NODULAR FOCI IN PARATHYROID ADENOMAS AND HYPERPLASIAS - AN IMMUNOHISTOCHEMICAL ANALYSIS OF PROLIFERATIVE ACTIVITY

Samples of normal, hyperplastic, and neoplastic parathyroid tissues we re analyzed for proliferative activity to determine (1) whether a high er number of proliferating cells were detectable in adenoma and hyperp lasia versus normal tissues; (2) whether there was a difference in the number of proliferating cells in adenoma versus hyperplasia; and (3) whether there was a relationship between nodularity and proliferative rate in both adenoma and hyperplasia. Formalin-fixed, paraffin-embedde d tissue from 21 patients with parathyroid adenoma and 10 patients wit h hyperplasia (two primary, six secondary, and two tertiary) was analy zed by immunohistochemistry with the monoclonal antibody PC10 to proli ferating cell nuclear antigen (PCNA) and, in a subset of cases, with K i-67 (MIB 1) as markers of cell proliferation. The results were that ( 1) no proliferating cells were found in normal glands or residual rim of ''suppressed'' parathyroid tissue; (2) the most intense proliferati ve activity was confined to nodular areas in both adenomas (57% nodula r) and hyperplasias (80% nodular); (3) when fields of highest number o f labeled nuclei were chosen, PCNA counts were higher in adenomas than in hyperplasias in both nodular and diffuse areas (P < .05); and (4) the number of nuclei immunoreactive for Ki-67 (MIB-1) was consistently and proportionally lower (range, 13% to 45%; mean, 32%) than the numb er of those immunoreactive for PCNA, although the nodular pattern was maintained. These findings demonstrate that nodules within parathyroid adenomas and hyperplasias contain subpopulations of cells with a cons istently higher proliferative rate than nonnodular areas. Cells within these nodules may be more likely to develop genetic abnormalities tha t have been observed in hyperplastic and neoplastic parathyroid tissue s. Copyright (C) 1994 by W.B. Saunders Company