A diagnosis of primary endometrial diffuse large B-cell lymphoma was made on biopsy of posterior cervical mass that revealed diffuse infiltration of large lymphoid cells, positive for B-cell markers, namely, B-cell lymphoma 6 (BCL6), paired box 5 (PAX5+), CD20, and CD19 with methoxyisobutyl isonitrile (MIBI) of 100%, and negative for T-cell and mesenchymal markers, namely, CD3, CD45, CD43, CD138, Melan A, S100, and Vimentin. This evidence concerns the gene PAX5 and lymphoma.