Prolactin cell carcinoma of the pituitary. Clinicopathologic, immunohistochemical, and ultrastructural study of a case with cranial and extracranial metastases

A patient with a primary adenohypophyseal neoplasm who had a long course marked by multiple surgical resections, radiation therapy, and high‐dose dopamine agonist therapy developed local invasion as well as cranial and extracranial osseous metastatic lesions. The serum prolactin levels were greatly elevated, and immunohistochemical studies demonstrated prolactin in the cytoplasm of primary and metastatic tumor cells. Ultrastructural features of lactotrophic differentiation, including misplaced granule exocytosis, were observed. This is the third reported case of prolactin cell carcinoma that metastasized despite high‐dose dopamine agonist therapy. Analysis of the patient's serum prolactin showed no abnormality in the chromatographic profile of biologic activity.