Clinicopathologic characteristics of invasive lobular carcinoma of the breast - Results of an analysis of 530 cases from a single institution

BACKGROUND. Although invasive lobular carcinoma (ILC) is the second most common histotype of breast cancer, the prognostic implications of its clinicopathologic characteristics remain controversial. METHODS. The authors undertook a retrospective analysis of a large series of cases treated and followed at a single institution, with the objective of assessing the prognostic/predictive value of distinct clinicopathologic features of the tumors, after revision of the original histopathologic preparations and statistical analyses. RESULTS. Overall, 530 patients with pure ILC (57% with the classic type; 19% with the alveolar type; 11% with the solid type; and the remaining 13% characterized by pleomorphic, signet ring cell, histiocytoid, or apocrine features) were included in the study. Tumor size, lymph node metastatic involvement, and hormonal status were confirmed to be significant prognostic factors. In addition, statistically significant correlations were demonstrated between the 'classic' histotype of ILC and a lower risk of axillary lymph node metastases (P =.0005), a reduced number of metastatic lymph nodes (P =.04), and lower tumor grade (P <.0001). Patients with ILC of the 'nonclassic' subtype demonstrated significantly increased breast-related events (hazards ratio of 1.80; 95% confidence interval, 1.04-3.10) and a trend toward reduced disease-free survival and overall survival. CONCLUSIONS. The results of the current Study confirm the clinical usefulness of several traditional clinicopathologic features of ILC as prognostic parameters but also emphasize the prognostic role of the histopathologic subtyping of these tumors, documenting the more favorable outcome of the classic subtype of ILC.