Folliculo-stellate cells of the human pituitary as adult stem cells: examples of their neoplastic potential.

Two unique, formerly unrecorded sellar neoplasms were observed in two women of 60 and 63 years of age. One lesion consisted of small epithelial cells and the other was a large-cell oncocytic tumor, yet they had the same simple cytoplasmic organization with dominance of polyribosomes and a sprinkle of glycogen. Striking markers shared by the neoplasms: (1) network of typical pituitary follicles, and (2) unexpected similarity to fetal human pituitary tissue at different gestational ages of 6 and 10-12 weeks. The latter showed appreciable endocrine differentiation. The assumed parent cell is the folliculo-stellate cell as pluripotent adult stem cell.

A double pituitary adenoma presenting as a prolactin-secreting tumor with partial response to medical therapy. Case report.

Double pituitary adenomas are difficult to recognize pre-operatively as only a single mass may be appreciated on imaging. We present herein a giant prolactin-secreting pituitary adenoma in a middle-aged man that had responded partially to dopamine agonist therapy. The excised specimen demonstrated a double adenoma. The prolactin-producing one displayed the expected morphological changes resulting from medical therapy, while the other, a gonadotroph adenoma, did not. The failure of tumor shrinkage can be attributed to the presence of a double adenoma, a previously unreported cause of failure of medical therapy in prolactinoma.

Cushing's Syndrome from an Ectopic Pituitary Adenoma with Peliosis: A Histological, Immunohistochemical, and Ultrastructural Study and Review of the Literature.

Ectopic pituitary adenoma (EPA) is rare and, to the authors' knowledge, its association with peliosis has not yet been described. The case of a 38-yr-old woman with clinical and biochemical evidence of Cushing's syndrome is reported. Magnetic resonance imaging (MRI) disclosed a normal pituitary and a separate mass in the sphenoid sinus. The surgically removed portion of the sellar pituitary contained no adenoma. There was only Crooke's hyaline change in the corticotrophs, indicating exposure to glucocorticoid excess. By histology, the mass in the sphenoid sinus was a congested, chromophobic, partly basophilic, periodic acid-Schiff (PAS)-positive pituitary adenoma composed of pleomorphic, adrenocorticotropic hormone (ACTH)-positive, corticotrophs. There was focal immunopositivity for MIB-1 and proliferating cell nuclear antigen (PCNA). Electron microscopy confirmed the diagnosis of corticotroph adenoma. A striking finding, consistent with the diagnosis of peliosis, was the presence of multiple large blood-filled spaces lacking an endothelial lining. The capillaries were dilated, but often appeared empty and the fenestrated endothelium exhibited discontinuities. The cause of peliosis is obscure. It may be that the venous outflow was impaired in this case leading to capillary dilation, congestion, hyperpermeability, rupture, and accumulation of blood in extravascular spaces.