It is rare for IgM multiple myeloma (MM) and mantle cell lymphoma (MCL) to coexist. Furthermore. it is challenging to demonstrate if there are two distinct types of neoplasia or if plasma cell differentiation of MCL is present. We discuss the case of a patient concomitantly diagnosed with MCL and IgM MM. https://www.adventuresonabike.com/product-category/lucidalabbra/