OBJECTIVETo study the clinicopathologic features and histogenesis of calcifying fibrous tumor (CFT).

METHODSThe clinical manifestations, histopathologic characteristics and immunophenotype were analyzed in 11 cases of CFT.

RESULTSThe male-to-female ratio was 5:6, with a mean age of 38 years and age range of 25 to 52 years. The sites of involvement included abdominopelvic cavity (n=6), soft tissue (n=4) and scrotum (n=1). Most patients presented with a gradually enlarging and painless mass. Nearly half of the cases were associated with other diseases or history of inflammation, trauma or surgical intervention. One third of the tumors represented incidental findings and showed no recurrence after resection. Imaging revealed a solitary solid soft tissue mass or multiple nodules with clear borders and associated high-density calcifications. Macroscopically, the tumors were well-circumscribed but non-encapsulated. They ranged from 0.5 to 20.0 cm in diameter and were tan-greyish, round to oval, lobulated or irregular and solid with rubbery consistency. The cut surface was whitish to tan-yellowish, gritty and showed scattered spotty yellowish discoloration corresponding to the foci of dystrophic calcifications. Histologically, CFT was composed of hyalinized fibrous tissue and thickened vessel walls with interspersed bland spindly fibroblastic cells, scattered psammomatous calcifications, dystrophic calcification and lymphoplasmacytic infiltration. In addition, focal cloak-like polymorph infiltration at the tumor periphery and entrapment of adipocytes and nerves were demonstrated in some cases. Foci resembling solitary fibrous tumor, fibromatosis, keloid or inflammatory myofibroblastic tumor were observed. Immunohistochemical study showed that the tumor cells were diffusely positive for vimentin and focally positive for CD34, factor VIII-related antigen and beta-catenin. The admixed plasma cells were notably IgG positive, with more than 50% being IgG4 positive.

CONCLUSIONSCFT has characteristic histopathologic manifestations and shows morphologic and immunohistochemical overlaps with known IgG4-related sclerosing diseases. It is possible that CFT may represent another example of IgG4-related diseases. It often runs a benign clinical course, with rare recurrence after surgical resection. Previous inflammation and trauma may be the precipitating factors of CFT.