Apoptotic index from fine needle aspiration cytology as a criterion to predict histologic grade of non-Hodgkin's lymphoma

OBJECTIVE: To investigate whether the assessment of apoptotic index (AI) fr om needle aspirations (FNA) smears of non-Hodgkin's lymphomas (NHL) is reli able and has potential utility as a criterion to predict histologic grade. STUDY DESIGN: AI was independently determined by four cytopathologists by f our cytopathologists as a percentage from routine FNA smears in 96 NHLs and 15 lymphoid hyperplasias. Working formulation (WF) grades from correspondi ng surgical biopsies were modified to include mantle zone-derived NHLs as i ntermediate grade and to make diffuse large cell NHL a separate category ca lled "high" grade, whereas WF high grade NHLs were called "very high" grade . Histologic grade were also derived from the Revised European American Lym phoma (REAL) classification. AI was compared with histologic grade using th e unpaired, two-tailed Student t test. These data were used to determine po tential thresholds for AI that separate lower from higher grade NHLs. RESULTS: Measurements of AI strongly correlated between cytopathologists (m edian r=.93). Low and intermediate grade NHLs had indistinguishable AIs, wh ereas higher grade NHLs had significantly higher AIs. Appropriate potential AI thresholds between low or intermediate grade and higher grade NHLs were in the range of 1.5-2.5% (modified WF) and 1-2% (REAL).