Objective: The association of tubular carcinoma, columnar cell lesions and lobular carcinoma in situ, also known as the “Rosen Triad”, may be encountered in breast biopsies performed for evaluation of mammographically detected microcalcifications.

Case Report: A case in which tubular carcinoma and columnar cell hyperplasia were associated with a histologically unusual form of signet ring lobular carcinoma in situ is presented. Signet ring non-invasive lobular carcinoma is classified as high-grade lobular carcinoma in situ, but herein is associated with changes that belong to the molecular pathway of low-grade mammary neoplasia.

Conclusion: We reported the case of lobular carcinoma in situ associated with columnar cell hyperplasia and tubular carcinoma, in which the lobular carcinoma in situ was presented in a histologically unexpected form comprised predominantly of signet ring cells.