Paraneoplastic cast nephropathy associated with malignant prolactinoma: A case report and literature review

Malignant prolactinomas are very rare and are diagnosed when a prolactin-producing pituitary adenoma has metastasized. We report on a 54-year-old man with a history of macroprolactinoma transforming into a pituitary carcinoma secreting both prolactin and growth hormone with metastases to the stomach, bone, lungs, retroperitoneum, and kidney. Reviewing the literature, this case is the first reporting of a pituitary carcinoma with biopsy-proven paraneoplastic cast nephropathy. Symptoms and renal function improved following a course of palliative chemotherapy and radiotherapy. After 2 years, his disease progressed requiring further palliative treatment that was complicated by severe chest sepsis. He was not fit for further chemotherapy, receiving symptomatic relief in a hospice, and died soon after. The case highlights the importance of considering a patient's past medical history in the context of persistent unexplained renal impairment and systemic metastases when unexplained systemic symptoms and multi-organ involvement is present. The importance of renal biopsy for definitive diagnosis and before using potentially nephrotoxic chemotherapy is also highlighted. Renal diagnosis helped inform the decision to give chemotherapy, with the importance of this evidenced by an improvement in renal function following chemotherapy.