We analyzed the frequency and anatomic distribution of atypical cystic lobules (ACLs) in patients whose index biopsy specimen contained lobular neoplasia (LN). Thirty of 54 patients (56%) had ACLs in their index biopsy specimen. Five of the patients whose index biopsy lacked ACLs underwent an additional biopsy, and 4 of these patients had ACLs in an additional specimen, bringing the total number of patients having both ACLs and LN to 34 of 54 (62.9%). ACLs involved both breasts with equal frequency and neither the extent of the involvement nor the anatomic location of the LN paralleled the distribution of the ACLs. The presence of ACLs in patients with LN might explain its increased risk for the development of ductal carcinomas and their bilateral distribution. Int J Surg Pathol 9(3):201-206, 2001