Clinicopathologic correlates of solitary fibrous tumors

Background: Solitary fibrous tumors (SFTs) are rare fibrous neoplasms. Since their initial description as arising from the pleura, SFTs have been reported at a wide range of anatomic sites. To the authors's knowledge, there are no large series reporting both thoracic and extrathoracic SFTs nor are there any large series that analyze clinicopathologic correlates of tumor behavior.

Methods: Institutional soft tissue tumor and pathology databases were reviewed to identify patients. Pathologic material was reviewed by an experienced soft tissue pathologist and scored for the presence of a histologically malignant component. Clinical information was obtained from medical records and phone calls to patients. Statistical analysis was performed using the Student t test, Pearson chi-square test, and log-rank test.

Results: Seventy-nine patients with SFTs treated at a single institution over an 18-year period were identified. These tumors arose in a wide range of anatomic sites. Thoracic and extrathoracic SFTs had similar clinical and pathologic features, although extrathoracic tumors were more likely to be symptomatic on diagnosis. Seventy-five patients underwent surgical excision of a SFT at our institution. Overall, SFTs had a low rate of local recurrence and metastasis after surgical treatment. Extrathoracic SFTs had an increased risk of local recurrence that was small but statistically significant. There was no difference in metastasis-free survival between thoracic and extrathoracic SFTs. Positive surgical margins and the presence of a histologically malignant component were factors predicting worse local recurrence-free survival. Positive surgical margins, tumor size greater than 10 cm, and the presence of a malignant component predicted worse metastasis-free survival.

Conclusions: Solitary fibrous tumors are rare tumors that occur at all anatomic sites. Most SFT patients fare well after surgical treatment. Closer surveillance is warranted for those tumors that are larger than 10 cm or with the presence of a histologically malignant component.