Background Desmoid tumors have a tendency to recur locally, and traditionally they have been treated surgically. No treatment is sometimes indicated, however; this requires a morphological diagnosis that is not based on a surgical specimen. In this study we aimed to identify the diagnostic accuracy of needle and core biopsy for the morphological diagnosis of desmoid.Methods We compared the diagnostic accuracy of fine-needle aspiration (FNA) and core needle biopsy (CNB) in 69 and 26 patients, respectively, who had had surgical resections for desmoid. We also reviewed 15 additional cases that had been incorrectly diagnosed as desmoid on FNA but which had different diagnoses after surgery.Results FNA-based diagnoses of desmoid/fibromatosis were rendered in 35 of 69 cases, and other benign spindle cell proliferations in 26 cases and spindle cell sarcoma in the remaining 4 cases. All 26 CNBs were either suggested to correspond to desmoid (24) or other benign spindle cell lesions (2). Of the 15 FNAs incorrectly diagnosed as desmoid, 2 were found to be sarcomas.Interpretation FNA is fairly reliable for recognition of the benign nature of desmoids. Occasional over-and under-diagnosis of malignancy can occur, however. CNB appears to be more reliable.

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Background Until now, surgical treatment has been the mainstay in the treatment of desmoid tumors, even though it is associated with a high recurrence rate. There have, however, been occasional case reports showing that desmoid tumors may spontaneously decrease in size or even disappear.Patients and methods This is a retrospective review of 8 patients with abdominal (5) or extra-abdominal (3) desmoid tumors who were followed both clinically and with imaging techniques (sonography, CT or MRI). Mean follow-up time was 4.4 (0.8-7.5) years. Tumor volume was assessed in each investigation and followed over time.Results 3 tumors disappeared, 2 diminished in size, 1 did not change and 2 tumors became larger, 1 of which had trippled in volume at the latest follow-up.Interpretation Desmoid tumors have probably been overtreated in the past. Many of them tend to regress spontaneously.