✓ The authors report the case of a 40-year-old woman with a 12-year history of irregular menses, amenorrhea, infertility, galactorrhea, a slightly elevated prolactin level, and a slowly growing pituitary adenoma. She developed recent onset of visual symptoms, prompting craniotomy for removal of an intrasellar tumor. Following surgery, her vision and prolactin levels returned to normal.
Light microscopic and immunohistochemical examination of the tumor revealed it to be a neuroblastoma, which was immunohistochemically positive for synaptophysin, S-100 protein, and oxytocin. The neoplasm contained prolactin-positive neuroblastic and pituitary epithelial cells. No other pituitary hormones were found. Electron microscopy demonstrated two cell types: one with frequent neuritic processes containing neurosecretory granules and showing synaptic specialization, and another one compatible with epithelial adenohypophyseal cells. A few cells had ultra-structural features that were transitional between neuronal cells and granulated epithelial cells. Agranular folliculostellate cells were also identified. Immunoelectron microscopy demonstrated prolactin granules in the cytoplasm of the epithelial cells, in a few transitional cells, and in scattered neuritic processes.
Ultrastructural and immunohistochemical features of the tumor suggested a transformation of pituitary epithelium to neuroblastic cells. Hyperprolactinemia and associated clinical symptoms may in part be attributed to selective prolactin secretion by neoplastic cells that were differentiating into adenomatous pituitary cells and, to a lesser extent, to cells differentiating into a neuroblastic line. Compression of pituitary stalk might also have been a contributory factor to the increased prolactin levels. Moreover, the oxytocin produced by the neuroblastic cells was considered an additional stimulus for prolactin secretion by neoplastic cells or by the normal pituitary.