HER2-positive gastric cancer identified by serum HER2: A case report.
Immunohistochemistry (IHC) and fluorescencein situhybridization (FISH) are the current standards methods for the determination of tissue human epidermal growth factor receptor 2 (HER2) status in gastric cancer, as for breast cancer. However, HER2-positive gastric cancer occasionally exhibits heterogeneous tissue HER2 overexpression, raising concern regarding false-negative results in unresectable cases diagnosed by biopsy samples. Serum HER2, the concentration of the extracellular domain of HER2 protein shed into the bloodstream, has the potential to supplement the use of IHC or FISH to determine HER2 status. However, the clinical significance of serum HER2 has not been well studied in gastric cancer. The present study describes an illustrative case of metastatic gastric cancer initially diagnosed as HER2-negative (IHC score 1+). The patient exhibited an elevated serum HER2 level, which prompted a reevaluation of the tissue by IHC, using an alternative antibody, and FISH; re-biopsy analyses confirmed the case as HER2-positive, and trastuzumab was subsequently added to the combination chemotherapy with capecitabine and cisplatin. Serum HER2 may aid in avoiding false-negative diagnoses of HER2 gastric cancer.
Department of Gastroenterology, Rheumatology and Clinical Immunology, Sapporo Medical University, Sapporo, Hokkaido 060-8543, Japan.
Mayuko
M
Saito
Department of Gastroenterology, Rheumatology and Clinical Immunology, Sapporo Medical University, Sapporo, Hokkaido 060-8543, Japan.
Yujiro
Y
Kawakami
Department of Gastroenterology, Rheumatology and Clinical Immunology, Sapporo Medical University, Sapporo, Hokkaido 060-8543, Japan.
Kentaro
K
Yamashita
Department of Gastroenterology, Rheumatology and Clinical Immunology, Sapporo Medical University, Sapporo, Hokkaido 060-8543, Japan.
Hiroshi
H
Nasuno
Department of Gastroenterology, Rheumatology and Clinical Immunology, Sapporo Medical University, Sapporo, Hokkaido 060-8543, Japan.
Y U
YU
Ishimine
Department of Gastroenterology, Rheumatology and Clinical Immunology, Sapporo Medical University, Sapporo, Hokkaido 060-8543, Japan.
Koichiro
K
Fukuda
Department of Gastroenterology, Rheumatology and Clinical Immunology, Sapporo Medical University, Sapporo, Hokkaido 060-8543, Japan.
Hiroyuki
H
Isshiki
Department of Gastroenterology, Rheumatology and Clinical Immunology, Sapporo Medical University, Sapporo, Hokkaido 060-8543, Japan.
Ryo
R
Suzuki
Department of Gastroenterology, Rheumatology and Clinical Immunology, Sapporo Medical University, Sapporo, Hokkaido 060-8543, Japan.
Yoshiaki
Y
Arimura
Department of Gastroenterology, Rheumatology and Clinical Immunology, Sapporo Medical University, Sapporo, Hokkaido 060-8543, Japan.
Yasuhisa
Y
Shinomura
HER2 overexpression; false-negative; gastric cancer; intratumoral heterogeneity; sampling error; serum HER2