Deep fibromatosis (desmoid tumor): Cytopathologic characteristics, clinicoradiologic features, and immunohistochemical findings on fine-needle aspiration

BACKGROUND. Deep fibromatosis or desmoid tumor (DF/DT) is a low-grade, soft tissue lesion that is notable for its infiltration and local recurrence and its inability to metastasize. Although the histologic features of DF/DT are well described, there is a paucity of literature regarding cytologic findings. METHODS. The surgical pathology files of The Johns Hopkins Hospital revealed 17 patients with a diagnosis of DF/DT with prior cytology in a 16-year period (1989-2005). The clinicoradiologic findings were noted, and the fine-needle aspiration (FNA) slides were available for review in 8 patients. In patients with archived tissue, an immunohistochemical panel was performed that included β-catenin, desmin, CD-34, and c-kit. RESULTS. There was a wide age range and a wide range of anatomic distribution for DF/DT in this series. Eleven patients (65%) had a prior history of surgery at or near the site of DF/DT. Radiologically, 5 of 11 patients (45%) who had in-house studies available and no history of DF/DT were diagnosed as suspicious for malignancy. Predominantly bland spindled cells with long, fusiform nuclei and metachromatic matrix material were present in most tumors. The tumor cells were present both singly and as fragments embedded in the matrix. Nine patients had paraffin-embedded tissue samples available for immunohistochemical staining. Six of those samples demonstrated nuclear β-catenin reactivity, and all 9 samples were negative for desmin, CD-34, and c-kit. CONCLUSIONS. The current results indicated that clinical history in patients with suspected DF/DT is important. Because of the infiltrative nature of DF/DT, the radiographic impression often is over-called as suspicious for malignancy. The cytomorphology is nonspecific, often resulting in descriptive diagnoses. Immunohistochemical stains increase the yield of FNA.