Aspiration biopsy cytology of extraabdominal desmoid tumor concurrently occurring in a patient with tumoral calcinosis.

Extraabdominal fibromatosis or desmoid tumor (DT) is a slow growing locally aggressive soft tissue tumor that can occur anywhere in the body. We report the aspiration biopsy cytology features of a case of DT of the right neck area in a 35-year-old man who had a long standing history of tumoral calcinosis. The aspirate was interpreted as "benign spindle cell lesion" and confirmed as DT on histologic examination of the resected mass. We discuss the possible differential diagnoses of other benign or malignant lesions on fine-needle aspiration (FNA) biopsy and especially discuss the aspiration cytology features of DT compared with those of tumoral calcinosis. We also discuss the value of immunohistochemical markers that help in differentiating DT from other entities.