The t(11;14) (q13;q32) translocation resulting in overexpression of cyclin D1 is the major oncogenic mechanism in mantle cell lymphoma (MCL). Most MCLs can be diagnosed based on morphological features, cyclin D1 expression, and IGH/CCND1 rearrangement. However, in some atypical cases where conventional FISH studies fail to detect IGH/CCND1 rearrangement or immunohistochemistry for cyclin D1 is negative, the diagnosis of the disease can be difficult. Hence, next-generation sequencing (NGS) may allow the identification of molecular alterations and assist in the diagnosis of atypical MCL. In this study, we reported a case of a patient diagnosed as asymptomatic MCL who presented with lymphadenopathy during the initial assessment. A lymph node biopsy was performed and the results revealed a high Ki67 index. However, initial diagnosis of aggressive MCL was difficult since the IGH/CCND1 rearrangement result was negative. Ultimately, by the aid of NGS we identified a rare CCND3 rearrangement in the patient, which lead to overexpression of cyclin D3, thereby facilitating the diagnosis of MCL.