A 50-year-old patient with a history of pancreas-kidney transplantation (2006), on triple immunosuppressant regimen with stable graft function, visited outpatient clinic presenting with symptoms of appetite loss, diarrhea, and a significant weight loss of 5 kg over 3 months. Subsequent upper and lower gastrointestinal endoscopies revealed various polypoid lesions of different sizes extending from the stomach to the colon. Tissue biopsies confirmed the diagnosis of monomorphic posttransplant lymphoproliferative disorder, Epstein-Barr-negative, diffuse large B Cell lymphoma. Furthermore, a 13 cm mass, suspected to originate from the right kidney, was detected on abdominal computed tomography (CT), along with multiple enlarged lymph nodes in the mesentery and retroperitoneum. Positron emission tomography (PET)-CT showed hypermetabolic lesions in the gastric body (maximum standardized uptake value [SUVmax], 6.6) and multiple hypermetabolic lymph nodes whole abdomen. Notably, the mass observed on CT in the right kidney showed an isometabolic profile on PET (SUVmax, 2.8). Ultrasonography-guided core needle biopsy of the right kidney mass revealed features consistent with oncocytic and clear cell neoplasm, favoring chromophobe renal cell carcinoma. The patient discontinued mycophenolate mofetil and underwent a radical nephrectomy, and permanent biopsy confirmed chromophobe renal cell carcinoma. After 1 month, the patient was scheduled of six cycles of R-CHOP chemotherapy. After received three cycles of R-CHOP chemotherapy, follow-up PET-CT and abdominal CT showed improved findings of multiple abdominal lymphadenopathy. Repeat GFS and CFS demonstrated the resolution of previously observed polypoid lesions with whitish scars. The patient’s digestive symptoms improved, and body weight increased by 5 kg compared to preoperative levels. This highlights the significance of both discerning posttransplant lymphoproliferative disease from other malignancies through diligent investigations and actively addressing coexisting disorders to improve patient outcomes.