Calcitonin secreting struma-carcinoid tumor of the ovary.

The ultrastructure of strumal carcinoid tumors at times may reveal a far more complex structure than can be ascertained from light microscopy. It may at times be indistinguishable from medullary carcinoma of the thyroid gland. Both tumors appear to be capable of producing 5-hydroxyindolacetic acid and calcitonin. The common shared biologic and ultrastructural features suggest a common origin, from neuroectodermal cells.