Pedunculated localized fibrous tumor of the pleura presenting as a moving chest mass.

Abstract: Localized fibrous tumor of the pleura is a rare primary pleural neoplasm. The tumors are usually discovered incidentally on routine chest radiography. A change in the lesion's position with respiration and/or posture of the patient indicates a pedunculated pleural lesion. Computed tomography and magnetic resonance imaging reveal the relation of the lesions to adjacent structures. Magnetic resonance imaging is also useful for the characterization of the lesions on the basis of signal features. These tumors usually consist of mature fibrous tissue.

Key Words: chest radiography, computed tomography, localized fibrous tumor, magnetic resonance imaging, neoplasm, pleura

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Localized fibrous tumor of the pleura is a rare tumor that accounts for less than 5% of all pleural neoplasms. (1) Most of the patients are asymptomatic, and the lesions are discovered incidentally. The tumors can arise anywhere from the pleura and can be attached to the pleura with a peduncle. (1-3) We present a case of a mass localized in the right major fissure, attached to the pleura with a peduncle, which changes in position, depending on the patient's posture.

Case Report

The chest radiograph of a 46-year-old woman taken before cholecystectomy revealed the presence of a right-sided thoracic mass. She had no pulmonary symptoms. Her physical examination and laboratory findings were unremarkable. The only finding was dullness on the right hemithorax.

The lesion, 12 X 10 X 5 cm in size, was seen in the right lower hemithorax and was located anteriorly on the lateral view (Fig. 1, A and B). In the supine position, the mass moved superiorly from the right costophrenic angle (Fig. 2). Computed tomography (CT) scan revealed a well-defined, nonhomogeneous soft tissue density mass within the right major fissure (Fig. 3). Magnetic resonance imaging showed heterogenous signal intensities on both T1- and T2-weighted images. Areas of low and high signal features were seen in both sequences (Fig. 4, A and B).

A presumptive diagnosis of pedunculated benign tumor of the pleura was made. Elective exploratory thoracotomy was performed and revealed a lesion located in the oblique fissure, attached to the middle lobe with a thin fibrous band. On macroscopic examination, the lesion was a hard, capsulated, and lobulated mass, which was 12 X 12 X 5.5 cm in size. Histopathology showed densely packed collagen fiber proliferation in between small, uniform tumor cells with spindle-shaped or round nuclei and narrow cytoplasms. Mitotic activation was very low, and it was found to be 0 to 1. No necrosis was seen. On immunohistochemical examination, strong and diffuse CD34 positivity was found in the cytoplasms of the tumor cells. Also, BCL2 positivity was found in most of the tumor cells. Benign localized fibrous tumor was diagnosed (Fig. 5). The patient remains asymptomatic 1 year after surgery.

Discussion

Localized fibrous tumor of the pleura, also termed fibrous mesothelioma or benign mesothelioma, is a rare primary pleural neoplasm. The pathogenesis is obscure; however, the currently accepted theory is derivation from submesothelial mesenchymal cells with a fibroblastic differentiation. (4) The tumors mostly originate from the visceral pleura (70%) and are often pedunculated, with the stalk containing prominent vessels. Although in the majority of cases the tumors are histologically benign, malignant subtypes are recognized. (4)

Localized fibrous tumor of the pleura most commonly present in middle age, and the lesions are usually incidentally discovered. There is a slightly higher incidence in women, and occurrence is equal in the right and left hemithorax. Signs and symptoms, if any, are usually associated with larger tumors and occur more frequently in malignant subtypes. The most common symptoms are cough, chest pain, and dyspnea. Hypoglycemia and hypertrophic osteoarthropathy have been reported in solitary fibrous tumors of the pleura. (5-8)

