Parietal cell/oncocytic gastric carcinoma: systematic review and first-time assessment of HER2 status in two new cases.

Introduction: Parietal cell/oncocytic gastric carcinomas are very rare and various aspects of this group remain unclear. The human epithelial growth factor receptor 2 (HER2) status of these tumours is largely unknown.

Methods: We performed a systematic electronic search of the literature and clinicopathological presentation of two cases including first-time complete assessment of HER2 status. Thirty-two patients with a mean age of 64.3 years, 87.5% of whom were male, were included in this review.

Findings: Half of the cases were recorded in Asia. Median follow-up was 24 months. There was no predominant site of development, while underlying histological abnormalities were present in 25%. At initial presentation, lymph node involvement was evident in 46.6% while distant metastatic disease was present in 9.3%. Presentation at stage I occurred in 55.6%. Potentially curative surgical/interventional treatment was intended in 90.6%. Recurrence occurred in 6.6%, while death was recorded in 19.2%, with cancer-related deaths reaching 11.5%. The one- and three-year survival rates were 84.2% and 79%, respectively. Our two cases displayed negative HER2 expression.

Conclusions: This systematic review demonstrates that this group of malignancies is very rare but possibly underdiagnosed. The disease commonly presents at early stage, mainly affecting middle-aged men. The prognosis is generally favourable even in cases of advanced disease. The HER2 expression and its correlation with the outcomes need to be further explored.