Discussion
Diagnosis With Brief Discussion
- Diagnosis
- Solitary fibrous tumor of the pleura
- Radiologic Findings
- Chest X-ray PA (Fig. 1) and lateral (Fig. 2) show a well-defined pleura or extrapleural origin mass without bone destruction in the left upper hemithorax. The mass is 7.3 cm and shows heterogenous enhancement in contrast-enhanced CT with no chest wall invasion on axial (Fig. 3) and coronal (Fig.4,5) images. In MRI, the mass has T1 hypointense signal with heterogeneous enhancement, heterogeneous T2 signal, and restricted diffusion (Fig. 6,7). The mass shows mild hypermetabolism (SUVmax=1.86) on 18F-FDG PET/CT scan (Fig 8).
- Brief Review
- The tumor was resected with LUL. The tumor originated from LUL apex visceral pleura, showed no invasion to around structures, and its capsule was intact. The pathologic diagnosis was solitary fibrous tumor of the pleura, low risk (total score 2: patient age>55 (score 1), tumor size (score 1), mitosis (score 0), tumor necrosis (score 0)).
Solitary fibrous tumors (SFTs) are rare fibroblastic mesenchymal tumors. They can develop in any organ due to their spindle cell origin. The tumor is currently defined by the presence of NAB2-STAT6 gene fusions.
Most SFTs have low mitotic counts and show little nuclear pleomorphism. The presence of mitotic figures (greater than 10 per high power field), necrosis, infiltrative growth pattern, and large size is associated with aggressive (malignant) behavior. Age above 55 years is also a risk factor.
Most SFTs grow slowly and form large masses, which could be asymptomatic or cause variable compression symptoms depending on the tumor size and location. Large SFTs are associated with paraneoplastic syndromes. Secretion of insulin-like growth factor 2 by the neoplastic cells may result in refractory hypoglycemia (Doege-Potter syndrome). More rarely, IGF2 production can produce an acromegaly-like syndrome. Thoracic lesions may be associated with hypertrophic osteoarthropathy.
Local or distant recurrence of SFTs has been documented in about 10–30% of cases with 10–40% of recurrences reported after 5 years from tumor resection. Recurrence after 15 years is rare. Metastases most commonly occur in the lung, but can also be found in the liver, brain and bones.
On MRI, SFTs show hypo to isointense signal on T1-WIs, and variable signal intensity on T2-WIs. The T2 signal variability is linked to the relative amounts of mature fibrous tissue and myxoid or cystic degeneration within the tumor. Tumors with predominance of collagen and fibroblasts have low signal on T2-WIs, while degenerated lesions present high T2 signal. SFTs are highly vascular and usually show intense heterogeneous enhancement after intravenous gadolinium administration. Linear or rounded hypo-enhancing areas can also be seen within the lesions and are attributable to hypovascular collagenous stroma.
The role of PET/CT in the differentiation of benign from malignant SFTs is not well established.
- References
- Badawy, M., Nada, A., Crim, J., Kabeel, K., Layfield, L., Shaaban, A., Elsayes, K. M., & Gaballah, A. H. (2022). Solitary fibrous tumors: Clinical and imaging features from head to toe. European Journal of Radiology, 146, [110053]. https://doi.org/10.1016/j.ejrad.2021.110053
Demicco, E.G., Wagner, M.J., Maki, R.G., Gupta, V., Iofin, I., Lazar, A.J., Wang, W.-L. (2017). Risk assessment in solitary fibrous tumors: Validation and refinement of a risk stratification model Modern Pathology, 30 (10), pp. 1433-1442.
J.H. Choi, J.Y. Ro (2021). The 2020 WHO classification of tumors of soft tissue: selected changes and new entities Adv. Anat. Pathol., 28 (1), pp. 44-58, 10.1097/PAP.0000000000000284
- Keywords
- Solitary fibrous tumor of the pleura,