| Abstract|| |
A solitary fibrous tumor of the pleura (SFTP) is an uncommon tumor, in contrast to a relatively common mesothelioma in pleura. Its average size varies from 6 to 8 cm. We report herein a case of a giant SFTP in a 53-year-old man who presented with cough since five years along with chest pain on the left side and progressive dyspnea since two months. Radiological findings revealed a large pleural mass measuring 25 cm in its largest dimension, filling the pleural cavity with effusion. Biopsy showed a spindle cell tumor with areas of dense sclerosis. Subsequent excision unraveled a large multinodular, grey-white tumor, histologically, composed of spindle cells in a 'patternless' arrangement in dense collagenous stroma with areas of hyalinization. Focal areas showed hypercellularity with atypia and mitoses, but less than 4/10 High-Power Field, unassociated with necrosis. On immunohistochemistry, tumor cells showed diffuse positivity with vimentin, CD34 and BCL2 along with cytoplasmic positivity for MIC2 (CD99), whereas cytokeratin, EMA, calretinin and HBME-1 were negative. Diagnosis of an SFTP was substantiated over a close differential of a desmoplastic mesothelioma. In view of atypical features, a close follow-up of the case was recommended.
Keywords: Lung, pleura, solitary fibrous tumor
|How to cite this article:|
Mune S, Rekhi B, More N, Jambhekar NA. A giant solitary fibrous tumor of the pleura: Diagnostic implications in an unusual case with literature review. Indian J Pathol Microbiol 2010;53:544-7
|How to cite this URL:|
Mune S, Rekhi B, More N, Jambhekar NA. A giant solitary fibrous tumor of the pleura: Diagnostic implications in an unusual case with literature review. Indian J Pathol Microbiol [serial online] 2010 [cited 2021 Aug 1];53:544-7. Available from: https://www.ijpmonline.org/text.asp?2010/53/3/544/68289
| Introduction|| |
A solitary fibrous tumor of the pleura (SFTP) is a rare, pleural-based mesenchymal neoplasm that arises from the submesothelial, mesenchymal layer.  Its incidence is approximately 2.8 cases out of 100 000 registered hospitalized patients. It occurs in all age groups with a peak incidence in the fourth and sixth decade of life. ,
Although the majority of these neoplasms are benign, about 10-20% of these cases are malignant.  Average tumor (T) size of a SFTP is 6-8 cm.  Surgical excision forms mainstay of treatment.  Herein, we report a case of a giant SFTP occurring in a 53-year-old male, with its diagnostic implications and role of immunohistochemistry in sorting out its diagnosis from a close histological differential of a spindle cell desmoplastic mesothelioma.
| Case Report|| |
A 53-year-old gentleman presented with left sided chest pain, associated with cough and weight loss of five years duration. The symptoms were progressive with increase in chest pain since two months, along with shortness of breath and alteration in voice. There was no history of hemoptysis, although he had undertaken antitubercular treatment (ATT).
On clinical examination, his general condition was good. There was no clubbing or lymphadenopathy. His hemoglobin was low i.e. 9 gm/dl (normal range 13-17 g/dl), RBC count was low i.e. 3.45 ΄ 10 12 (normal range 4.5-5.5 ΄ 10 12 ) and WBC count was high i.e. 12.9 ΄ 10 9 (normal range 4.0-10.0 ΄ 10 9 ).
Biochemical investigations included high serum alkaline phosphatase i.e. 131 U/L (normal range 30-120 U/L), normal fasting blood glucose level and carcinoembryonic antigen level as 2.86 ng/ml (0.3-2.7 ng/ml).
Sputum examination revealed the growth of group 'A' b-hemolytic streptococci that was sensitive to gentamicin, ofloxacin and ciprofloxacin.
After the exploratory thoracotomy, patient was well, discharged and was recommended follow-up.
Chest X-ray revealed a mass in the left hemithorax with right-sided mediastinal shift.
Ultrasonography revealed left pleural effusion with a mass replacing lung parenchyma.
Computed tomographic (CT) scan of the thorax revealed a large soft tissue mass in the left pleural cavity with compression of the adjacent lung parenchyma [Figure 1].
|Figure 1: Computed tomography (CT) scan solitary fi brous tumor of pleura (SFTP). A large homogenous soft tissue mass (T) in the left hemithorax with compression of the adjacent lung parenchyma|
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99M-TC-MAA lung perfusion scan showed a reduced perfusion in lower two-thirds of the left lung.
Echocardiogram and color Doppler were suggestive of heart being pushed towards the right side due to a mass in the left hemithorax. Left ventricular ejection fraction was 60%.
Gross and Microscopic Findings
An earlier CT-guided biopsy of the mass was diagnosed with differentials of the inflammatory myofibroblastic tumor and fibromatosis. Subsequently, an exploratory thoracotomy unraveled a sessile, well-circumscribed mass, arising from the pleura and measuring 25 ΄ 19 ΄ 10.5 cm in fresh state. The pleura was seen forming reflection over the tumor, resulting in the tumor pseudocapsule. External surface of the tumor was glistening and bosselated. The cut surface was grey-white, firm, multinodular with a whorled appearance and few microcysts. Adjacent lung parenchyma was compressed [Figure 2].
