478 Primary Squamous Cell Carcinoma Arising in a Transplanted Kidney

Introduction/Objective Primary squamous cell carcinoma (SCC) of the kidney is a rare malignancy, and its occurrence in a transplanted kidney is exceedingly uncommon. Kidney transplantation is the preferred treatment for end-stage renal disease, but post-transplant patients remain at increased risk of malignancies due to long-term immunosuppression. While cutaneous malignancies are most frequently encountered, primary renal tumors in the allograft, including renal cell carcinoma and urothelial neoplasms, are rare. Here, we report a case of primary SCC arising in a renal allograft. Methods/Case Report A 62-year-old male with history of end-stage renal disease due to IgA nephropathy, underwent a deceased donor kidney transplant. Patient denies any prior history of malignancies. His post-transplant course was notable for persistently elevated creatinine and borderline T-cell–mediated rejection, requiring intensified immunosuppression. One year after transplantation, a renal ultrasound revealed a 6.4 × 7.6 × 6.4 cm lobular, heterogeneous mass in the medial aspect of the transplanted kidney. Biopsy of the renal mass demonstrated moderately differentiated, keratinizing squamous cell carcinoma. Immunohistochemical staining showed diffuse positivity for p63 in tumor cells. PET imaging revealed hypermetabolic lymphadenopathy (left supraclavicular, mediastinal, retroperitoneal) and pulmonary nodules, consistent with metastases. A cervical lymph node biopsy demonstrated morphology similar to the renal tumor, supporting metastatic spread from the primary kidney lesion. The patient began chemotherapy and dialysis; nephrectomy was not pursued due to widespread disease and extensive fibrosis, which posed surgical challenges. Results NA Conclusion This case illustrates an exceptionally rare presentation of primary SCC in a renal allograft, with early metastasis. Studies indicate that malignancies identified within two years post-transplant are more likely to originate from the allograft, supporting our interpretation, while those diagnosed beyond two years are typically considered metastatic in origin. Chronic inflammation and prolonged immunosuppression are key predisposing factors. Early recognition, biopsy, and imaging correlation are essential for managing rare post-transplant malignancies effectively.