Pleural Fibromas: A Clinical Review and Report of Six Patients. R. W. Bunton, M.B., Ch.B., and J. Borrie, Ch.M., F.R.C.S., F.R.A.C.S.

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1 Pleural Fibromas: A Clinical Review and Report of Six Patients R. W. Bunton, M.B., Ch.B., and J. Borrie, Ch.M., F.R.C.S., F.R.A.C.S. ABSTRACT Localized pleural fibromas are a definite clinical entity. Their origin is much debated. Though most arise from the mesothelial cell, occasionally some arise from the pleural fibroblast. The former retain the potential to become malignant. Distinguishing between the two origins can aid prognosis after treatment. The characteristic cell is a spindle-shaped fibroblast. Slits or clefts lined by flattened cells are often present in the tumor. Clinically, pleural fibromas are usually asymptomatic, space-occupying lesions. Chest symptoms are nonspecific. Extrathoracic symptoms, especially arthritis, are not uncommon and occur only in the benign variety. Excision is the treatment of choice, but long-term follow-up is essential, for recurrence is not unknown and is often heralded by the return of arthritic symptoms. Recurrences may be benign or malignant, the latter having a poor prognosis, with most patients dying within 2 years. Experience with benign pleural fibromas seen in 6 patients over a 25- year period is presented. In general, it is now accepted that primary pleural tumors do exist. In 1931, Klemperer and Rabin [13 classified them as localized or diffuse, according to morphological features. The localized form has many names, the most common being pleural fibroma. Its exact cellular origin is still debated; its clinical course is variable. This paper concerns the localized forms, and discusses the cases of 6 patients in relation to published reports. Localized lung cancer was the chief differential diagnosis in all patients. From the Thoracic Surgical Unit, Dunedin Hospital, and the Department of Surgery, University of Otago Medical School, Dunedin, New Zealand. Accepted for publication Oct 13, Address reprint requests to Dr. Bunton, Department of Surgery, University of Otago Medical School, P.O. Box 913, Dunedin, New Zealand. Case Reports Patient 1 A 60-year-old asymptomatic, nonsmoking man had a routine examination. A roentgenogram of the chest showed a mass in the left upper thorax anteriorly. Results of physical examination, bronchoscopy, sputum cytology, and a liver scan were normal. At thoracotomy, a mass arising from the parietal pleura was dissected out in the extrapleural plane (Fig 1). The lesion measured 3.5 cm in greatest diameter. Histological examination revealed a densely collagenous tumor of variable cellularity and composed mainly of spindle-shaped cells arranged in bundles. The tumor had clefts lined by flattened and cuboidal cells. No evidence of malignancy was found. Follow-up at 1 year showed no recurrence. Patient 2 A 63-year-old asymptomatic woman underwent a routine examination. A chest roentgenogram showed a coin lesion in the apical segment of the right lower lobe. She had smoked twentyfive cigarettes a day for 1.5 years. Results of physical examination, bronchoscopy, sputum cytology, and Ziehl-Neelsen staining were negative. Thoracotomy revealed a pedunculated tumor arising from the visceral pleura of the apical segment of the right lower lobe (Fig 2). A wedge resection was done. Histologically, the lesion was a densely collagenous tumor consisting of regular-shaped spindle cells. Distorted air spaces lined by cuboidal epithelial cells enclosed within the fibrous tissue were seen at the junction of the tumor with lung parenchyma. There was no evidence of malignancy, and 6-year follow-up revealed no recurrence. Patient 3 A SO-year-old man was seen after a year of increasing productive cough and six months of by The Society of Thoracic Surgeons

