From 1978 to 1997 we have experienced four cases of primary carcinoma of the appendix, which ac-counted for 0.7% of all resected colorectal carcinomas in our hospital. Of the four cases, three cases were male and one case was female with the average age of 56.7 years ranged from 38 to 68. The chief complaints of them included lower abdominal pain in two cases, or palpable abdominal mass in one case and asymptomatic in one case. They were diagnosed preoperatively as acute appendicitis, sigmoid-colon carcinoma, ovarian tumor, and rectal carcinoma respectively. In the asymptomatic case the appendiceal carcinoma was detected during an operation for the rectal carcinoma. The preoperative diagnosis of the primary carcinoma of the appendix was very difficult as these cases had demonstrated. Operative findings showed pseudomyxoma peri-tonei in one case and severe involvement to other organs in two cases. Histological diagnosis was mucinous cystadenocarcinoma in all cases. Two patients died of carcinoma.
Our experience suggests that primary carcinoma of the appendix should be considered as a probable differential diagnosis for the patient having lower abdominal pain or an abdominal tumor.