Clinicopathological findings in a case series of extrathoracic solitary fibrous tumors of soft tissues

Abstract

Background: Solitary fibrous tumors (SFT) represent a rare entity of soft tissue tumors. Previously considered being of serosal origin and solely limited to the pleural cavity the tumor has been described in other locations, most particularly the head and neck. Extrathoracic SFT in the soft tissues of the trunk and the extremities are very rare. Nine cases of this rare tumor entity are described in the course of this article with respect to clinicopathological data, follow-up and treatment results.

Methods: Data were obtained from patients' records, phone calls to the patients' general practitioners, and clinical follow-up examination, including chest X-ray, abdominal ultrasound, and MRI or computed tomography.

Results: There were 6 females and 3 males, whose age at time of diagnosis ranged from 32 to 92 years (mean: 62.2 years). The documented tumors' size was 4.5 to 10 cm (mean: 7 cm). All tumors were located in deep soft tissues, 3 of them epifascial, 2 subfascial, 4 intramuscular. Four tumors were found at the extremities, one each at the flank, in the neck, at the shoulder, in the gluteal region, and in the deep groin. Two out of 9 cases were diagnosed as atypical or malignant variant of ESFT. Complete resection was performed in all cases. Follow-up time ranged from 1 to 71 months. One of the above.mentioned patients with atypical ESFT suffered from local relapse and metastatic disease; the remaining 8 patients were free of disease.

Conclusion: ESFT usually behave as benign soft tissue tumors, although malignant variants with more aggressive local behaviour (local relapse) and metastasis may occur. The risk of local recurrence and metastasis correlates to tumor size and histological status of surgical resection margins and may reach up to 10% even in so-called "benign" tumors. Tumor specimens should be evaluated by experienced soft tissue pathologists. The treatment of choice is complete resection followed by extended follow-up surveillance.

Figure 1

clinical aspect of SFT. Clinical aspect of a solitary fibrous tumor of the lower left leg: swelling with soft tissue mass (same patient as in fig. 3).

Figure 2

MRI of SFT. MRI of a solitary fibrous tumor depicting a relatively well circumscribed soft tissue tumor in the forearm.

Figure 3

Macroscopic aspect of SFT. Macroscopic aspect of a solitary fibrous tumor: cut surface of a well circumscribed tumor; white to tan coloured cut surface with some deeply yellow necrotic areas (atypical/malignant solitary fibrous tumor, case 8).

Figure 4

Microscopic aspect of SFT (a). Microscopic aspect of a solitary fibrous tumor: "Patternless" growth pattern with cellular (right half) and some myxoid (left half) areas, hemangiopericytoma-like wide blood vessels.

Figure 5

Microscopic aspect of SFT (b). Microscopic aspect of a solitary fibrous tumor, higher magnification: fibroblastic, partly "neural-like" tumor cells lying in a fibrous, partly hyalinized matrix, hemangiopericytoma-like blood vessels.