2 610 The Annals of Thoracic Surgery Vol 33 No 6 June 1982 tumor to be densely collagenous with a few fibroblasts and with cystic spaces lined by endothelial-like cells. There was no sign of malignancy, and 21-year follow-up revealed no recurrence. Fig 1. (Patient 1). Operative photograph showing the lesion arising from the parietal pleura. Fig 2. (Patient 2). Operative photograph showing the tumor arising from the visceral pleura of the apical segment of the right lower lobe. dull chest pain on the left sternal border. He had finger clubbing, and a chest roentgenogram showed an opacity anteriorly in the left lung. The Mantoux and Casoni tests gave negative results. At thoracotomy, a pedunculated tumor arising from the lingula was removed by wedge resection. Histological examination showed the Patient 4 A 52-year-old asymptomatic man, who had smoked twenty cigarettes a day for the past 12 years, was admitted after routine chest roentgenograms showed a rounded lesion anteriorly in the left hemithorax. Physical examination was normal. Thoracotomy revealed a pedunculated tumor arising from the parietal pleura at the front of the second rib. The tumor and adjacent ribs were excised. Histological evaluation revealed a densely collagenous tumor containing spindle-shaped cells, without malignancy. Follow-up of 4 years showed no recurrence. Patient 5 A 60-year-old man with chronic bronchitis, who smoked 60 gm of tobacco a week, was seen with a 2-year history of increasing shortness of breath, nocturnal wheeze, and a left-sided subscapular pain, which was nonpleuritic and nonradiating. For 5 years he had been exposed to asbestos. Physical examination suggested chronic airway obstruction. A chest roentgenogram revealed a left-sided pleural opacity and an irregular left hemidiaphragm. A preoperative diagnosis of malignant mesothelioma was made. At thoracotomy, the roentgenographic abnormalities were found to be caused by extensive pleural plaques, confirmed by frozensection biopsy and histological study with paraffin block. A small nodule, not seen in the chest roentgenogram and palpated in the left lower lobe as a firm, mobile tumor 3 mm in diameter, was removed. Histological study confirmed dense, fibrous tissue divided into nodules by clefts lined with flattened cells; there was no evidence of malignancy. Threeyear follow-up has not shown recurrence. Patient 6 A 60-year-old man had undergone a left eighth intercostal transthoracic hiatal herniorrhaphy when he was 57 years old. A routine chest

3 611 Bunton and Borrie: Pleural Fibromas roentgenogram made 3 years later showed a tumor in the anterior aspect of the left chest wall in the region of the fourth and fifth ribs. At thoracotomy, a sessile tumor, found growing from the parietal pleura, was removed en bloc with subjacent portions of the fourth and fifth ribs. The chest wall defect was repaired with tantalum mesh. Histologically, the lesion was a cellular, collagenous tumor covered on its external aspect by flattened cuboidal cells continuous with the pleura. There was no rib or muscle involvement, and no evidence of malignancy. Nine-year follow-up showed no recurrence. Comment In 1931 Klemperer and Rabin [l] were among the first to try to bring order to the confused writings on pleural tumors. They classified them as localized or diffuse and stated that while the diffuse type arose from the pleural surface-lining cells, the localized form arose deep to this layer. They did not clarify whether this meant pleural connective tissue or extrapleural connective tissue. Friedman [2] and Clagett and co-workers [3] attributed the origin to the subserous connective tissue. Edwards [41 and Friedman [2] noted that tumors arising in extrapleural connective tissue sometimes had been described as pleural in origin-erroneously. Metastatic disease, endotheliomas arising from vessels, and pulmonary epithelial tissue remnants could also be the source [5]. Brown and Johnson [6] postulated that pleural tumors arose from proliferation of mesothelial or connective tissue cells in postpneumonic effusions high in protein and low in polymorphonuclear leukocytes. The second patient in the report [7] of Shabanah and Sayegh [71 experienced blunt chest trauma 5 years before the tumor was found during routine examination. Our Patient 6 had a left thoracotomy 3 years before a pleural tumor was discovered on a biannual chest roentgenogram. Whether there is a true trauma-link is difficult to prove. Maximow [8] and Sano and associates [9] demonstrated with tissue culture experiments