Krukenberg tumour of the ovary: a case report with light microscopy, immunohistochemistry and electron microscopy study.

A rare case of a 46-year-old woman with bilateral Krukenberg tumours is reported. Histologically, oedematous ovarian stroma was infiltrated by signet-ring cells arranged singly, in cords or in nests. Immunoreactivity for cytokeratin-7, carcinoembryonic antigen as well as histochemical positivity for mucins demonstrated the epithelial nature of the tumour. The gastric primary site was suggested by the cytoplasmic immunoreactivity for MUC-5AC and by ultrastructural evidence of gastric differentiation in signet-ring cells such as mucous granules with eccentric dense cores and intracellular microcysts, lined by sparse microvilli. Gastric biopsy, performed after pathological diagnosis, revealed a signet-ring cell carcinoma similar to that in the ovaries, confirming the gastric origin of the Krukenberg tumour. Because none of the individual immunohistochemical markers used for tissue identification is both site specific and site sensitive, electron microscopy in combination with immunohistochemistry is a valuable tool for the pathologist in the diagnosis of the tissue origin of a Krukenberg tumour.