Would you offer adjuvant abemaciclib plus endocrine therapy for favorable histology ER+/PR+/HER2-negative tumors such as pure tubular, mucinous, cribriform, or papillary that otherwise meet MonarchE trial criteria?   

These pure subtypes are rare (<5%) and many pathology studies state that the term should be reserved for cases where at least 90% of the tumor is tubular or mucinous with low grade features to be considered favorable. In one retrospective study for over 100 G1 pure tubulars, only 5% had N1 diseas...

I would discuss it with the patient. Abemaciclib is not easy to tolerate and I would counsel them on the potential side effects. But yes, I would offer it to the patient since patients irrespective of histology/Ki67 were included in the monarchE trial if they had several positive LNs/larger tumor si...