that mesothelial cells can become epithelial or fibrous tissue. They also showed microscopically the transition between the epithelial and fibrous stromal cells. Godwin [lo] postulated that mesothelial cells could produce both the localized and diffuse forms of pleural tumors. Although Shabanah and Sayegh [7] stated that all solitary fibrous pleural tumors arose from the surface mesothelium, no mesothelial cells can be demonstrated in some tumors [ll, 121, and the subpleural fibroblast is thought to be a rare progenitor of these tumors. Bracco [13] thought it impossible to distinguish two types of pleural fibroma-one arising from mesothelium and the other from pleural connective tissue. He [13] and Klima and Gyorkey [14] maintained that tumors arising from the mesothelium retain the potential to become malignant, while those arising from connective tissue tend to remain benign. Electron microscopy can distinguish between the two and thus is important in assessing prognosis. Pleural fibromas can occur at any age, most commonly in the fifth decade, with equal frequency in either pleural cavity. They vary greatly in size. While the fibroma in Patient 5 in our Dunedin series was only 3 mm in diameter, Clagett and Hausmann [15] removed one measuring 36 X 22 X 11 cm. These tumors arise more commonly from the visceral pleura and in 50% of patients are pedunculated. In the review by Okike and colleagues [16] of the Mayo Clinic series, no malignant tumor was pedunculated. Most have a lobulated surface, are pale to tan in color, and are usually encapsulated [3, 16, 171. Histologically, pleural fibromas are fibrous with varying degrees of cellularity. The tumors described by Klemperer and Rabin [l] as giant sarcomas of visceral pleura were undoubtedly cellular fibromas [17]. Rarely, they may be totally cellular 1. Stout and Murray [5] and Sano and associates [9] claimed that fibromas never have epithelial elements, but this is not so. The typical cells are spindle-shaped fibroblasts. Slits or clefts lined by flattened, cuboidal, or epithelial-like cells are often present, as in our Patients 1, 2, 3, and 5, and are not a feature of ordinary connective tissue fibromas [3, 191. Luse and Spjut [20] found that the cells in their patient were mesothelial, while Wang [ll] found them to be endothelial cells lining capillaries. Trapping of pulmonary epithelium within rapidly growing fibrous tumors is also

4 612 The Annals of Thoracic Surgery Val 33 No 6 June 1982 possible [ll], as seen in our Patient 3. They may also represent cuboidal metaplasia of pulmonary epithelium following stromal fibrosis. When present, the slit-like spaces possibly indicate a mesothebal origin [12]. The tumors are often discovered on chance roentgenograms of the chest, as in Patients 1,2, 4, and 6. Symptoms, when present, may be cough, chest pain, and shortness of breath. Clagett and colleagues [3] found 60% of their patients had joint symptoms and 11 of 24 had clubbing. Chills and fever were found in 7 of 24. PriceThomas and Drew [21l, describing 6 patients with visceral pleural fibromas, found 4 with symptoms of rheumatism, and 3 with joint pain, swelling, and tenderness. Okike and associates [16] also found significant extrathoracic symptoms in their series, 17% of patients having fever and 19% with joint symptoms and clubbing. These extrathoracic symptoms were present oniy in patients with benign tumors, especially if the tumor was large. The easing of joint symptoms following tumor resection is well documented [3,16, 211. Relapse of arthritic symptoms following excision may indicate recurrence of tumor [16, 211. Clagett and coworkers 131 suggested such symptoms may be due to the production of hyaluronidase from the glandular-like spaces, but presented no supporting evidence. In our series, only Patient 3 had finger clubbing. None had rheumatism as a primary complaint. With no clinical, radiological, or biochemical tests to aid diagnosis, and unless otherwise contraindicated, thoracotomy with excision is the treatment of choice. Unless it is removed, an isolated lung cancer cannot be excluded. Surgical removal is usually curative, but fibromas can and do recur. Klemperer and Rabin