Radio/ Oncol 1996: 30: 268-70.
Sarcomatoid carcinoma of the thymus - a case report
Nan-Yung Hsu1, Chih-Yi Chen1, Po-Chung Kwang2, Chung-Ping Hsu1,
and Jiun-Yi Hsia1
'Division of Thoracic Surgery, 'Department of Surgery, 2Department of Pathology, Taichung Veterans General Hospital, Taichung, Taiwan, Republic of China
A 20-yea/'-ol// /emale with a .swc'omalo/V/ cn/'cinomn o/ ihe /hymus i/nWi/ig the leji upper' lobe c/' the lung was Ireale// with su/'gica/ re.sec/iun and a^i^/uvant /'ad/uthe/'apv. We /'epu/7 c/ cave «/' /his rare histologic va/'iant u/' thymic: cpareino//;a and review the li/eratu/'e.
Key wo/d/s: thymu.s neoplasms; carcinosarcoma; .sarcomatoid carcinoma.
Introduction
Sarcomatoid carcinoma of the thymus is a rare histologic variant of thymic carcinoma. which was named by Snover et al in 1982.1 That group also suggested that a thymic carcinoma should fulfill the following criteria: ( 1) anterior mediastinal location and (2) absence of another primary tumor. We have reported 20 consecutive cases of thymic carcinoma in a 10-year period at our institute.' Among these 20 cases. no histologic variant of sarcomatoid carcinoma has been disclosed. We hereby describe a case od sarcomatoid carcinoma of the thymus that, microscopically, contains both a malignant epithelial component and a sarcomatoid component. The expression of cytokeratins and epithelial membrane antigen (EMA) in tumor cells could differentiate it from true sarcomas which do not stain for these markers.'
Case report
A 20 year old female presented with a six month history of increasing dyspnoea and lcft chest pain.
Correspondence lo: N.Y. Hsu. M.D. Division of Thoracic Surgery, Depl. of Surgery, Taichung Veterans General Hospital, No. 160, .Section 3. Taichung-Kang Road. Taichung. Taiwan, Republic of China.
UDC: 616.438-006.68
On admission. physical examination revealed decreased breath sounds in her left upper chest. No lymphadenopathy was found. The full blood count revealed a haemoglobin of 13.7 g/dl, a white celi count of 7.8 x 10"/1 (neutrophils 7.2, eosinophils 0.2, lymphocyte 1.7), and a platelet count of 371 x 1071. A chest radiograph demonstrated a big mass in the anterior aspect of the lelt lung. A computed tomographic (CT) scan of the chest showed a big necrotic tumour, measuring 14 x 12 x 12 cm in size. arising from the anterior mediastinum and invading to the left upper lung field (Figure 1). The serum titre of beta-choriogonadotropin (beta-HCG), alfa feto proteim (AFP) and carcinoembrionic antigen
Figure J. CT scan of the chest demonstrating a big mass arising from the anterior mediastinum and invading the left upper lung field.
Sarcomatoid carcinoma of the thymus — a case report
269
(CEA) were within normal limit. Sono-guided aspiration of the tumour was performed, and a cytologi-cal examination showed spindle celi tumour. 99m Tc-MDP whole body bone scanning and liver sonography showed no evidence of metastatic foci.
An operation was performed via standard posterolateral thoracotomy. While the tumour occupied the whole anterior mediastinum. ils left laterai sile invaded the lefl upper lobe of the lung. Removal of the mediastinal tumour with a left upper lobectomy of lung was performed. The postoperative course was uneventful, and the intercostal drain was removed on the fifth postoperative day.
Histopathological examination of the tumour revealed a custers of epithelial cells mixed with the strap-like spindle cells (Figure 2). An irnmunohis-tochemical study showed a positive staining for cytokeratin in the epithelial area and in some spindle cells (Figure 3). The patient then received radiotherapy with a 6000 Gy tumour dose. There was

Figure 2. Cliisler ofthymic epithelial cells mixed with straplike spindle cells (hernatoxylin-eosin. x400).
Figure 3. Sarcomaloid carcinoma of the thymus slum 111» dark colouration in Ihe epithelial area and in some spindle cell s (peroxidase-antiperoxidase [PAP] staining with cylo-keratin) (original magnification x400).
subjective improvement of dyspnoea and chest pain, and the palienl is currently alive I O months after surgery with no evidence of tumour recurrencc or melastasis.
Discussion
Thymic carcinoma per se is a relatively rare tumour. with distinct pathological and clinical characteristics. There were eight histological variants of thymic carcinoma, reported in the literatures with sarcomatoid type among them.1, 4 Various tumours showing the histological features of sarcomatoid carcinoma are seen also in other organs such as: lung/ pancreas.'' kidney,7 breast." and urinary bladder.9 However. sarcomatoid carcinoma of the thymus, as one of the histological variant of thymic carcinoma, has seldom been reported. The clinico-pathologic features of the reported cases are summarized in Table 1. Clinically. this tumour mostly occurs in middle or in old age. similarly to the other variants of thymic carcinoma. To our knowledge. this is the youngest case reported in the literature.
