Primary B-cell lymphoma exhibiting a spindle dominant pattern is extremely rare and represents a potential diagnostic pitfall. Here we report two cases of extranodal B cell lymphoma with spindle cell dominant morphology (sp-BCL) of uterus and maxillary sinus. Case 1 was a 54-year-old female with a large mass in the lower uterine segment, inseparable from the wall of the rectum and the urinary bladder. This is the first report of primary sp-BCL arising in the lower uterine segment. Case 2 was a 54-year-old male with a permeative mass involving the maxillary sinus wall with extension into the premaxillary soft tissues. Biopsies of both cases revealed a diffuse infiltration by medium to large atypical spindle cells. A panel of immunohistochemical stains was performed to rule out the possibilities of sarcoma, carcinoma, or melanoma. The final diagnosis was diffuse large B cell lymphoma, germinal center type. This is the first report of sp-BCL incorporating molecular genetic studies and the next-generation sequencing analysis performed on the maxillary lymphoma revealed three genomic alterations in genes of EZH2 (Y646N), IRF8 (S55A), and TNFRSF14 (splice site 304+2T>C). These genes were reported to play important roles in the pathogenesis of diffuse large B cell lymphoma. Both patients achieved complete remission after excision and chemoradiation therapy despite the extensive local involvement.