Liposarcoma

Background.-Primary liposarcomas of the pleura are extremely rare malignancies, and relatively few reports appear in the world literature.

Design.-We compiled a small series of 4 cases of primary pleural liposarcoma from the files of the Armed Forces Institute of Pathology (Washington, DC) and compared the histopathologic and clinical features of these 4 cases with those of 9 previously published cases.

Results.-Our investigation included the case studies of 9 men and 4 women, aged 19 to 80 years (average, 49 years). Histologic subtypes in the 9 cases with available information included 5 myxoid liposarcomas, 1 well-differentiated liposarcoma, and 3 liposarcomas with mixtures of histologic types. Surgical resection with or without chemotherapy appeared to be the most common form of treatment, although radiation therapy was used in some cases and seemed beneficial. Survival information was available for 11 cases; 4 patients died of disease at 7, 9, 12, and 19

months; 1 died of heart failure 2 days after presentation; 1 died of unknown causes 16 months after presentation; and 3 patients were alive without tumor at 5, 16, and 66 months after diagnosis. One patient had local recurrence at 2 years. A second surgical resection in this patient failed, and he died of disease 9 years after initial presentation. A second patient experienced recurrence at 4 years and was free of disease 4 years after the second surgical resection.

Conclusions.-Primary pleural liposarcomas occur predominantly in older men, and the myxoid histologic subtype is the most common. Radiographic or surgical evaluation is important to distinguish primary pleural liposarcoma from chest wall or mediastinal sarcomas, as well as metastases from other sites. Although further investigation is needed, evidence from the cases reviewed here indicates that surgical resection with adjuvant radiation therapy may benefit patients with primary pleural liposarcoma.

(Arch Pathol Lab Med. 2000;124:699-703)

Sarcomas arising in the pleural cavity are rare. However, most of the histologic types have been described in this location, including synovial sarcoma, malignant fibrous histiocytoma, primitive neuroectodermal tumor/ Ewing sarcoma, angiosarcoma, chondrosarcoma, osteosarcoma, and leiomyosarcoma. Liposarcoma is among the most common soft tissue sarcomas, ranging in incidence from 9.8% to 16%.1 Liposarcoma most commonly arises in the retroperitoneum or thigh, but can also involve numerous other anatomic sites, such as the inguinal area, popliteal fossa, buttock, shoulder, arm, neck, back, and scalp, as well as the genitourinary and aerodigestive tracts.' Liposarcomas of the mediastinum and chest wall have been documented by other investigators; however, primary pleural liposarcoma is very rare and only a few isolated cases have been reported.27 We present herein the clinical and pathologic features of 4 previously unreported cases of pleural liposarcoma and compare our findings with those of 9 previously reported cases.

MATERIALS AND METHODS

Four cases of pleural liposarcoma were retrieved from the files of the Armed Forces Institute of Pathology (AFIP), Washington, DC. The histopathology was reviewed, and clinical parameters with follow-up data were obtained. The tumors were classified histologically according to the AFIP criteria proposed by Enzinger and Weiss.' Radiographic and operative data were reviewed to determine if the tumors had any involvement of the chest wall or mediastinum on initial presentation.

The clinical and pathologic features of our 4 cases were summarized and compared with those of previously reported pleural liposarcomas.

RESULTS

Clinical Features

Our series included 3 men and 1 woman, aged 45 to 80 years (average, 66 years). The clinical features of these cases are summarized in the Table. In all cases, radiographic or operative findings localized the tumors to the pleura and revealed no chest wall or mediastinal involvement at the time of initial presentation.

Case 1 involved a 45-year-old white woman who presented with symptoms of bronchitis and pneumonia. Work-up revealed a 16 X 16 X 4-cm mass located in the pleural cavity. The mass was surgically excised; however, tumor involved the margins of resection. The patient subsequently received chemotherapy consisting of adriamycin, vincristine, and etoposide. The pathologic diagnosis was myxoid and round cell liposarcoma. The patient died of disease 7 months after diagnosis.

Case 2 involved a 73-year-old white man who was found to have an incidental right pleural effusion on routine chest radiograph. Thoracoscopy revealed transparent, yellow, nodular lesions on the right pleura. A biopsy revealed a pathologic diagnosis of myxoid liposarcoma. The patient received only palliative care following the diagnosis. He died of disease 9 months after the initial diagnosis.

