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Thymic carcinomas are uncommon malignant tumors, and thymic adenocarcinomas are extremely rare. Here, we describe a case of primary thymic adenocarcinoma in a 59-year-old woman. Histological examination of the tumor revealed tubular morphology with expression of cytokeratin 20 and caudal-type homeobox 2 according to immunohistochemistry, suggesting enteric features. Extensive clinical and radiological studies excluded the possibility of an extrathymic primary tumor. A review of the literature revealed only two global cases of primary tubular adenocarcinomas of the thymus with enteric immunophenotype.
Key Words: Thymus gland; Adenocarcinoma; Keratin-20; Caudal type homeobox 2
Thymic carcinomas are uncommon malignant tumors. According to the World Health Organization (WHO), thymic carcinomas are mostly squamous cell, lymphoepithelioma-like, or basaloid carcinomas.1 Thymic adenocarcinomas are extraordinarily rare. We herein report a case of primary thymic adenocarcinoma with tubular morphology and enteric immunophenotype as determined by expression of cytokeratin (CK) 20 and caudal type homeobox 2 (CDX2). The immunophenotype suggests metastasis from the gastrointestinal tract; however, extensive clinical evaluation revealed no extrathymic primary tumor. In addition, we review the literature to facilitate a discussion of the clinicopathologic characteristics of thymic adenocarcinoma.
CASE REPORT
A previously healthy 59-year-old woman presented with abdominal pain in the lower left quadrant that had persisted for 3 months. Endoscopic studies failed to reveal specific changes in the whole gastrointestinal tract mucosa. Imaging studies revealed an anterior mediastinal mass (Fig. 1A) and multiple lung nodules. Additionally, a whole-body positron emission tomography scan showed abnormal hyperuptake lesions in the left 10th rib and 10th vertebral body, suggesting metastasis (Fig. 1B). Laboratory tests indicated elevated levels of several serum tumor markers (carbohydrate antigen [CA] 19-9, 252.2 U/mL; CA125, 62.9 IU/mL; and carcinoembryonic antigen, 8.73 ng/mL).
The surgeon prioritized surgery for this patient not only because of her aggravated symptoms, but also because the tumor had invaded the left brachiocephalic vein. Approached through a median sternotomy, an extended thymectomy and combined resection of the pericardium were performed. Incomplete resection was inevitable because of tumor invasion into the pericardium, phrenic nerve, innominate vein, and aorta.
Gross examination identified a solid mass measuring 6.8 X 4.7 X 3.9 cm. The tumor was unencapsulated and invaded the pericardium. The mass was firm and rubbery with a homogeneous gray-whitish cut surface. There was no internal fibrous...