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Journal of Clinical Oncology, Vol 23, No 12 (April 20), 2005: pp. 2859-2861 © 2005 American Society of Clinical Oncology. DOI: 10.1200/JCO.2005.03.192
Unusual Thoracic Problems in Patients With MalignanciesCASE 3. Carcinoid Tumor of the ThymusDepartment of Radiation Oncology at the University of California, San Francisco
Department of Thoracic Surgery at the University of California, San Francisco
Department of Medical Oncology at the University of California, San Francisco A 37-year-old woman with a history of a resected well-differentiated papillary thyroid carcinoma presented for a routine follow-up examination and chest x-ray 10 months after her operation. She had a thyroidectomy for a multinodular goiter in September 2002 that incidentally revealed a 0.5-cm well-differentiated papillary thyroid carcinoma in the left lobe. The tumor did not have any lymphovascular space invasion, nor did it extend beyond the thyroid. However, it was present at the inked margin of the specimen. A chest x-ray at the time of surgery revealed no metastatic disease. The patient did well postoperatively, and she received no adjuvant therapy. She was asymptomatic and euthyroid on Synthroid replacement. Aside from a resection of a cervical cystic hygroma during her adolescence, her medical history was otherwise unremarkable. At her follow-up visit in July 2003, physical examination revealed a well-healed scar and no adenopathy or masses. The heart, lung, and abdominal examinations were all normal. However, the chest x-ray revealed a new mediastinal mass. Computed tomography (CT) of the chest revealed a 3 x 3 x 1.8-cm soft-tissue mass adjacent to the left pulmonary outflow tract (Fig 1). The patient subsequently underwent CT-guided fine-needle aspiration biopsy of the mass, which revealed a neoplasm growing in small nests and trabeculae. Immunohistochemical staining was positive for cytokeratin and synaptophysin, and was weakly positive for chromogranin. The tumor cells were negative for parathyroid hormone and S100. Together, the findings supported a diagnosis of carcinoid tumor. Twenty-four–hour urine metanephrines were in the normal range.
As the mass appeared resectable on CT, the patient underwent a left mini thoracotomy with complete en-bloc resection of the tumor. The resected mass measured 7 x 4.5 x 2.5-cm and weighed 14 g; it was surrounded by a fibrous capsule (Fig 2). Microscopically, the tumor cells were uniform, with coarse chromatin and scant to moderate amphophilic cytoplasm, typical of a carcinoid tumor. Mitotic figures were infrequent (Fig 3). Tumor cells invaded through the capsule into surrounding adipose tissue. Although the excision margins were negative, the closest approach was less than 1 mm. Lymphovascular space invasion was present within the tumor capsule and in the adjacent adipose tissue. Benign thymic tissue was present adjacent to the tumor. Immunohistochemical stains for synaptophysin and chromogranin were positive, confirming the diagnosis of carcinoid tumor of the thymus (Fig 4). A stain for calcitonin was negative, excluding medullary thyroid carcinoma. A postoperative CT scan revealed no evidence of residual tumor, nor any adenopathy or metastases in the neck or thorax.
Approximately 50% of carcinoid tumors are located in the gastrointestinal tract and up to one third occur in the lung and bronchus.1 These neoplasms are believed to arise from neuroendocrine cells, which are demonstrable in the normal thymus.1 Carcinoid tumor of the thymus, also referred to as thymic neuroendocrine carcinoma, was first reported in 1972.2,3 In this location the tumor is rare; approximately 200 cases have been reported in the literature to date.4 The age at diagnosis is variable and has ranged from 32 to 78 years among different case series.4,5 Men seem to be more frequently affected than women.4,6 Associations with other endocrine disorders have been reported. Both Cushing's syndrome (due to ectopic ACTH production) and multiple endocrine neoplasia syndrome type-1 have been associated with thymic carcinoid tumors.4,5,7 However, these neoplasms may also be endocrinologically silent as in the present case.4-6 Previously excised thyroid cancer (follicular, papillary, and medullary carcinoma) has also been reported among patients with carcinoid tumors of the thymus.5 Studies have demonstrated a clear clinicopathologic difference from thymoma.8 Carcinoid tumors have a more aggressive clinical course with local invasion of adjacent structures occurring in up to 80% of patients.5 Intrathoracic lymph node metastases occur in more than 40% of cases, and distant metastases, most frequently to the lung, bone, liver, and brain, occur in about one third.4,5 The behavior of thymic neuroectodermal tumors has been correlated with their histologic grade, with high-grade neuroendocrine carcinomas the most clinically aggressive.3 Surgical resection is the primary treatment of choice, but recurrence is common, and is detected in up to two thirds of patients. Despite extensive resection, even of encapsulated tumors, local-regional and distant recurrence is common.4,9 Consequently, postoperative radiation, chemotherapy, and/or chemoradiotherapy have been used with varying success among the different reports.4-8 According to one series, the major prognostic factor for survival was the extent of resection; postoperative radiotherapy seemed to prevent local recurrence.4 Because of the limited experience regarding treatment of these rare neoplasms, no definitive recommendations can be made regarding adjuvant therapy. However, because of the high risk of local-regional recurrence, this patient is currently receiving postoperative three-dimensional conformal radiation therapy to the preoperative tumor bed and the left hilar and mediastinal lymph node regions. Chemotherapy with a platinum agent and etoposide is planned following the completion of radiotherapy. Authors' Disclosures of Potential Conflicts of Interest The authors indicated no potential conflicts of interest.
REFERENCES 1. Modlin IM, Sandor A: An analysis of 8305 cases of carcinoid tumors. Cancer 79:813-829, 1997[CrossRef][Medline] 2. Rosai J, Higa E: Mediastinal endocrine neoplasm of probable thymic origin, related to carcinoid tumor: Clinicopathologic study of 8 cases. Cancer 29:1061-1074, 1972[CrossRef][Medline]
3. Moran C, Suster S: Neuroendocrine carcinomas (carcinoid tumor) of the thymus: A clinicopathologic analysis of 80 cases. Am J Clin Pathol 114:100-110, 2000
4. Tiffet O, Nicholson AG, Ladas G, et al: A clinicopathologic study of 12 neuroendocrine tumors arising in the thymus. Chest 124:141-146, 2003
5. Wang DY, Chang DB, Kuo SH, et al: Carcinoid tumours of the thymus. Thorax 49:357-360, 1994 6. Asbun HJ, Calabria RP, Calmes S, et al: Thymic carcinoid. Am Surg 57:442-445, 1991[Medline] 7. Teh BT, Zedenius J, Kytola S, et al: Thymic carcinoids in multiple endocrine neoplasia type 1. Ann Surg 228:99-105, 1998[CrossRef][Medline]
8. Kondo K, Monden Y: Therapy for thymic epithelial tumors: A clinical study of 1,320 patients from Japan. Ann Thorac Surg 76:878-885, 2003 9. Tamura M, Ohta Y, Oda M, et al: Thymic carcinoid tumor. Jpn J Thorac Cardiovasc Surg 51:29-31, 2003[CrossRef][Medline]
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Copyright © 2005 by the American Society of Clinical Oncology, Online ISSN: 1527-7755. Print ISSN: 0732-183X
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