Infiltrating plcomorphic lobular careinoma is a recently recognized, aggressive variant of lobular carcinoma that has the invasive pattern of classical infiltrating lobular carcinoma but that also has large plcomorphic nuclei and abundant cosinophilic, slightly granular cytoplasm. The authors described an infiltrating pleomorphic lobular carcinoma accompanied by an extensivein situcarcinoma that involved lobular units primarily. Thein situcarcinoma was cytologically identical to the infiltrating carcinoma and was interpreted as thein situcounterpart of infiltrating pleomorphic lobular carcinoma.