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The pathologic features of the tumors depend on the size of the lesion. Small lesions (less than 8 cm) are nodular and embedded within the lung beneath and attached to a smooth pleural surface. Large lesions, as in our case, protrude into the pleural cavity with a vascular pedicle attached to the visceral pleura and are covered by adhesions. Cut sections reveal a firm, glistening, gray or white surface with a whorled pattern. On histologic examination, the lesions consist of spindle-shaped cells separated by collagen. Edema, hemorrhage, and necrosis are present in the large lesions. (2,4,8)

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On chest radiography, the lesions appear as round or oval, often lobulated masses, located at the pleural surface. Pedunculated lesions show positional variation with changes in position and respiration. (5-7) In some cases, the pedicle of the tumor can twist and the tumor detaches itself from the pleura, forming a mobile intrathoracic mass. (9) Fissural lesions can simulate intrapulmonary masses or intrafissural fluid collections. (6)

CT appearance depends on the size of the tumor. (10) Small lesions have a homogenous appearance, but large tumors show heterogenous enhancement containing tubular or round low-density areas associated with myxoid degeneration, necrosis, and hemorrhage. Large lesions may cause compression atelectasis in the adjacent lung. There is rarely chest wall invasion. Calcifications have been reported in less than 5% of cases, mostly in large tumors. (2,3,5)

Conclusion

Magnetic resonance imaging can reveal the morphology of the lesion and the relation of the tumor to adjacent structures. (3,5) It can also be useful for the characterization of the tissues on the basis of signal intensity.

An incidentally discovered tumor of the pleura found in a healthy person usually indicates a benign lesion. Positional changes on chest radiography and significant enhancement of the lesion on CT scan after intravenous contrast administration confirm the diagnosis.

Accepted July 11, 2004.

References

1. Theros EG, Feigin DS. Pleural tumors and pulmonary tumors: differential diagnosis. Semin Roentgenol 1977;12:239-247.

2. Lee KS, Im J, Choe KO, et al. CT findings in benign fibrous mesothelioma of the pleura: pathologic correlation in nine patients. AJR 1992;158:983-986.

3. Ferretti GR, Chiles C, Cox JE, et al. Localized benign fibrous tumours of the pleura: MR appearance. J Comput Assist Tomogr 1997;21:115-120.

4. England DM, Hochholcer L, McCarthy MJ. Localized benign and malignant fibrous tumor of the pleura: a clinicopathologic review of 223 cases. Am J Surg Pathol 1989;13:640-658.

5. Rosado-de-Christenson ML, Abbott GF, McAdams HP, et al. Localized fibrous tumours of the pleura. Radiographics 2003;23:759-783.

6. Karabulut N, Goodman LR. Pedunculated solitary fibrous tumour of the interlobar fissure: a wandering chest mass. AJR 1999;173:476-477.

7. Lewis MI, Horak DA, Yellin A, et al. The case of the moving intrathoracic mass. Chest 1985;6:897-898.

8. Briselli M, Mark EJ, Dickersin R. Solitary fibrous tumours of the pleura. Cancer 1981;47:2678-2689.

9. Mengeot PM, Gailly CH. Spontaneous detachment of benign mesothelioma into the pleural space and removal during pleuroscopy. Eur J Respir Dis 1986;68:141-145.

10. Harris N, Rozenshtein A, Schiff MJ. Benign fibrous mesothelioma of the pleura: MR imaging findings. AJR 1995;165:1143-1144.

RELATED ARTICLE: Key Points

* Lesions that show positional variation with changes in posture and respiration are of pleural origin and are generally pedunculated.

* In a healthy person, an incidentally found pleural mass that changes position is usually benign.

* The relation of the tumor to adjacent structures is evaluated by cross-sectional imaging.

Canan Akman, MD, Serap Cetinkaya, MD, Sila Ulus, MD, Kamil Kaynak, MD, and Buge Oz, MD

From the Medical Faculty, Radiology Department, Thoracic Surgery, and Pathology Department, Istanbul, Turkey.

Reprint requests to Dr. Canan Akman, Istanbul University Cerrahpasa Medical Faculty, Radiology Department, Cerrahpasa, Istanbul, Turkey. E-mail: [e-mail]