Infiltrating lobular carcinoma (ILC) of the classic type is well recognized; less well appreciated is a group of variant forms of ILC, which includes solid, alveolar, mixed, apocrine, signet-ring, histiocytoid, and tubulolobular variants. In addition, Page et al (Diagnostic Histopathology of the Breast, Churchill Livingstone, 1987, pp 219-226) recently have emphasized the pleomorphic variant of ILC, which demonstrates the infiltrating pattern of classic ILC; however, the nuclei are more pleomorphic and have features that may overlap with those of infiltrating duct carcinoma. To determine whether pleomorphic ILC shows significant prognostic differences from classic ILC, we reviewed the clinical courses of 25 patients with classic ILC and compared them with 16 patients with pleomorphic ILC. The major determinant in placing ILC into the pleomorphic category was the presence of nuclei of nuclear grade 2 or 3. All classic ILCs had nuclei of grade 1 by the Scarff-Bloom-Richardson criteria. Survival to recurrence was significantly worse (P less than or equal to .05) for the patients with pleomorphic ILC at lengths of survival greater than 30 months. In addition, node-negative patients with pleomorphic ILC were four times more likely to experience recurrence than node-negative patients with classic ILC; those with positive nodes and pleomorphic histology were 30 times more likely to experience recurrence. Although there appeared to be a trend toward decreased overall length of survival for those patients with pleomorphic ILC when compared with patients with classic ILC, this difference was not statistically significant.