A newly proposed semi-automated method of grading invasive lobular carcinoma: a unifying concept and correlation with prognostic markers and patient survival.

Invasive ductal carcinoma (IDC) of the breast is currently graded according to the Nottingham modification of the Scarff-Bloom-Richardson system (SBR). This system involves subjective evaluation of 3 morphologic features: tubule formation, nuclear pleomorphism, and mitosis. Our recently proposed semi-automated Nuclear and Proliferation Index [N+P] grading system for IDC has demonstrated agreement among grades and prognostic markers with better prediction of patient survival than the SBR system. Our present objective is to expand the utilization of the N+P system to grading invasive lobular carcinoma (ILC). Fifty-eight ILC cases were evaluated by the SBR and N+P systems. The 2 systems were compared in terms of correlation with patient survival, tumor size, grade, angiolymphatic invasion, lymph node status, ploidy status, and ER, PR, Her-2, p53, EGFR, and Bcl-2 staining. The N+P and SBR systems demonstrated overall agreement when correlated with clinical and prognostic parameters. Twenty-four of 30 tumors initially classified as SBR Grade II were down-graded to N+P I. Three of 26 tumors initially classified as SBR Grade I were up-graded to N+P II. Grading of ILC provides valuable predictive and prognostic information. The N+P grading system for ILC decreases the element of subjectivity for assessing mitotic activity and appears to be superior to the SBR system in predicting patient survival.