Ovary, Mature cystic teratoma, with well differentiated neuroendocrine tumour ("carcinoid").

Mature cystic teratomas are the most common ovarian germ cell tumour. In rare cases, somatic-type tumours can arise within the mature elements, including well-differentiated neuroendocrine tumours resembling gastrointestinal-type carcinoids. The outcome is generally benign.

In this slide, within a background of mature teratoma, is a 0.5 cm nodule of nests and trabeculae of uniform cells with “salt and pepper” chromatin, and granular eosinophilic cytoplasm is present in the cyst wall. Mitotic count is