Case 3 involved a 67-year-old man who was found to have an 18.5 x 12.5 x 5.0-cm mass located in the left pleural cavity. The mass was excised and was found to be a well-differentiated/ sclerosing liposarcoma. No postoperative therapeutic information was available on this patient. He died of unknown causes 16 months after diagnosis.

Case 4 involved an 80-year-old white man who was found to have a pleural-based, right lower lobe, 20 x 18 x 14-cm mass on routine chest radiography. The mass was surgically resected and pathologically diagnosed as myxoid liposarcoma. No follow-up information was available on this patient.

Gross Pathology

The tumors ranged in size from 16 cm up to 20 cm in greatest dimension. The tumors in cases 3 and 4 weighed 540 and 1686 g, respectively. The tumors were yellowgray, rubbery, nodular, and lobulated to gelatinous, viscous, and mucoid.

Microscopic Pathology

Our cases included 2 myxoid liposarcomas (cases 2 and 4), 1 myxoid liposarcoma with round cell features (case 1 ), and 1 well-differentiated / sclerosing liposarcoma (case 3). In one case, the overlying pleura showed a hyperplastic mesothelial proliferation (Figure 1 ).

Myxoid/Round Cell Liposarcoma (Figures 2-4).-The tumors in cases 1, 2, and 4 were composed of elongated, interconnected spindle cells with variably sized, hyperchromatic nuclei with a wispy to fibrillary pale- to lightstaining myxoid stroma. More cellular areas were composed of atypical, round, uniform cells with hyperchromatic and vesicular nuclei. Occasional cells contained vacuolated cytoplasm with eccentric placement or scalloping of nuclei (lipoblasts). In the tumor with the round cell component (case 1), a second distinct population of rounded to oval cells had hyperchromatic, somewhat indented nuclei and some cytoplasmic vacuoles (round cells). An extensive capillary network was present, and multiple mitotic figures were seen.

Well-Differentiated/Sclerosing Liposarcoma (Figures 5-6).-The tumor in case 3 was composed of mature-appearing adipose tissue with loose to densely packed and sclerotic intervening and dissecting fibrous tissue. Occasional lipoblasts had hyperchromatic multilobulated nuclei that were compressed and distorted by cytoplasmic vacuoles.

Immunohistochemistry and Histochemical Stains.Immunohistochemical stains were performed on case 1 (myxoid /round cell liposarcoma) to exclude a mesothelioma, carcinoma, or rhabdomyosarcoma. Tumor cells were positive for vimentin (Boehringer-Mannheim Diagnostics, Indianapolis, Ind; 1:40) and negative for keratin (Boehringer-Mannheim; 1:2560), epithelial membrane antigen (Dako Corporation, Carpinteria, Calif; 1:100), desmin (Dako; 1:640), actin (Enzo Diagnostics Inc, Farmingdale, NY; 1:20480), and HMB-45 (Dako; 1:50). Staining for 5100 protein (Dako;1:2560) was equivocal. Alcian blue and acid mucopolysaccharide stains highlighted the myxoid background. Periodic acid-Schiff-positive, diastase-sensitive glycogen was present in some lipoblasts.

Review of the Literature

Including the 4 cases described herein, a total of 13 cases of primary pleural liposarcoma have been reported to date (Table). These cases included 9 men and 4 women, aged 19 to 80 years (average, 49 years). In the previously reported cases, cough, dyspnea on exertion, shortness of breath, and pleural effusion were the most common clinical presentations.z-5,s-lo Four patients died of disease between 7 and 19 months after initial presentation,5-8 including patients 1 and 2 of the current study. McGregor et all reported a case in which local relapse occurred at 2 years and subsequent death at 9 years following initial presentation. Wouters and Greve' described a patient with pleural liposarcoma in whom local relapse occurred 4 years after diagnosis, but additional surgery and radiation therapy rendered the patient disease free for 4 years. The patients described by Wong et al,4 Caroll et al,2 and D'Ambrosio and Hill6 were free of disease at 5 months, 16 months, and 66 months, respectively. Interestingly, 2 of these patients received radiation therapy.