El], who reported the case of a patient with a malignant recurrence 4 years after removal of a tumor, wondered whether the previous operation had indeed altered the natural history of the tumor. Clagett and co-workers [3] reported four fatal recurrences. The histology of these tumors was no different from the original tumors. Kerr and Noh1 [22], describing fatal recurrences with sarcomatous changes, emphasized that clinical and pathological progression toward malignancy occurs with repeated recurrences. However, the end is unpredictable. Utley and associates [23] described recurrences that were still "benign on histological criteria" 5 to 6 years postoperatively. Three years after a second operation, their Patient 2 again had a "benign'' recurrence, which was removed at a third operation. At the time the paper was written, all their patients were alive. Scattini and Orsi [24], on the other hand, reported spontaneous regression of pleural fibromas. Okike and co-workers El61 found that on histological criteria, 8 of the 60 patients in their study had malignant localized pleural fibromas. Of the 7 who survived excision, 6 died within 2 years. The survival curve for the 52 patients with benign fibromas surgically removed was the same as that for the general population. Two of these tumors recurred; one was benign and one was malignant, but still localized. The patient with a benign recurrence noted a return of arthritic symptoms, which had been "cured" by the earlier operation. In our series, there were no recurrences. Regarding the origin of recurrences after resection, Bracco [13] and Klima and Gyorkey [14] suggested that those arising from the submesothelial connective tissue tend to remain benign, while those arising from the mesothelium retain the potential for malignant transformation. This distinction can be important when predicting the prognosis for individual patients after operation, and electron microscopy is necessary to distinguish between the two cellular types. Routine follow-up with regular chest roentgenograms is clearly essential. References 1. Klemperer P, Rabin CB: Primary neoplasms of the pleura. Arch Pathol 11: , Friedman LL: Tumors of the pleura. Dis Chest 17: , Clagett OT, McDonald JR, Schmidt HW: Localised fibrous mesothelioma of the pleura. J Thorac Surg 24: , Edwards AT: The surgical treatment of intrathoracic new growths. Br Med J , 1932

5 613 Bunton and Borrie: Pleural Fibromas 5. Stout AP, Murray MR: Localised pleural mesothelioma. Arch Pathol 34: , Brown WJ, Johnson LC: Postinflammatory tumors of the pleura. Milit Surg 109: , Shabanah FH, Sayegh SF: Solitary (localised) pleural mesothelioma. Chest 60: , Maximow A: Arch Exp Zellforsch 41:1927. Quoted in Stout and Murray [51 9. Sano ME, Weiss E, Gault ES: Pleural mesothelioma. J Thorac Surg 19: , Godwin MC: Diffuse mesotheliomas. Cancer 10: , Wang Nai San: Electron microscopy in the diagnosis of pleural mesotheliomas. Cancer 31: , Hernandez FJ, Fernandez BB: Localised fibrous tumors of pleura: a light and electron microscopy study. Cancer 34: , Bracco AN: Mesoteliomas malignos de la pleura. Rev Asoc Medica Argent 78:74, Quoted in Scattini and Orsi [14] 14. Klima M, Gyorkey F: Benign pleural lesions and malignant mesothelioma. Virchows Arch [Pathol Anat] 376: , Clagett OT, Hausmann PF: Huge intrathoracic fibroma: report of a case. J Thorac Surg 13:6-15, Okike N, Bernatz PE, Woolner LB: Localised mesothelioma of the pleura. J Thorac Cardiovasc Surg 75: , Madani MA, Schwartz HF, Gershon NR: Fibroma of pleura: a case report. Can J Surg 16: , Yesner R, Hurwitz A: Localised pleural mesothelioma of epithelial type. J Thorac Surg 26: , Sabiston DC, Spencer FC: Gibbon s Surgery of the Chest. Third edition. Philadelphia, Saunders, 1976, pp Luse SA, Spjut HJ: An electron microscopic study of a solitary pleural mesothelioma. Cancer 17: , Price-Thomas C, Drew CE: Fibroma of the visceral pleura. Thorax 8: , Kerr WF, Noh1 HC: Recurrence of benign intrathoracic fibromas. Thorax 16: , Utley JR, Parker JC, Hahn RS et al: Recurrent benign fibrous mesothelioma of the pleura. J Thorac Cardiovasc Surg 65: , Scattini CM, Orsi A: Multiple bilateral fibromas of the pleura. Thorax 28: , 1973