Dumbbell Spinal Desmoid Tumor Mimicking a Giant Schwannoma: Case Report and Literature Review

Background/Objectives: Desmoid tumors (DTs) are rare benign soft tissue neoplasms characterized by local aggressiveness and high rate of recurrence. Spinal localization is only anecdotally reported in the literature. When presenting in a dumbbell-shaped configuration, they can mimic neurogenic tumors. Methods: We report a rare case of a spinal intracanalar–intrathoracic DT, initially suspected to be a schwannoma, and review the literature. Results: A 24-year-old asymptomatic man was incidentally found to have a mediastinal mass on chest X-ray. CT and MRI revealed a left thoracic paravertebral mass (T9–T12), with intracanalar extension through the T10–T11 foramen, suggestive of a dumbbell-shaped neurogenic tumor. After embolization, the patient underwent surgery via a posterior combined intracanalar and endothoracic approach. Histology and immunohistochemistry analysis identified the tumor as a desmoid type fibromatosis (β catenin positive; S100, CD34, SMA negative). Follow-up MRI at 8, 12, and 18 months showed stable residual intrathoracic mass. Conclusions: To date, only 36 cases of spinal DTs have been reported in the literature, of which only 6 exhibited dumbbell morphology. Immunohistochemical and molecular pathological testing is essential for diagnosis. Although wide resection is preferred, anatomical limitations often necessitate marginal or subtotal surgery, which increases the risk of recurrence (24–77%). Our review showed a 29% overall recurrence rate (50% after subtotal, 29% marginal, 20% wide resection). Adjuvant radiotherapy or systemic therapies may help improve outcomes. Spinal DTs pose significant diagnostic and therapeutic challenges. In the absence of established guidelines, management should be individualized and multidisciplinary. Lifelong follow-up is essential due to the high risk of recurrence.