Therapy in these patients generally consisted of surgical resection, radiation, or chemotherapy. Surgery was performed in most cases, while surgery with radiation was the most common combination therapy. In the 4 cases in which disease-free survival was accomplished,2,4,6,7 3 patients2,4,7 had received radiation therapy.

COMMENT

We have added 4 new pleural liposarcoma cases to the literature, thereby updating the review by Wong and colleagues 4 Our series, combined with the findings of their review, has found pleural liposarcomas to be male predominant with a median age at presentation of 50 years. Symptoms include chest pain, cough, and shortness of breath; on occasion, patients may be asymptomatic.

In other sites, liposarcoma is thought to be derived from residual rests of primitive mesenchymal tissue. Pleural liposarcoma likely arises in a similar manner. Lung embryogenesis begins as endodermal lung sacs derived from a diverticulum of the primitive esophageal ventral wall. Continued growth of the lungs leads to enlargement of the developing pleural cavity as the lungs expand. The pleural cavity forms from the mesoderm-derived chest wall, and its inner mesothelial lining is continuous with that of the pleura." During this complicated process, residual mesenchymal tissue rests that undergo malignant transformation later in life may conceivably develop, giving rise to pleural liposarcoma. Alternatively liposarcoma may develop from malignant transformation of a pre-existing lipoma, albeit rarely.1 Since there is mature fat in the submesothelial soft tissue of the parietal pleura and occasionally subpleural fatty metaplasia in fibrotic lungs, one may postulate liposarcoma of the pleura may develop if these tissues undergo malignant transformation.

Liposarcomas of the chest wall and mediastinum have been reported,12 and distinction from pleural liposarcoma with chest wall or mediastinal invasion requires careful radiographic evaluation, surgical evaluation, or both. In some cases it may be impossible to be certain where the tumor is arising. In our cases, the tumors appeared to be growing primarily within the pleural cavity, and chest wall or mediastinal involvement was minimal or absent. After recognizing the diagnostic histologic features of a liposarcoma, one must exclude the possibility of metastases or spread from either the chest wall or mediastinum. Other sarcomas that may be confused with liposarcoma include malignant fibrous histiocytoma, in which bizarre pleomorphic giant cells may be mistaken for pleomorphic liposarcoma. However, characteristic lipoblasts should be evident in liposarcoma. McGregor et a19 reported a case of well-differentiated and pleomorphic liposarcoma of the pleural cavity that recurred 2 years following excision; the histologic pattern of this tumor resembled malignant fibrous histiocytoma. Snover et al13 reported on 7 of 13 liposarcomas in which recurrences demonstrated a variety of histologic patterns, including malignant fibrous histiocytoma, malignant schwannoma, hemangiopericytoma, and unclassifiable sarcomas, as well as other liposarcoma subtypes. One might surmise that such patterns existed in the original tumors, thereby rendering them malignant mesenchymomas, or that the totipotential ability of the mesenchymal cells is retained even after differentiation along 1 tissue type. Krishna and Haqqani14 reported a case of malignant mesothelioma with liposarcomatous differentiation, although the pathologic documentation of this case was limited. The rarity of liposarcomas arising in the pleural cavity makes it difficult to identify prognostic factors that correlate with survival. The issue of surgical resectability is of paramount importance for patient survival, especially in low-grade sarcomas.lz Perry et a115 found that positive resection margins were an important prognosticator for chest wall sarcomas and that aggressive resection for high-grade chest wall sarcomas was warranted. Based on the small number of pleural liposarcomas reported to date, it is difficult to know if there is clinical importance to separating resectable pleural liposarcomas from chest wall sarcomas. Whether complete resection with adequate surgical margins improves survival for pleural liposarcomas needs further evaluation with a larger number of cases. Chemotherapy in one of our cases did not appear to be effective. However, of those reported cases in which radiation therapy was instituted, later onset of recurrence and longer disease-free survival were more likelv.2,4,7

Of importance to the pathologist is the histopathologic subtype of liposarcoma. The classification of liposarcoma is based on 5 histologic categories that generally reflect the degree of differentiation, ranging from well-differentiated liposarcoma to myxoid/round cell, dedifferentiated, and, finally, pleomorphic liposarcomas) Well-differentiated liposarcomas can be further subclassified as lipomalike, inflammatory, and sclerosing, based on features of similarity to lipomas, lymphoplasmacytic infiltrate, or areas of loose to dense fibrous stroma, respectively. Our cases, as well as those identified in the literature, demonstrate that the most common histologic subtypes of liposarcoma in the pleura appear to be myxoid and well differentiated. All forms of liposarcoma contain lipoblasts in varying numbers and morphologic forms; however, the more poorly differentiated liposarcomas behave more aggressively and can produce widespread metastases.

