p27(kip1) and other cell-cycle protein expression in normal and neoplasticendocrine tissues

Endocrine tumors are often diagnostic challenges. Recent studies have sugge sted that proteins that regulate cell cycle may have diagnostic and prognos tic utility in endocrine tumors, p27(kip1) (p27) is a cyclin-dependent kina se inhibitor that regulates the transition from the G1 to the S phase of th e cell cycle, p27 and other cell-cycle proteins are becoming increasingly i mportant in assessing the biologic behavior of endocrine neoplasms, classif ying hyperplastic and neoplastic endocrine tissues, and in the progression of endocrine tumors. p27 appears to separate normal from neoplastic endocri ne tissues and, in some cases, benign from malignant endocrine tumors. Howe ver, there is overlap in p27 expression among individual cases of benign an d malignant tumors, and p27 has only limited prognostic utility in endocrin e tumors compared to some epithelial tumors such as breast and prostate neo plasms. Thus, more effective molecular and cellular markers that can be use d for diagnostic and prognostic purposes in endocrine pathology are needed.