DNA ANALYSIS AND S-PHASE FRACTION DETERMINATION BY FLOW CYTOMETRIC ANALYSIS OF INFILTRATING LOBULAR CARCINOMA OF THE BREAST

Flow cytometric analysis was performed on 50 infiltrating lobular carc inomas (ILCs) of the breast from 50 patients with clinical follow-up ( average duration, 4.1 yr) who had been treated between 1976 and 1991. The patients were classified as alive with no evidence of disease, ali ve with disease, or dead of disease. Ploidy and S-phase fraction (SPF) were compared with clinical outcome, histologic pattern (classical ve rsus variant patterns), nuclear grade 1 or 2, axillary lymph node stat us, tumor size, percentage of signet ring cells, and estrogen receptor status. There was no association between aneuploid or diploid ILC and disease recurrence (of those patients classified as alive with no evi dence of disease plus dead of disease, 4 (40%) of 10 were aneuploid an d 15 (38%) of 40 were diploid), survival (of those classified as alive with no evidence of disease plus alive with disease, 9 (90%) of 10 we re aneuploid and 36 (90%) of 40 were diploid), or any of the other fac tors evaluated. However, ILCs with a high SPF were more likely to recu r than those with a low SPF (a high SPF was found in 9 [56%] of 16; a low SPF was found in 9 [30%] of 30), but this relationship was not sta tistically significant (P = 0.08). When only diploid ILCs were conside red, there was a statistically significant association between high SP F and recurrence (a high SPF was found in 9 [64%] of 14, a low SPF was found in 6 [24%] of 25, P = 0.033), After the stratification of the d iploid ILCs by the stage of disease, this relationship persisted only in Stage 1 (recurrence: a high SPF was found in 3 [75%] of 4; a low SP F was found in 1 [9%] of 11, P = 0.033). There was no association betw een SPF and any of the other factors evaluated, Our study indicates th at ILC is usually diploid and that SPF may be a prognostic indicator t hat is limited to Stage 1 disease.