We have presented a series of 4 newly reported pleural liposarcomas and have summarized the clinical and pathologic features of 13 cases altogether, including 9 previously published reports. Clinical presentation may not immediately implicate pleural disease, or the discovery of pleural liposarcoma may be an incidental finding on routine chest radiographs. Our cases demonstrated histomorphologies similar to the histologic subtypes of liposarcomas recognized in other anatomic sites. As with liposarcomas from other sites, our less-differentiated cases (cases 1 and 2) behaved more aggressively and resulted in 7- and 9-month survival times, respectively, whereas the patient with the well-differentiated liposarcoma (case 3) survived 16 months. Based on information from these cases and previously published reports, it appears that patients with primary pleural liposarcoma may benefit most from surgical resection combined with radiation therapy.

References

1. Enzinger FM, Weiss SW. Soft Tissue Tumors. St. Louis, Mo: Mosby-Year Book; 1995.

2. Carroll F, Kramer MD, Acinapura AJ, et al. Pleural liposarcoma presenting with respiratory distress and suspected diaphragmatic hernia. Ann Thorac Surg. 1992;54:1212-1213.

3. Evans A, Wolstenholme R, Shettar S, Yogish H. Primary pleural liposarcoma. Thorax. 1985;40:554-SSS.

4. Wong WW, Pluth JR, Grado GL, Schild Sf, Sanderson DR. Liposarcoma of the pleura. Mayo Clin Proc. 1994;69:882-885.

S. Gupta RK, Paolini FA. Liposarcoma of the pleura: report of a case with a review of the literature and views on histogenesis. Am Rev Respir Dis. 1967;95: 298-304.

6. D'Ambrosio V, Hill M. First case of liposarcoma from the parietal pleura. / Med Soc N J. 1974;71:17-19.

7. Wouters EFM, Greve LH. Liposarcoma of the pleura. Neth J Surg. 1983;35: 192-193.

8. Ackerman LV, Wheeler F Liposarcoma. South Med J. 1942;35:156-159.

9. McGregor DH, Dixon AY, Moral L, Kanabe S. Liposarcoma of pleural cavity with recurrence as malignant fibrous histiocytoma. Ann Clin Lab Sci. 1987;17: 83-92.

10. Munk PL, Muller NL. Pleural liposarcoma: CT diagnosis. J Comput Assist Tomogr 1988;12:709-710.

11. Moore KL. The Developing Human Clinically Oriented Embryology. Philadelphia, Pa: WB Saunders; 1988.

12. Gordon MS, Hajdu SI, Bains MS, Burt ME. Soft tissue sarcomas of the chest wall: results of surgical resection. J Thorac Cardiovasc Surg. 1991;101:843-854. 13. Snover DC, Sumner HW, Dehner LP. Variability of histologic pattern in

recurrent soft tissue sarcomas originally diagnosed as liposarcoma. Cancer. 1982; 49:1005-101 S.

14. Krishna ), Haqqani M. Liposarcomatous differentiation in diffuse pleural mesothelioma. Thorax. 1993;48:409-410.

15. Perry RR, Venzon D, Roth )A, Pass HI. Survival after surgical resection for high-grade chest wall sarcomas. Ann Thorac Surg. 1990;49:363-369.

Accepted for publication October 12, 1999. From the Armed Forces Institute of Pathology, Department of Pulmonary & Mediastinal Pathology, Washington, DC. Reprints: William D. Travis, MD, Armed Forces Institute of Pathology, Department of Pulmonary & Mediastinal Pathology, 6825 16th St NW, Bldg 54, Room M003B, Washington, DC 20306-6000.

Copyright College of American Pathologists May 2000
Provided by ProQuest Information and Learning Company. All rights Reserved