Apoptosis seems to be an important process in normal tissues and in neoplastic lesions. Although electron microscopic features of apoptosis are characteristic, it is difficult to detect apoptotic cells with accuracy by light microscopy. Labeling of intranucleosomal DNA fragmentation can provide information on the apoptotic status of
tumors. We studied apoptosis by the in situ end-labeling technique in 85
pituitary adenomas (63 functioning, 22 nonfunctioning). The functioning
tumors included 19 somatotroph, 17 lactotroph, 9 mixed
growth hormone/
prolactin-producing, 2 thyrotroph, and 16
corticotroph adenomas. A few scattered cells displaying characteristic apoptotic changes were observed by histologic examination and electron microscopy. We estimated the apoptotic labeling index (ALI) of the
adenomas by quantitating the percentages of positive nuclei. Overall, functioning
adenomas showed a significantly higher ALI (5.64%) than did nonfunctioning
tumors (1.84%). The ALI was higher in thyrotroph
adenomas (10.26%) and lower in corticotroph (5.94%), somatotroph (5.51%), lactotroph (5.25%), and mixed
growth hormone/
prolactin-producing
adenomas (5.11%). In conclusion, in situ end-labeling showed that apoptosis mostly occurs in functioning
pituitary adenomas. These data suggest that assessment of apoptosis can be used to evaluate
drug effects and to define which
adenoma subtypes are more susceptible to
drug therapy.