Histological and immunocytochemical examinations of the stromal reaction in carcinomas of the parotid gland. Analysis of 52 cases.

Fifty-two carcinomas of the parotid gland were analysed with regard to their stromal reaction. This phenomenon was studied concerning the localization, intensity, and cellular pattern. The plasma cells which were an integral component of the stromal reaction were marked with respect to the production of the different classes of immunoglobulins. This investigation was done using the indirect immunoperoxidase technique as indicated by Taylor (1978). The carcinomas were classified according to the WHO-classification. There were 21 carcinomas in a pleomorphic adenoma, 8 squamous cell carcinomas, 13 adenocarcinomas (8 adenocarcinomas and 5 cystadenocarcinomas), 4 adenoid cystic carcinomas, 3 salivary duct carcinomas, and 3 anaplastic carcinomas. The intensity of the plasmacellular infiltration was evaluated by a quantitative method. Four degrees of intensity were established. The study revealed the following facts: 1. The carcinomas in pleomorphic adenomas showed a stromal reaction in the periphery of the tumor, whereas the centre of the tumor was devoid of a remarkable reaction. The stromal reaction was intense in the case of the mucoepidermoid tumors and anaplastic carcinomas. 2. The squamous cell carcinomas showed a stromal reaction in the periphery as well as in the centre of the tumor. High-differentiated squamous cell carcinomas were accompanied by a stronger reaction of the stroma than less differentiated ones. 3. The less differentiated adenocarcinomas revealed a marked stromal reaction in the periphery and centre of the tumor, whereas the high differentiated cystadenocarcinomas showed scarcely a stromal reaction. 4. The adenoid cystic carcinomas and the salivary duct carcinomas showed only a poor stromal reaction which sometimes appeared to be focally concentrated. 5. The infiltration of the plasma cells was observed mainly in the periphery of the tumors. The plasma cells contained generally IgG and a smaller number was IgA positive. The occurrence of cytoplasmic IgM seemed to be negligible. 6. The parts of the parotid gland which were not affected by the tumor showed on obstructive parotitis. It was focally concentrated. This fact was interpreted as the consequence of the growth of the tumor, which hindered the flow of the parotid secretion. This finding and the presence of granulocytes in the region of tumor necroses were not regarded as a stromal reaction in the exact sense of the term. The demonstration of a typical stromal reaction in the neighbourhood of the tumors was interpreted as an immunological reaction of the host organism against possible tumor-associated antigens.