In our previous study of 20 cases of thymic carcinoma, we found that invasion of the mediastinal stuctures is almost always present, including the inominate vein, mediastinal pleura, perieardium, and lung.2 As compared with thymoma, thymic carcinoma has a more invasive tendency on computed tomographic scan examinations, and most of the patients have clinical symptoms caused by tumour compression of the mediastinal vital structures.2- s
In general. thymic carcinoma are immunoreac-tive to EMA and cytokeralin, but not reaetive to AFP, beta-HCG, placental alkaline phosphatase. or common leukocyte antigens.11-13 Snover et al suggest that the presence of keratin within the spindle celi component can justify the use of the term "sarcomatoid carcinoma".2
In one case, initially, germ celi tumour was highly suspected, bul a subsequent study of a series of tumour markers disclosed no elevation serum titre of beta-HCG, AFP and CEA.
During operation, we found that the space-occupied mediastinal tumour invaded the left upper lobe of the lung. but fortunately, the hilar struetures such as the left upper lobar bronchus, superior pulmonary vein, and pulmonary artery branches to left upper lobe of lung were pushed laterally by the tumour, and lotal removal of the tumour with a lobectomy could be performed without difficulty.
270
Hsu NYet al.
Table l. Reported cases of sarcomatoid carcinoma of the thymus.
Year/Author	Age/Sex	Symptoms	Location/Size/Invasion	Therapy	Follow-up
1982/Snover et al1""- '	64/M	Asymptoms	Ant. mediastinal/	Excision	died with
			6x5x4.4 cm/-		metastasis at 13 months postop.
1982/Wick et al"''"	53/M	Chest pain, dysphagia, SVC syndrome	Ant. mediastinum/?/SVC	RT&CT	died with metastasis at 28 months postop.
1992/Morita et al""'-10	53/M	Asymptoms	Ant. mediastinum/?	Excision	?
			lung, pericardium		
1996/Hsu et al	2()/F	Chest pain,	Ant. mediastinum/	Excision +	alive IO months
		dyspnoea	l4xl2xl2 cm/ lung	RT	postop.
SVC - superior vena cava. RT - radiotherapy, CT - chemotherapy
There is still a limited experience in the management of thymic carcinoma. Complete resection of these tumours is sometimes difficult because of the presence of invasion of the mediastinal structures. However. surgical resection should be attempled whenever possible to decrease the tumour burden. The role of postoperative irradiation in the treatment of sarcomatoid carcinoma of the thymus is unknown because of limited experience in this field. In our previous study of thymic carcinoma, we showed that pathological stage, type of resection, postoperative radiotherapy, and celi type did not indicate a significantly favorable result.2
We presented a 20-year-old patient with a giant tumour, biphasic histology and with evident disease after surgery. She was believed to be at high risk of recurrence. Hopefully, complete resection and adjuvant radiotherapy in this patients can lead to a more favorable outcome.
Reference
1.	Snover DC, Levine GD. Rosai J. Thymic carcinoma: five distinctive histological variants. Am .1 Surg Pathol 1982; 6(5): 4.51-70.
2.	Hsu CP. Chen CY. Chen CL, Lin CT. Hsu NY, Wang JH, Wang PY. Thymic carcinoma: ten years' experience in twenty patients. .1 Thorac Cardiovasc Surg 1994; 107: 615-20.
3.	Ogawa K, Kirn YC, Nakashima Y. Yamabe H, Takeda T. Hamashima Y. Expression of epithelial markers in sarcomatoid carcinoma: an immunohistochemical study. Histopathology 1987: 11: 511-22.
4.	Wick MR, Scheithauer BW. Weiland LH, Bernatz PE. Primary thymic carcinomas. Am .1 Surg Pathol 1982: 6(7): 613-30.
5.	Nappi O, Glasner SD, Swanson PE, Wick MR. Biphasic and monophasic sarcomatoid carcinomas of the lung. A reappraisal of 'arcinosarcomas' and 'spindle-cell carsinomas'. Am .1 Cliii Patho/ 1994; 102(3): 331-40.
6.	Alguacil-Garcia A, Weiland LH. The histologic spectrum, prognosis, and histogenesis of the sarcomatoid carcinoma of the pancreas. Cancer 1977; 39(3): 1181 —9.
7.	Bertoni F, Ferri C, Benati A, Bacchini P. Corrado F. Sarcomatoid carcinoma of the kidney. .1 Urol 1987; 137(1): 25—8.
8.	Meis JM, Ordonez NG, Gallager HS. Sarcomatoid carcinoma of the breast: an immunohistochemical study of six cases. Virchows Arch 1987; 410(5): 415—21.
9.	Torenbeek B, Blomjous CE, de Bruin PC, Newling DW, Meijer CJ. Sarcomatoid carcinoma of the urinary bladder. Clinicopathologic analysis of 18 cases with immunohistochemical and electron microscopic findings. A111.1 Surg Pathol 1994; 18(3): 241—9.
10.	Morita M. Kakimoto S, Isoda K, Sasaki S, Takeuchi A. A case of thymic carcinoma, sarcomatoid type (in japanese). Kyobu-Geka 1992; 45(4): 371—4.
11.	Battifora H, Sun TT, Bahu RM. Roa S. The use of antikeratin anlisurum as a diagnostic tool: thymoma versus lymphoma. Hum Patlwl 1984; 11: 635—41.
12.	Sloane JP, Ormerod MG. Distribution of epithelial membrane antigen in normal and neoplastic tissues and its value in diagnostic tumor pathology. Cancer l 981; 47: 1786—95.
13.	Fukai IF, Masaoka A, Hashimoto T, Yamakawa Y. Mizuno T. Tanamura O. Cytokeratins in normal thymus and thymic epithelial tumors. Cancer 1993; 71: 99—105.