A 75-year-old woman was diagnosed with symptomatic IgG-l multiple myeloma (good-prognosis group) in December 2010. A stringent complete response (sCR) was achieved by using induction therapy with bortezomib (BOR, Velcade®)+ dexamethasone (DEX)(VD) and consolidation therapy with BOR+lenalidomide (LEN, Revlimid®)+DEX(VRD). Although maintenance therapy with Revlimid®+DEX(Rd) was initiated, a pancreatic neuroendocrine tumor was detected in April 2013. Therefore, LEN was discontinued and distal pancreatectomy was performed in September 2013. Because discontinuation of LEN was followed by exacerbation of myeloma, LEN was resumed with the consent of the patient; however, she became resistant to the treatment. The course of this case suggests that some patients must continue to receive LEN even if a sCR is achieved.