Clinicopathologic profiling of lung carcinoids with a Ki67 index greater than 20%

The clinicopathological features of lung neuroendocrine neoplasms (NEN) with a high proliferative index at the border area between atypical carcinoid and neuroendocrine carcinoma, have not been investigated so far. The aim of this study was, therefore, to search for lung NENs, which are well-differentiated but show Ki67 values that overlap with those of poorly differentiated NENs (PD-NENs). Resected lung NENs from 244 Japanese patients were reviewed and Ki67 index was assessed in all tumors. The data were then correlated to clinicopathological parameters and patient outcome. Among 59 (24%) well-differentiated NENs (WD-NENs) and 185 (76%) lung PD-NENs, seven were defined as WD-NENs with a Ki67 index>20%. The Ki67 index of these tumors (mean 29%, range 24-36) was significantly lower than that of PD-NENs (mean 74%, range 34-99). All WD-NENs with Ki67>20% lacked abnormal p53 and loss of Rb1 expression. In contrast, many PD-NENs expressed p53 (48%) and showed loss of Rb1 (85%). The 2- and 5-year disease free survival rates in WD-NEN Ki67>20% patients were lower than those of WD-NEN Ki67 ≤20% (p20% and those of PD-NEN. It is concluded that WD-NENs Ki67>20% share the morphological and immunohistochemical features with WD-NEN Ki67 ≤20%, but have a worse prognosis, suggesting that this tumor group has to be specifically considered in future classifications and probably need new therapeutic regimes.
Source: Neuroendocrinology - Category: Endocrinology Source Type: research