Malignant giant solitary fibrous tumor of the pleura metastatic to the thyroid gland.

Purpose: Solitary fibrous tumor (SFT) of the pleura is a rare mesenchymal neoplasm arising from mesenchymal cells in the areolar tissue subjacent to the mesothelial-lined pleura and accounting for less than 5% of primary pleural tumors. SFTs are generally benign and asymptomatic, with 10-year survival rates of up to 98%. Unfortunately, approximately 10% have malignant potential, leading to local recurrence after radical surgery and/or metastatic spread. Of note, giant pleural SFT, which consists of a tumor occupying at least 40% of the affected hemithorax, is even less common with only anecdotal cases reported in the medical literature.

Methods: We describe a unique case of giant SFT of the pleura that metastasized to the thyroid gland 1 year after complete resection, focusing on its clinical and pathological features of presentation.

Results: En bloc resection remains the mainstay of therapy with curative intent. Patients with large tumors may undergo preoperative angiography with percutaneous embolization of the tumor, which allows to reduce perioperative bleeding. In case of local recurrence, surgery still remains the best treatment option. However, surgery can also be considered in patients with isolated metastatic spread.

Conclusions: Every suspected and proven SFT of the pleura should undergo surgical resection, as clinical and radiological criteria cannot accurately distinguish benign from malignant forms. Moreover, the peculiar histological features of SFT should not be neglected when planning clinicoradiological follow-up. Additionally, suspicious clinical findings during follow-up should always be thoroughly investigated in order to exclude or confirm the diagnosis of recurrent disease.