Primary yolk sac tumor of the omentum: a case report and literature review.
Yolk sac tumor (YST) is a rare malignant tumor originating from germ cells. YST normally originates from the gonads, rarely occurring in extragonadal sites. We report a 35-year-old man with YST arising in the omentum, which is the first reported case of a primary YST of the omentum in an adult male. The patient presented to the community hospital with abdominal distension. A CT scan showed thickening of the omentum with ascites. The patient underwent open biopsy of the omental mass. The Pathology Department of the hospital could not make a definitive diagnosis at that time, and the tumor was considered a cancer of unknown primary (CUP) origin with features of primary colorectal cancer based on the immunohistochemistry (IHC) findings of the biopsy specimen (CK7-/CK20+ and CDX-2+). He was then referred to our hospital. We found that serum α-fetoprotein was abnormally elevated to 7,144 ng/ml (normal <10.0), and reevaluation of the biopsy specimen revealed microcystic or reticular patterns of tumor cells with Schiller-Duval bodies typical of YST. The present case suggests that IHC is a very useful diagnostic tool for subtyping CUP but should be interpreted in the context of clinical and morphological findings.
Breast and Medical Oncology Division, National Cancer Center Hospital, Tokyo, Japan.
Kenichi
K
Harano
Masashi
M
Ando
Yuko
Y
Sasajima
Mayu
M
Yunokawa
Kan
K
Yonemori
Chikako
C
Shimizu
Kenji
K
Tamura
Noriyuki
N
Katsumata
Hitoshi
H
Tsuda
Yasuhiro
Y
Fujiwara
Germ cell tumor; Immunohistochemistry; Omentum; Yolk sac tumor