A 64-year-old woman (gravida 0, para 0) had a unilateral ovarian mass measuring 14 cm in its greatest diameter, which was mostly solid. Microscopically, the tumour was characterized by two predominant proliferating patterns: a carcinoid-like pattern with trabecular, tubular, glandular, or insular arrangements and a closely packed nesting pattern with central coagulation necrosis and occasional glandular arrangements. These two patterns were intermingled, and numerous mitotic figures were present. Electron microscopy showed neurosecretory granules in the cells, which were argyrophilic and positive for neuroendocrine markers (chromogranin, leu 7, neuron-specific enolase, and synaptophysin). The tumour was aneuploid by flow cytometry. The patient received chemotherapy postoperatively, developed brain and multiple bone metastases and died of disease 10 months after surgery. This tumour must be distinguished from other small cell neoplasms, especially ovarian small cell carcinoma of the hypercalcaemic type.