Primary breast lymphoma (PBL) is a rare subtype of non-Hodgkin's lymphoma (NHL) with rapid progression and high risk of central nervous system metastasis. We have investigated 40 PBL patients retrospectively, and 16 of them were sequenced by a target panel of 112 genes related with lymphoma. Next-generation sequencing (NGS) identified 203 mutations spanning 35 genes and revealed seven potential protein-changing genes (PIM1, MYD88, DTX1, CD79B, KMT2D, TNFAIP3, and ITPKB) with high frequency, referring crucial roles in lymphomagenesis. Our result suggested that PIM1 mutation is correlated with the age and pathological type of PBL patients. Gene TNFAIP3 and KMT2D mutation is only related to the pathological type and primary site, respectively. These high-mutant genes detected in PBL indicated a tendency to shorten overall survival (OS) and progression-free survival (PFS), which may lead to poor prognosis. Furthermore, the nuclear factor kappa-B (NF-kappa B) pathway and related regulatory factors are essential for the development of targeted therapy as well.