Giant Solitary Fibrous Tumor of Pleura in Patient Submitted to Surgical Treatment

Solitary fibrous tumor (SFT) of the pleura is a rare tumor of an unknown cause and corresponds to 5% of all pleural tumors. It is generally asymptomatic and discovered incidentally through imaging exams. The definitive diagnosis is based on histopathological findings and treatment is surgical. This paper describes the case of a previously healthy female patient with a tumor mass at the base of the left lung.


Introduction
Solitary fibrous tumor (SFT) of the pleura is rare and the cause remains unknown 1 . Although more common in the pleurae, SFT can also be found in the pericardium, mediastinum, heart and extra-thoracic locations, such as the thyroid gland, adrenal gland and bladder, which suggests an origin starting from pluripotent cells of the fibrous mesenchyme with myofibroblastic characteristics 2 .
SFT corresponds to 5% of all pleural tumors, affecting approximately 2.8 of every 100,000 individuals 2 . Most cases are diagnosed between the fourth and seventh decade of life and the incidence is similar between men and women 3 . The literature describes approximately 800 cases 4 .
Pleural SFT is generally asymptomatic and discovered incidentally by radiography performed for other reasons 5 . The non-specific clinical manifestations make imaging diagnostic methods and biopsy guided by computed tomography (CT) essential for the diagnosis. Definitive treatment is surgical and relapse can occur 6 . This paper reports the case of a patient with a giant solitary fibrous tumor of the pleura submitted to surgical treatment.   Pulmonary plethysmography revealed a mild reduction in forced vital capacity (73% of predicted), with preserved volume residual and RV/FVC ratio compatible with a mild restrictive disorder.

Case Presentation
Following CT-guided biopsy (Figure 3), the anatomopathological findings revealed a solitary fibrous tumor with dense stromal hyalinization and negative for malignancy. The anatomopathological analysis revealed a pleural solitary fibrous tumor measuring 18.2 x 17.0 x 9.5 cm and weighing 1398 g, with extensive collagenization and areas of necrosis associated to focal points of both old and recent thrombosis in organization, with the surgical margin free of neoplasm ( Figure 4).
Approximately six months after surgery, with the patient asymptomatic, the follow-up chest CT revealed complete preservation of the pulmonary parenchyma and no sign of recurrence ( Figure 5).

Discussion
In the majority of cases, pleural SFT is asymptomatic in the early phase. However, with the growth of the tumor mass, some symptoms may appear, such as cough, chest pain, dyspnea and hemoptysis, with local pain as the most common symptom 7 . In the present case, the patient complained of a mild pain in the left hemithorax.
In cases of tumors with a larger volume, paraneoplastic symptoms may be reported, such as hypertrophic arthropathy, digital clubbing, gynecomastia, galactorrhea and hypoglycemia 8 . None of these symptoms were reported by the patient in the present case.
Benign pleural SFTs have vascularization through a pedicle linked to the pleura and have considerable mobility 9 . In the present case, these characteristics were identified in the intraoperative period.
Despite the contribution of diagnostic imaging methods, such as radiography and CT, to the detection of pleural tumors, the "gold standard" remains biopsy, which was guided by CT in the present case. Despite being an invasive procedure, biopsy is fundamental to the precise diagnosis.
In cases of pleural SFT, definitive treatment is surgical. As there were no adherences or invasion of the tumor into the pulmonary parenchyma, lobectomy was not indicated, and the patient was submitted to left thoracotomy for excision of the tumor mass 8 .

Conclusion
In this report, a patient with a giant solitary fibrous tumor was submitted to surgical treatment, which achieved a satisfactory result with no intraoperative or postoperative complications and with complete preservation of the left lung.