MUC5AC and carcinoma: Based upon a common expression of neuroendocrine markers in the carcinoma cells of diffuse gastric cancer [51,52,53,71,72], and that the PAS positive material in the signet ring cell carcinomas, a subgroup of carcinomas of diffuse type, is not mucin [55], we have argued that the gastric carcinomas of diffuse type actually are NE tumours [49,53,56].