抄録
Spontaneous invasive pituitary carcinoma of F344 rats used in a 2-year carcinogenicity study were examined histopathologically and immunohistochemically. A modified trimming procedure was devised to increase the detection rate of invasive tumors. The pituitary was dissected together with the sphenoid bone and surrounding tissues, and sagittal or transverse sections were made. The incidence of invasive pituitary tumors was 8.4% for males and 14.8% for females under these preparation methods. The neoplastic cells invaded the capsule, sphenoid bone, surrounding veins, pars intermedia and pars nervosa, peripheral nerve, meninges, and brain. In most of the cases, neoplastic cells infiltrated into the posterior portion of the pituitary capsule. From these observations, the tumor was diagnosed as carcinoma. The incidence of carcinoma invasion into the sphenoid bone was higher in males than in females. Similarly, the proliferating cell nuclear antigen (PCNA) labeling index of carcinomas in males was significantly higher than in females. Almost all carcinomas showed positive cytoplasmic reaction for prolactin (PRL) by immunohistochemical examination. Extra-cranial metastases were not found in these carcinomas. The present study demonstrates that histopathological examination of the pituitary tumor section including the surrounding tissues is crucial for making an actual diagnosis of neoplasm, and that spontaneous pituitary carcinomas in the rat resemble invasive pituitary tumor in humans.
