Clinical observation of the total 685 cases of mucous cyst was reported, of which, histological examination was performed for 291 cases and the amino acid compositions of the cyst contents was analyzed for 9 cases.
1. Out of 685 cases, 425 cases could be diagnosed as mucoceles and 260 cases ranulas.
2. Seventy-nine per cent of the mucoceles were located in the lower lip, 11 per cent in the tongue and 8 per cent in the buccal mucosa. Most of the ranulas were located in the mouth floor.
3. Mucous cysts were most frequently found in the third decade of patient age. Ratio of female to male patient was 2.8 in ranula and approximately one in mucocele.
4. The amino acid compositions of the cyst contents of ranula were similar to that of serum, and differed from that of submaxillary-sublingual saliva.
5. Direct communication between the cyst and the salivary gland were found in all the 26 cases of mucous cyst examined in serial section.
6. Five of 26 cases examined were ranula, and were classified as extravasation cyst. It was found that some of them were communicating to sublingual glands with multiple ducts. There was squamous metaplasia of the torn end of these ducts.