Background: Desmoid type fibromatoses has proven to be a diagnostic and therapeutic challenge, as they often appear primarily as a carcinoma of the breast with a high recurrence risk.

Patients: A digital archive search was performed for the period from 2009 to the end of 2018. Inclusion criteria consisted of histological examination of at least the surgical specimen in the reference pathology department and at least a second opinion diagnosis in the reference radiology department.

Results: A total of 14 women and 1 man underwent surgery on desmoid type fibromatosis of the breast. The average patient age was 49 years (range: 22-72 years). The mean tumor size was 2.2 cm (range: 0.8-4.2 cm). The tumor was detectable in mammography in 12 out of 13 patients and in all 15 patients in sonography. MRI was performed preoperatively in 6 patients; in all of the patients, the tumor was visualized with inhomogeneous contrast enhancement. In the imaging procedures, all desmoid type fibromatoses were classified as suspicious. Performing the core biopsy, preoperative histology confirmed desmoid fibromatosis in 12 out of 15 patients. Nuclear stain for ß-catenin was positive in 7 out of 10 patients. Negative staining was found for AE1/A3 in 10 out of 10 and CD34 in 12 out of 12 patients. In all of the patients, a single-stage operation without the detection of border-forming tumor margins was performed. The follow-up interval ranged from 16 to 96 months (mean: 44.86 months, median: 43 months). In this follow-up period, no patient was diagnosed with desmoid tumor recurrence.

Conclusion: In imaging, desmoid type fibromatosis of the breast has typical malignancy-related criteria. Extensive preoperative diagnostics enable the planning of complete primary excision of the lesion and reduce the recurrence risk.