Clinical History
Patient referred to our Hospital for staging melanoma in April 2007. He was non-smoker, asymptomatic and in good general condition. Physical examination and laboratory blood tests were within the normal limits. CT examination of the chest, abdomen, pelvis and head was performed.
Imaging Findings
Chest CT scans (axial images and multiplanar reconstructions) (Figures 1-5) at lung window setting demonstrates in the left hemithorax a well-marginated ovoid mass attached to the fissural pleura with a small pedicle. The mass predominantly forms obtuse angles with the fissure. CT scans at mediastinal window setting, assessed before and after contrast medium injection, show a solid mass with a considerable enhancement (50 HU) (Figures 2 and 3). No hilar and mediastinal lymph nodes are detected. No abnormalities in the brain, abdomen and pelvis were found.
The retrospective evaluation of chest radiographs obtained 11 years before (1996) showed a small ovoid well-defined opacity along the course of the left fissure (Figure 6).
The mass was surgically resected.
Discussion
Solitary Fibrous Tumors of the pleura (SFTP) are rare primary mesenchymal neoplasms that can arise anywhere along the pleura and can even be seen along the pulmonary fissures (4%). The tumor is often attached by a pedicle to the pleura.
SFTP represent about 17% of all benign intrathoracic tumors. It can grow slowly and potentially become big masses with a malignant behaviour and metastases. The ratio between benign and malignant forms is 7:1. Histochemistry is necessary for differentiation between benign or malignant lesions.
SFTP is asymptomatic in over 50% of cases and mostly found incidentally. Symptoms (chest pain, dyspnea, cough) tend to be more common in larger lesions. The prognosis is generally favourable and the therapy is surgery, being the complete surgical excision the best prognostic factor. Recurrence has been reported in up to 16% of the non-peduncolated cases.
Chest radiography usually shows a well-defined, homogeneous and rounded mass. While small tumors which arise from the parietal pleural classically form obtuse angles with the chest wall, large or peduncolated lesions form acute angles and may be confused with intrapulmonary masses. Computed tomography (CT) usually demonstrates a well-delineated, homogeneous, and occasionally lobulated solid mass in contact with the pleural surface. On contrast-enhanced CT scans the lesion enhances more than the soft tissue does, because of its rich vascularisation. Tumor arising in an interlobar fissure may be more difficult to differentiate from an intraparenchymal mass, because the lesion appears to be surrounded by lung parenchyma. Evaluation of morphology, margins and angles of the mass with respect to the fissure as well as the identification of a pedicle which connects the lesion to the fissural pleura may help in differential diagnosis and in treatment planning. Thin-section CT scans with multiplanar reformations better depict the relationship of the mass to the pleura. MR imaging can better demonstrate the fibrous character of the lesion.
Other possible differential diagnoses include intrafissural effusion, that demonstrates fluid attenuation and does not show enhancement after contrast medium injection; malignant pleural mesothelioma that nearly always shows nodular focal or diffuse circumferential thickening of the pleura that encases the hemithorax; pleural metastasis that are more commonly multiple lesions and may show heterogeneous density, calcification and sometimes irregular margins. Pleural effusion is very common in pleural metastases and mesothelioma.
In our case the diagnosis was suspected on the basis of the decribed CT appearances which allowed the identification of a pedicle that connected the mass to the left fissure. Moreover, the lesion was present years before on chest X-rays and showed a low growth over the time, indicative of a benign lesion. At surgery the mass was attached to the fissural visceral pleura with a vascular pedicle and the definite diagnosis was confirmed at specimen and immunohistochemical analysis (figures 7 and 8).
Differential Diagnosis List
Solitary Fibrous Tumor of the left fissural pleura
Localized Malignant Pleural Mesothelioma
Fibrous Tumor of the pleura
Pleural metastasis
Intrafissural pleural effusion
Intraparenchymal pulmonary mass
Final Diagnosis
Solitary Fibrous Tumor of the left fissural pleura
