Human epidermal growth factor receptor 2 overexpression in gastric and gastroesophageal junction adenocarcinoma in patients seen at the University Teaching Hospital, Lusaka, Zambia

Background: There are scanty data on the occurrence of gastric tumours overexpressing human epidermal growth factor receptor 2 (HER2) in Africa.
Objective: To assess HER2 protein overexpression in gastric and gastroesophageal junction adenocarcinoma (GGEAC) samples from a single centre in Zambia.
Methodology: This was a cross-sectional study of formalin-fixed paraffin-embedded blocks with GGEAC. Prepared slides were first stained with Haematoxylin and Eosin and then evaluated for HER2 protein overexpression by immunohistochemistry.
Results: A total of 57 gastric tissues were stained and evaluated for HER2 overexpression. Thirteen (23%) showed overexpression, 41/57 (72%) had negative and 3/57 (5%) had equivocal staining. The equivocal cases were excluded from the final analysis. Of the remaining 54 tissues, 28 (52%) were from females, and 26 (48%) were from males. The mean age was 59 years (SD 15 years). HER2 overexpression was highest in moderately differentiated tumours (p=0.0005). Intestinal type tumours had a higher occurrenc of HER2 overexpression than diffuse or mixed sub-types (p=0.0087). HER2 overexpression was not associated with age (p=0.27), sex (p=1.00) or anatomical location (p=1.00).
Conclusion: The occurrence of GGEAC HER2 overexpression in Zambian patients is similar to proportions reported elsewhere, and it is associated with moderately differentiated tumours of the intestinal type.

Keywords
Gastric and Gastroesophageal junction adenocarcinoma; Human Epidermal growth factor Receptor 2 overexpression; immunohistochemistry.