Abstract
The human thymuses, the well differentiated carcinoma, the thymoma with spindle epithelial cells and the undifferentiated thymoma have been examined by histochemical techniques [lactate dehydrogenase (LDH), succinate dehydrogenase (SDH), acid phosphatase (AcP), alkaline phosphatase (ALP) and dihydrofolate dehydrogenase (DHFR)] to study the metabolic changes due to the pathological conditions in the epithelial cells (EPCs) and accessory cells. In all three different types of studied thymomas the EPCs showed a more intense LDH and SDH positivity than in normal thymus. These data indicate a possible damage of respiratory chain energy-coupling mechanism. The EPCs presented a different pattern (negative or very strong) of ALP and AcP positivity both in normal and pathological thymuses. These results suggest that the EPCs are a heterogenous population presenting a variety of functional activities both in normal and pathological conditions. The macrophages showed a different pattern (very weak, weak and moderate) in dehydrogenase and in hydrolytic enzymes both in normal and tumour cells. The macrophages were uniformly distributed throughout the thymoma but it is interesting to note that in the well differentiated thymomas these cells were localized in high number only around the neoplastic nodules that were proliferating. These findings suggest that the macrophages are important for defending the organism against the formation of new neoplastic nodules.
