Figure 2.

Histological findings. A: a. Hematoxylin and eosin staining shows condensed tumor cells with pleomorphism, and depositions of osseous tissue are recognized. b. Vimentin was strongly positive. c. Anti-cytokeratin (CAM 5.2) staining is negative, indicative of no malignancy of squamous epithelium. d. Ki-67 scoring (MIB-1 index) is extremely high at 20%. B: The tumor tissue, resected from the patient 20 years ago, consists of typical pituitary adenoma cells, which are entirely different from the pathological features identified in A.