Desmoid-type fibromatosis of neck masquerading as nerve sheath tumors: two case reports

Background Desmoid fibromatosis (DF) is an atypical, non-malignant tumor known for its distinctive feature of exhibiting an intermediate biological behavior that falls between benign fibrous lesions and fibrosarcoma. The article aimed to outline the imaging characteristics of desmoid fibromatosis and distinguish it from its similar counterpart, nerve sheath tumors. Results Here, we present two cases of desmoid fibromatosis whose imaging findings mimic nerve sheath tumors. The patients presented with neck swelling and radiating pain. Both cases were biopsy-proven. Imaging features characteristic of these lesions include elongated shape, split-fat sign, and fascial tail sign with mixed signal intensity on T1WIs and T2WIs depending upon the collagen content of the lesion. Conclusions MRI is the best diagnostic modality for differentiating fibromatosis from nerve sheath tumors. Surgery continues to be the primary approach for treating these growths, but in some cases, chemoradiation is employed to achieve improved control rates. The presence of intralesional low-intensity bands in T2WIs is a characteristic feature of fibromatosis. Given its local aggressiveness and propensity for recurrence, the use of multiple imaging modalities is essential for providing informed guidance on outcomes and treatment strategies.