title: Histologic characteristics of thymic adenocarcinomas: Clinicopathologic study of a nine-case series and a review of the literature.
abstract: Primary thymic adenocarcinoma is an extraordinarily rare malignancy; only 49 cases have been reported in the medical literature to date. Because of its rarity, clinical and pathologic characteristics of thymic adenocarcinoma are unclear. We present nine cases of primary thymic adenocarcinoma and discuss clinicopathologic findings in the context of the existing literature. Two-hundred twenty-six thymic carcinoma cases were diagnosed at Samsung Medical Center in Korea, from January, 2001 to July, 2016. Nine of these 226 cases were primary thymic adenocarcinomas. The mean age of primary thymic adenocarcinoma patients was 53.6 years, slightly younger than the mean age of patients with thymic squamous cell carcinomas. The male to female ratio was 2:1. Symptoms, if present, were usually due to compression by the tumor. Tumors showed an extra- or intra-cellular mucin and tubular growth pattern, with CK20- and CDX2-immunoreactivity, similar to adenocarcinomas of the lower intestinal tract. Twenty-five previously reported cases, classified as mucinous adenocarcinoma and adenocarcinoma, not otherwise specified, also had similar characteristics to enteric-type adenocarcinoma and generally expressed CK20, CDX2, CEA, and/or MUC2. Some of these cases had a thymic cyst. These characteristics are different from those of papillary thymic carcinomas, which are morphologically similar to papillary thyroid carcinomas, express CK7 but not CK20, and are often associated with thymoma. The prognosis of thymic adenocarcinoma, enteric type appeared to be worse than the prognosis of papillary thymic carcinoma or carcinoma with adenoid cystic carcinoma-like features. In summary, we demonstrated that common primary thymic adenocarcinomas show enteric-type differentiation with mucin. This tumor type has distinct clinical, pathological, immunohistochemical and prognostic characteristics and is different from other subtypes of thymic adenocarcinoma, papillary thymic carcinoma, and carcinoma with adenoid cystic carcinoma-like features.
authors.affiliation: Department of Pathology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
authors.forename: Ah-Young
authors.initials: AY
authors.lastname: Kwon
authors.affiliation: Department of Pathology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea. Electronic address: hanjho@skku.edu.
authors.forename: Joungho
authors.initials: J
authors.lastname: Han
authors.affiliation: Department of Pathology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
authors.forename: Jinah
authors.initials: J
authors.lastname: Chu
authors.affiliation: Department of Thoracic Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
authors.forename: Yong Soo
authors.initials: YS
authors.lastname: Choi
authors.affiliation: Department of Pulmonary and Critical Care Medicine, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
authors.forename: Byeong-Ho
authors.initials: BH
authors.lastname: Jeong
authors.affiliation: Department of Hematology and Oncology, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
authors.forename: Myung-Ju
authors.initials: MJ
authors.lastname: Ahn
authors.affiliation: Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
authors.forename: Yong Chan
authors.initials: YC
authors.lastname: Ahn
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism / Q000473:pathology*; D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000378:metabolism; D002272:Carcinoembryonic Antigen / Q000378:metabolism; D002294:Carcinoma, Squamous Cell / Q000378:metabolism / Q000473:pathology; D005260:Female; D006801:Humans; D007633:Keratins / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009077:Mucins / Q000378:metabolism; D013953:Thymus Neoplasms / Q000378:metabolism / Q000473:pathology*
chemical_list: D014408:Biomarkers, Tumor; D002272:Carcinoembryonic Antigen; D009077:Mucins; D007633:Keratins
keywords: Adenocarcinoma; Immunohistochemistry; Mucin; Subtype; Thymus