p130 expression in thyroid neoplasms: its linkage with tumor size and dedifferentiation

p130 belongs to the retinoblastoma-related gene family, and its gene product works to negatively regulate cell cycle progression in the G1 phase. In this study, we investigated p130 expression in thyroid neoplasms. p130 overexpression was observed in 33.3% of follicular adenoma and 50% of follicular carcinoma and the incidences were not significantly different. In papillary carcinoma, it was overexpressed in 36.5% of cases, but in microcarcinoma, the incidence was significantly lower (14.3%). Furthermore, in anapalstic carcinoma, p130 overexpression was less frequently seen than in papillary carcinoma except for microcarcinoma and follicular carcinoma, and only 14.3% of cases overexpressed this protein. These findings suggest that: (1) reduced p130 expression may contribute to the aggressive character of anplastic carcinoma; and (2) p130 may specify the growth characteristics of microcarcinoma.