In conclusion, we found that 28% and 6% of SBAs, mainly sporadic or CrD-related, expressed CLDN18 in ≥1% (of any intensity) and ≥75% (score 2+/3+) of tumour cells, respectively, suggesting that CLDN18 may be a potential therapeutic target even in a fraction of SBAs, and that MUC5AC+/CK7+ SBAs harbour the highest probability to exhibit immunoreactivity for CLDN18. The gene discussed is MUC5AC; the disease is neoplasm.