Basaloid Urothelial Carcinoma Presenting With Paraneoplastic Hypercalcemia and Leukocytosis: A Case Report and Literature Review

BACKGROUND/AIM: Paraneoplastic syndromes rarely complicate the course of urothelial carcinoma. The simultaneous occurrence of two distinct paraneoplastic phenomena is an exceptionally rare event, often portending aggressive disease. CASE REPORT: We describe the case of a 49-year-old male tetraplegic patient with basaloid urothelial carcinoma that recurred as bulky nodal metastasis after radical cystectomy. The patient experienced a treatment-recalcitrant and aggressive clinical course complicated by persistent hypercalcemia and leukocytosis, which correlated directly with disease progression. Despite the challenges posed by the patient's quadriplegia, dedicated caregiving allowed the administration of three lines of systemic therapy. CONCLUSION: This case highlights the need to recognize the rare but clinically challenging co-existence of paraneoplastic hypercalcemia and leukocytosis in the setting of aggressive urothelial cancers. Our report contributes to the limited literature, exploring the putative mechanisms, including PTH-rP-independent hypercalcemia and G-CSF/GM-CSF secretion, and offers a clinical lesson regarding complex oncologic management in severely disabled patients.