Type B lactic acidosis associated with malignancies is a rare but life‑threatening complication, particularly in hematological cancers but less commonly in solid tumors. The current study presents a rare case of type B lactic acidosis in a 59‑year‑old woman with metastatic cervical neuroendocrine carcinoma (NEC), a highly malignant and uncommon tumor. The patient exhibited severe symptoms, including significant ascites, tachycardia and hyperlactatemia, with lactate levels peaking at 11.2 mM. Despite initial symptomatic treatments such as fluid replacement and sodium bicarbonate therapy, the patient's condition continued to deteriorate. Based on the literature, chemotherapy is considered potentially the only effective treatment for malignancy‑associated lactic acidosis. Given the critical status and poor general condition of the patient, a reduced dose of intravenous etoposide (100 mg; days 1, 3 and 4) was administered. After the first dose, the patient developed tumor lysis syndrome (TLS), which was promptly managed with appropriate interventions. Following stabilization, etoposide treatment was continued on the third and fourth days. Subsequently, a delayed intraperitoneal infusion of carboplatin (300 mg; day 6) was administered. Post‑chemotherapy, lactate levels significantly decreased to 2.2 mM, and the patient's overall condition improved, leading to discharge. This case underscores the potential efficacy of using reduced doses of etoposide (100 mg on days 1, 3 and 4) and intraperitoneal carboplatin (300 mg on day 6) in managing malignancy‑associated lactic acidosis. It also highlights the importance of proactive management of TLS and other chemotherapy‑related complications, contributing valuable insights to the limited literature on this subject.

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