A Clinicopathological and Immunohistochemical Study of Pleomorphic Adenoma

Pleomorphic adenoma occurring in the oral cavity is neoplastic salivary gland tumor originating from the major and minor salivary glands and has the most frequent rate of occurrence among salivary gland tumors. Although this tumor is said to be benign clinically, it presents various structures, and recurrence and malignancy occasionally occur. Many reports therefore have been made on this tumor as a disease of interest. However, there are still many matters yet to be clarified such as correlation between clinical symptoms and histopathological structures, histogenesis, and hitological types. A sufficient grasp of this tumor has not yet been attained. A clinicopathological and immunohistochemical investigation therefore was performed to elucidate these matters. The results were as follows : 1. In histopathological types of the 32 cases of pleomorphic adenoma, cellular type was most frequent with 15 cases (46.9%), followed by simple type with 10 cases (31.3%), and adenomatous type with 7 cases (21.9%). 2. As to histological types and sites of occurrence, simple type and cellular type occurred more at the palatal mucosa and adenomatous type at the palatal mucosa or buccal mucosa in many cases. 3. Regarding histological types and age of occurrence, simple type occurred in ages from thirties to sixties, adenomatous type in forties, and cellular type in fifties in many cases. 4. Although no differences were seen between histological types and tumor sizes, cellular type was seen in relatively larger tumors in many cases. In histological types and tumor hardness, simple type was elastic soft and adenomatous type was elastic hard, in many cases. 5. In histopathological structure of the 32 cases, chondroid pattern accounted for 18 cases (56.3%), myxomatous pattern 15 cases (46.9%), and cartilage pattern 10 cases (31.3%). Squamous cell metaplasia was seen in 8 cases (25.0%). Recurrence was seen in 3 (9.4%) of the 32 cases and findings of myxomatous pattern were found in the 3 cases. Capsule was incomplete. In treatment of this tumor, therefore, enough care must be given to presence or absence of formation of capsule and of extracapsular infiltration as well as histological types and histopathological structure, and surgical extirpation as wide as possible is desirable. 6. In histochemical investigation of this tumor, Periodic Acid Schiff (PAS) stain showed positive reactions at the portions of squamous cell metaplasia, myxomatous pattern, and cartilage pattern. Mucicarmin (MC) stain and Alucian-Blue (AB) stain showed positive reactions at the portion of myxomatous pattern. 7. In immunohistochemical investigation of this tumor, S-100 protein reacted negatively to normal myoepithelial cells and positively to tumorous myoepithelial cells and cartilaginous myoepithelial cells. Carcinoembryonic antigen (CEA) reacted positively to tumorous cells showing squamous cell metaplasia. Furthermore, localization of Keratin (KER) was suggestive of differentiation tendency toward squamous epithelia of tumorous myoepitherial cells. On the basis of the foregoing investigation results, it was suggested that epithelial cell of the intercalated duct is the histogenesis of pleomorphic adenoma.