Ann Thorac Surg 2008;86:1360-1362. doi:10.1016/j.athoracsur.2008.04.014
© 2008 The Society of Thoracic Surgeons
Case Reports
Intrapulmonary Localized Fibrous Tumor of the Lung: A Very Unusual Presentation
Hiroyuki Sakurai, MDa,*,
Wakae Tanaka, MDa,
Masahiro Kaji, MDa,
Kazuto Yamazaki, MDb,
Keiichi Suemasu, MDa
a Department of Thoracic Surgery, Saiseikai Central Hospital, Tokyo, Japan
b Department of Pathology, Saiseikai Central Hospital, Tokyo, Japan
Accepted for publication April 4, 2008.
* Address correspondence to Dr Sakurai, Department of Thoracic Surgery, Saiseikai Central Hospital, 1-4-17, Mita, Minato-ku, Tokyo, 108-0073, Japan (Email: sakuraihm{at}ybb.ne.jp).
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Abstract
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Most localized fibrous tumors arise from the visceral pleura on a stalk and project into the pleural cavity in a pedunculated manner. The origin of the tumors is now believed not to be mesothelial but rather submesothelial, based on studies using conventional histology, immunohistochemistry, and ultrastructural analysis. While inward tumor growth into the lung parenchyma with attachment to the pleura is uncommon, the tumor with an entirely pulmonary location is extremely rare. We present here a rare case of entirely intrapulmonary localized fibrous tumor (ie, localized fibrous tumor of the lung), and we review the pertinent literature.
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Introduction
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Localized fibrous tumors are neoplasms that usually arise from the pleura, especially visceral pleura [1–3]. In regard to localized fibrous tumors arising from the pleura, the clinicopathologic features have been discussed elsewhere [1–3]. Most of these tumors project into the pleural cavity in a pedunculated manner from the visceral pleura, and their histologically benign features and growth on a pedicle are known to indicate a favorable clinical course [2]. While inward tumor growth into the lung parenchyma from the visceral pleura is infrequent [3], thoroughly intrapulmonary localized fibrous tumors without histologic attachment to the visceral pleura have been described only rarely [4, 5]. Little is known about the clinical behaviors and histologic features of intrapulmonary localized fibrous tumors due to this dearth of material.
We report here a rare case of intrapulmonary localized fibrous tumor that showed an entirely intraparenchymal lesion of the lung, and we review the relevant literature.
A 45-year-old man presented with an abnormal shadow on a routine chest roentgenogram in August 2006. His family and past history were unremarkable. He had never smoked. A chest roentgenogram showed a 2-cm, well-circumscribed, nodular shadow close to the left hilum of the lung. A chest computed tomography (CT) revealed a nodular lesion partially adjacent to the visceral pleura in the superior segment of the left lower lobe of the lung (Fig 1). The lesion showed enhancement after the intravenous administration of contrast material on CT. There was neither mediastinohilar lymphadenopathy nor pleural effusion. The physical findings were all within normal limits. No abnormalities were found in blood tests. Positron emission tomography using 18-F-fluorodeoxyglucose (FDG) showed negative FDG uptake in the lesion. Four months later, the nodular lesion showed a slight increase in size on CT. Thus, due to a diagnostic confirmation of a pulmonary nodule, surgery was performed in the left lung, and the lesion was removed by a wedge resection of the lower lobe through thoracotomy in December 2006. Pathologically, intraoperative frozen sections of the lesion showed benign spindle cell proliferation. The postoperative course was uneventful.
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Fig 1. Chest computed tomographic scan on the lung window shows a well-circumscribed nodular lesion (arrow) in the left lower lobe of the lung.
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In the resected specimen, the tumor had its greatest dimension of 2.2 cm and was elastic and firm, and the cut surface of the tumor showed a well-circumscribed and whitish nodule covered by smooth visceral pleura. Pathologically, the tumor showed a "patternless pattern" proliferation of spindle cells, with regions of hypercellularity admixed with hypocellular regions, accompanied by a collagenous stroma. The tumor was separated from the visceral pleura (Fig 2). The tumor had no evidence of increased mitotic activity, significant atypia, or necrosis. At the periphery of the lesion, compressed lung tissue was seen. Immunohistochemically, tumor cells were positive for vimentin, CD34, and bcl-2. They were negative for cytokeratin, desmins, alfa-smooth muscle actin, and S-100 protein. In addition, a focus of entrapped bronchiolar epithelium, which was demonstrated based on positivity for thyroid transcription factor-1, was seen within the tumor (Fig 3). The firm diagnosis was intrapulmonary benign localized fibrous tumor. The patient is well with no evidence of recurrence 14 months after the operation.
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Fig 2. Photomicrograph shows a tumor close to, but not directly abutting, the visceral pleura. (Hematoxylin & eosin, x50 original magnification.)
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Fig 3. Photomicrograph shows a proliferation of spindle cells in a haphazard arrangement and a focus of entrapped bronchiolar epithelium within the tumor. (Hematoxylin & eosin, x100 original magnification.)
