Solitary fibrous tumor of the pleura (SFTP) is an uncommon disease, and only about 800 cases have been described in the literature. There are 2 distinct types: the local, benign form, and the more uncommon, highly aggressive diffuse form.1,2 It can appear at any age, although it is more common in patients between 60 and 70 years of age. It begins as an intrathoracic pleomorphic mass, requiring a differential diagnosis considering benign and malignant pleuropulmonary lesions. Histopathological analysis is essential for reaching the right diagnosis.

We report the case of a 55-year-old woman, non-smoker with no significant clinical history, who presented with chest pain after an injury. A chest X-ray was performed, which fortuitously revealed a right pleuropulmonary tumor. The patient had no respiratory symptoms and lung function test results were normal. A computed axial tomography (CAT) of the chest was obtained for further investigation, showing a tumor in the lower third of the right hemithorax, in close proximity to the diaphragm and cardiomediastinal structures (Fig. 1). Fine needle biopsy revealed tissue consistent with spindle cell mesenchymal tumor. In view of these findings, the patient underwent the routine surgical procedure and the tumor was fully resected. Pathological analysis confirmed a solitary fibrous tumor with areas of spindle cells with a high mitotic index, significant pleomorphism and high cellularity (meeting the malignancy criteria of England et al.). Immunohistochemistry was positive for vimentin and CD34.3 Adjuvant treatment was ruled out due to the low chemosensitivity of this tumor strain and the lack of data in this respect. Routine monitoring was performed until 1 year later, when 2 apparently malignant nodular lesions, very close to each other (18mm and 13mm), were seen on a follow-up CAT. These lesions were subsequently resected. Pathological findings confirmed tumor compatible with SFTP metastasis. Six months later, multiple nodules were observed in both lungs on a repeat CAT, and bone involvement was confirmed by scintigraphy. After evaluation by the medical oncology department, c-KIT mutation determination was ordered, in view of reports of long periods of response with imatinib associated with this mutation.4 In the end, however, the tumor was c-KIT negative, so chemotherapy was started. Despite the various treatment lines administered, disease progression was rapid and the patient died shortly after the diagnosis of relapse.

Fig. 1.

Computed axial tomography.

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This case illustrates 2 interesting aspects. Firstly, the appearance of SFTP, an uncommon tumor that presents with generalized symptoms, and must be considered as part of the differential diagnosis of pleural masses. Secondly, the disease appeared to begin as a non-aggressive type, although the histopathological finding suggested it was high risk. It subsequently gradually developed to a highly aggressive form. These findings underline that little is known about this tumor and its natural history, and that treatment options are limited.