|Figure 2: Macroscopic fi ndings of a SFTP (fi xed specimen). A slice of tumor mass measuring 18 cm in length. Cut surface of a portion of the tumor showing grey white, multi nodular appearance. Central|
liquefacti on not seen A portion of the attached compressed lung tissue with its pleura blending to form the tumor pseudocapsule (arrow)
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Histological examination of multiple sections revealed a tumor composed of predominantly oval to spindle cells amidst abundant dense collagenous stroma. Focal areas showed storiform pattern with alternately hyper- and hypocellular areas and 'slit-like' vasculature. Areas of dense hyalinization were noted. No coagulative tumor necrosis was identified. Cells were relatively bland with focal areas of mild-to-moderate nuclear pleomorphism. Mitotic figures were noted, but were less than 4/10 HPF, with absence of atypical forms. Differential diagnoses were a SFTP and a desmoplastic mesothelioma. Immunohistochemistry (IHC) revealed a diffuse positivity for vimentin CD34, MIC2 (cytoplasmic) and Bcl-2, while cytokeratin (CK), epithelial membrane antigen (EMA), calretinin, HBME-1 (meso), S100 protein, smooth muscle actin (SMA) and desmin were negative [Figure 3]a-e, [Figure 4]. Diagnosis of a SFTP was offered. Section of adjacent lung (parenchymal cut margin) was free of tumor. In view of its large tumor size and focal areas of atypia with mitoses, a close follow-up was suggested.
|Figure 3: Histopathological findings. (a) Patt ernless proliferation of spindly cells separated by thick bands of keloid-like collagen and perivascular hyalinizati on (upper left corner). H and E ×100. (b) Focal areas|
of diff use hyalinizati on. H and E ×100. (c) Higher magnifi cati on showing bland spindly cells with vesicular chromatin amidst sclerotic stroma. H and E ×400. (d) Focal areas of hypercellularity exhibiti ng mild to modeate nuclear pleomorphism with mitosis (arrow). H and E ×400.
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|Figure 4: Immuohistochemical fi ndings (IHC). (a) Tumor cells exhibiting diffuse vimentin positivity. DAB ×200. (b) Diff use positi vity for CD34. DAB ×200. (c) Cytoplasmic positivity for MIC2/CD99. DAB ×200. (d) BCL-2 positi vity in the tumor cells. DAB ×200.|
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| Discussion|| |
Solitary fibrous tumor of the pleura forms less than 5% of all pleural neoplasms, with limited documentation of the cases, in contrast to the more common mesothelioma at this location. ,,,, Two-thirds of these tumors arise from the visceral pleura and one-third from parietal pleura. 
The clinical presentation of SFTP varies according to its size and location. In early stages, it is often asymptomatic but can grow to enormous size, causing chest pain, dyspnea and cough. Its average T-size is 6-8 cm.  We present here an uncommon, giant SFTP measuring 25 cm that led to cough and chest pain in an elderly patient. Paraneoplastic syndromes such as hypoglycemia, digital clubbing and hypertrophic pulmonary osteoarthropathy are also noted, especially in a large-sized SFTP, but these were absent in the present case. ,,
Grossly, multinodularity of the excised mass led to consideration of mesothelioma less likely, as it is generally a diffuse mass. Histopathologically, in view of spindly cells, the differential diagnoses included a desmoplastic spindle cell mesothelioma; a monophasic synovial sarcoma; fibromatosis, a leiomyoma; a malignant peripheral nerve sheath tumor (MPNST); a fibrosarcoma and a malignant fibrous histiocytoma. A spindle cell mesothelioma shows fascicular or a haphazard distribution of the tumor cells and the desmoplastic type shows abundant collagen that was seen in our case. However, the tumor cells are positive for CK, calretinin and/or HBME-1 in a mesothelioma that were lacking in our case. A monophasic synovial sarcoma shows spindle cells arranged in a hemangiopericytomatous pattern with variable positivity for CK, EMA, Bcl-2, CD99 and vimentin; the latter three markers akin to a SFTP, as noted in our case. CD34 positivity ruled out a synovial sarcoma. Similarly, a fibromatosis, a malignant peripheral nerve sheath tumor (MPNST) and a fibrosarcoma were ruled out due to lack of their pathological features and aforementioned IHC profile. In this way, CD34 positivity with clinicopathological profile helped in confirming the diagnosis of a SFTP in our case.
The prognostic factors for a SFTP include T-size. Cases with T size of more than 10 cm are known to be associated with recurrences and metastasis. ,, At the same time, large-sized SFTP can be benign. ,, In our case, the T-size was 25 cm. Sessile tumors, as in the present case, in contrast to pedunculated tumors, have been found to be associated with high chances of recurrence. 4 Additionally, the tumor in our case was circumscribed, but not infiltrative, a feature that is associated with an aggressive course. A SFTP is considered malignant if it exhibits high cellularity, significant nuclear pleomorphism, necrosis and mitoses more than 4/10 hpf.  Our case showed focal hypercellularity and nuclear pleomorphism and mitoses less than 4/10 hpf, but there was no coagulative necrosis. The outcomes of large-sized SFTPs have been variable as enlisted [Table 1]. Low expression of progesterone receptors and CK positivity are associated with worst outcome that were both negative in our case.  Lately, liposarcomatous differentiation has been documented in a SFTP that was absent in the present case.  A SFTP is managed by a surgical excision, in contrast to a mesothelioma that includes adjuvant chemotherapy. The present case was recommended a follow-up, in view of its atypical findings.
|Table 1: Literature review of cases of an solitary fibrous tumor of the pleura more than 10 cm size, with outcomes|
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To conclude, a SFTP is a relatively uncommon tumor. CD34 positivity is necessary for its objective diagnosis, over its differentials. Whereas a mesothelioma and high-grade sarcomas are candidates for adjuvant chemotherapy, a SFTP is treated surgically. Features of malignancy should be looked for with extensive sampling, especially in large-sized tumors.
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Department of Pathology, 8th Floor, Annex Building, Tata Memorial Hospital, Dr. E. B. Road, Parel, Mumbai - 400 012
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4]