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Comment
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Currently, localized fibrous tumors are widely recognized as submesothelial in origin based on immunohistochemical and ultrastructural findings [2, 3]. These tumors most often involve the pleura, especially the visceral pleura. They are commonly attached to the pleura by a pedicle. The tumors are common during the fifth and sixth decades with no sex predominance [3]. The cause of the tumor remains is unexplained. No association with exposure to asbestos has been documented [3]. Histologically, the tumors are composed of spindle cells with dense bundle collagen, and the spindle tumor cells are arranged in a so-called "patternless pattern" that is characterized by a haphazard distribution of spindle cells and collagen fiber [2, 3]. They are classified as benign or malignant, based on histologic findings (eg, pleomorphism, mitotic activity, invasive growth, or presence of necrosis) [1, 2], although pathologic criteria may slightly differ between observers. Because they lack distinctive histologic features, immunohistochemical examination is very important for their diagnosis. Immunohistochemically, the tumors have been shown to lack expression of cytoplasmic keratin and to express vimentin, a marker of mesenchymal cells [1–5]. In addition, their positive expression of CD34, a transmembrane cell-surface glycoprotein, has recently been shown by several studies, and it is useful for excluding similar spindle-cell neoplasms in differential diagnosis [1, 6].
Most localized fibrous tumors of the pleura are exophytic pedunculated masses that extend from the visceral pleura into the thoracic cavity, and inward growth into the lung parenchyma is rare. When tumors grow into the peripheral lung parenchyma, the term "inverted" has been used to describe such pleural-derived tumors [3]. In the present case, the tumor did not show histologic continuity with the visceral pleura, although it was likely to be macroscopically adjacent to the visceral pleura. In addition, alveolar pneumocytes and small bronchioles that retained their histologically benign appearances were entrapped within fibrous cells of the tumor. Consequently, we considered this tumor to have arisen from the parenchyma of the lung. In fact, early reports of "fibro-adenoma" of the lung may represent this spindle-cell tumor with entrapped alveolar epithelium [7]. As emphasized by Yousem and Flynn [4], these findings could suggest that this localized fibrous tumor arose not from the pleura, but rather from the lung parenchyma itself. Two main hypotheses for their entirely parenchymal location have been proposed [4, 5]. First, the subpleural mesenchyma is in direct continuity with the connective tissue of the interlobular septa, and intrapulmonary fibromas may arise from the septal mesenchyma or invagination of the visceral pleura. Second, these tumors may originate from facultative fibroblastic elements, which can be seen in the submesothelial area of normal pulmonary parenchyma. It has been reported that these elements have ultrastructural and immunohistochemical features similar to those of subpleural connective tissue elements [8]. The present case may reflect the latter hypothesis due to entrapped small bronchioles within the tumor. With such a parenchymal location of the lung, the tumor should not be pathologically mistaken for carcinosarcoma or adenocarcinoma with a metaplastic spindle cell component.
There were 11 previously reported cases of intrapulmonary localized fibrous tumor found in the English literature. Including the present case, they consisted of 8 men and 4 women, ranging in age from 20 to 82 years (mean, 59 years old). The initial symptoms were seen in 3 patients, with cough in 1 patient, arthralgia in another, and chest pain in the other. The tumors ranged in size from 1.0 to 15.0 cm, with a mean of 5.0 cm. The tumors could be located in every lobe of the lung. Histologically, all of the tumors showed benign features. All of the patients, except 1, were treated by complete surgical resection (ie, a wedge resection to a lobectomy of the lung). The exception, reported by Baliga and colleagues in 2007 [9], was treated by radiofrequency ablation because the patient refused surgical treatment, but cardiac shock occurred during the procedure and the patient died. The other patients for whom information could be obtained showed no recurrence after surgery.
Although the prognosis of benign localized fibrous tumors of the pleura is generally good; recurrence has occasionally been reported. de Perrot and colleagues [2] reported significant differences in recurrence and survival according to gross morphologic and pathologic findings. The highest risk of recurrence (ie, a recurrence rate of 63%) was seen in tumors of pathologically malignant and morphologically sessile types, whereas the lowest risk of recurrence (ie, a recurrence rate of less than 2%) was seen in tumors of pathologically benign and morphologically pedunculated types. Morphologically, sessile type is more likely to recur than pedunculated type. To date there has been no report concerning postsurgical recurrence in published intrapulmonary localized fibrous tumors, inclusive of the present case; although the follow-up period after surgery was short in most of the previously reported cases (ie, 3 months to 13 years, with a median of 1 year). The entirely intrapulmonary location of the tumor itself might not necessarily be related to a poor prognosis.
In conclusion, localized fibrous tumor arising from the parenchyma of the lung is extremely rare. The parenchymal occurrence is suggested by the histologic findings of the lack of direct continuity between the tumor and the visceral pleura, and the presence of entrapped alveolar epithelium within the spindle cell proliferation of the tumor. Complete surgical resection has both diagnostic and therapeutic value. However, due to the rarity of intrapulmonary localized fibrous tumors of the lung, a larger number of long-term follow-up cases will be needed to clarify their clinicopathologic behaviors.
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References
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- de Perrot M, Fischer S, Brundler MA, Sekine Y, Keshavjee S. Solitary fibrous tumors of the pleura Ann Thorac Surg 2002;74:285-293.[Abstract/Free Full Text]
- Shields TW, Yeldandi AV. Localized fibrous tumors of the pleuraIn: Shields TW, Locicero III J, Ponn RB, Rusch VW, editors. General thoracic surgery. 6th ed.. Philadelphia, PA: Lippincott Williams and Wilkins; 2005. pp. 889-900.
- Yousem SA, Flynn SD. Intrapulmonary localized fibrous tumor. Intraparenchymal so-called localized fibrous mesothelioma. Am J Clin Pathol 1988;89:365-369.[Medline]
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- Baliga M, Flowers R, Heard K, Siddiqi A, Akhtar I. Solitary fibrous tumor of the lung: a case report with a study of the aspiration biopsy, histopathology, immunohistochemistry, and autopsy findings Diagn Cytopathol 2007;35:239-244.[Medline]
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Abstract
Introduction
