Desmoplastic fibroma of the scapula with fluorodeoxyglucose uptake on positron emission tomography: a case report and literature review

We present a case of desmoplastic fibroma (DF) arising from the right scapula that was incidentally identified by fluorodeoxyglucose-positron emission tomography (FDG-PET) imaging performed to evaluate the presence of metastasis due to a history of surgical treatment for endometrioid adenocarcinoma. A 65-year-old woman was admitted to our hospital for consultation about a bone lesion in the right scapula although she was asymptomatic. FDG-PET revealed moderate focal (18)F-FDG uptake in the right scapula with a maximal standardized uptake value of 3.2. The lower angle of the scapula was unclear on plain radiology. Needle biopsy was performed to make a differential diagnosis between primary bone and metastatic tumor. Pathologically, the tumor was composed of a relatively sparse proliferation of spindle-shaped fibroblastic/myofibroblastic cells in a dense collagenous background. Therefore, the diagnosis was a primary fibrous bone tumor. Wide excision was performed, because of the possibility of malignant tumors such as low-grade fibrosarcoma in light of the FDG-PET uptake. Pathologically, the resected tumor was composed of a proliferation of less atypical spindle cells in the collagenous stroma with focally myxoid change; no mitotic figures were observed. Immunohistochemically, β-catenin nuclear/cytoplasmic staining was not observed, and no β-catenin genetic mutations were detected. Therefore, the tumor was diagnosed as DF. DF is a tumor that exhibits FDG-PET uptake. There were no signs of recurrence 6 months after surgery.