibrosarcoma and 20 fibromatosis biopsies, were selected. First, histopathologic characteristics were identified using H&E slides and an optical microscope H&E slides and then they were stained through immunohistochemical staining technique using the EnVision for markers Ki-67 and β-catenin. Afterward the samples were examined by optical microscope and positively stained cells were counted. Results: There was no significant difference between fibromatosis and fibrosarcoma in terms of a mean age (P=0.063), distribution of gender frequency (P=0.197), necrotic rate (P=0.602), clarity of nucleolus (P=0.799) and SID mean of β-catenin marker (0.369). However, it was seen a meaningful difference between fibromatosis and fibrosarcoma in terms of frequency distribution (P=0.017), rate of mitotic figures (P<0.001), rate of herring-bone pattern (P=0.043), rate of cellularity (P<0.001), rate of nucleus overlapping (P<0.001), mean of Ki-67 (P=0.046), mean of Ki-67-limit (P=0.001) and atypia rate (P