Mucinous adenocarcinoma of the thymus: a distinct variant of thymic carcinoma.
BACKGROUND
Primary thymic mucinous adenocarcinoma is a recently described subtype of thymic carcinoma, which behaves aggressively.


METHODS
The authors analyzed the clinical and pathological findings of three cases of thymic mucinous adenocarcinoma, and reviewed five cases previously reported in the English literature.


RESULTS
The patients were two males and one female between the ages of 38 and 55 years. Macroscopically, the tumors were mostly solid and white to yellowish-white. Areas with a gelatinous appearance were present. Histologically, all of the tumors were adenocarcinomas with abundant mucin production, which resembled the mucinous adenocarcinomas of other organs. Malignant tumor cells in nests, tubules and cribriform structures floated in pools of extracellular mucin. In one case, associated thymic cysts were found at the periphery of the tumor. The cyst wall was partially lined by malignant mucinous epithelium, which showed transition from benign thymic epithelium. Immunohistochemically, all of the tumors showed positive immunoreactivity for cytokeratin (CK) 20 and carcinoembryonic antigen (CEA). CD5 was diffusely positive in one case, and focally positive in the other two cases. The prognoses of these cases were extremely poor, and two of the patients died within 24 months.


CONCLUSIONS
Growing evidence suggests that mucinous adenocarcinoma is a distinct morphological variant of primary thymic carcinoma. We believe that clinicians and surgical pathologists should include thymic mucinous adenocarcinoma in the differential diagnosis of mediastinal adenocarcinoma.
Maeda
Daichi
D
Department of Pathology, Mitsui Memorial Hospital, 1 Kandaizumicho Chiyodaku, Tokyo, Japan. maeda-tky@umin.ac.jp
Ota
Satoshi
S
Ikeda
Shingo
S
Kawano
Ryoji
R
Hata
Enjo
E
Nakajima
Jun
J
Mori
Masaya
M
Fukayama
Masashi
M
D002288:Adenocarcinoma, Mucinous / Q000378:metabolism / Q000473:pathology* / Q000628:therapy; D000328:Adult; D014408:Biomarkers, Tumor / Q000378:metabolism; D002272:Carcinoembryonic Antigen / Q000378:metabolism; D003131:Combined Modality Therapy; D003937:Diagnosis, Differential; D017809:Fatal Outcome; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D053554:Keratin-20 / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D013945:Thymoma / Q000378:metabolism / Q000473:pathology* / Q000628:therapy; D013953:Thymus Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000628:therapy; D014057:Tomography, X-Ray Computed
D014408:Biomarkers, Tumor; D002272:Carcinoembryonic Antigen; D053554:Keratin-20