Small cell carcinoma of hypercalcemic type.

The small cell carcinoma of the ovary that is associated with paraendocrine hypercalcemia in two thirds of cases is characterized typically by poorly differentiated small cells with scanty cytoplasm, although larger cells with abundant cytoplasm are frequently observed as well, usually as a minor component of the tumor. The tumor almost always occurs in women in the second to fourth decade, usually presenting at a stage higher than stage 1A. It must be distinguished from other primary and metastatic small cell carcinomas that may involve the ovary. The tumor differs in its histologic, electron microscopic, immunohistochemical, and flow cytometric features from the pulmonary type of small cell carcinoma that may metastasize to the ovary from the lung and other organs or rarely may be primary in the ovary. The cell lineage of the small cell carcinoma remains a mystery. The tumor is highly malignant, with only a 30% survival rate in Stage 1A cases. It may be responsive to radiation therapy and combination chemotherapy, but long-term survival is rare once the tumor has spread beyond the ovary.