An Ultrastructural Study on Muciparous Microcysts of the Human Adenohypophysis

Abstract

The microcysts found in two adenohypophyses removed from patients with nonsecreting adenomas of this gland have been studied. In one case the cysts were completely surrounded by neoplastic tissue, whereas in the second they were located within the normal parenchyma. The cysts were surrounded by a basement membrane, and appeared to contain a finely granular weakly electron-dense substance. Their walls were lined by mostly cubic cells with microvilli, joined by junctional complexes. Intracytoplasmic microlumina could be seen in some of these cells. Cells showing cilia with a 9 + 2 fibrillar pattern and cells with mucosecretory differentiation were also present. Furthermore endocrine cells were also found in the cyst-lining epithelium. The ultrastructural aspects of the cyst cells lead to reject the hypothesis that these are derived from folliculostellate cells. Besides, intermediate aspects between cyst cells and tumor cells were never visible. Therefore it seems likely that a relationship between adenoma and cyst cells does not exist and that cyst cells originate from remnants of Rathke’s pouch with a ciliate or mucosecretory differentiation. The presence of endocrine cells in the cyst-lining epithelium deserves further study, for it seems to indicate that an endocrine differentiation may occur in the adult, too. To our knowledge this is the first ultrastructural study of these structures in adult human pituitary gland.

Pituitary adenoma with rich folliculo‐stellate cells and mucin‐producing epithelia arising in a 2‐year‐old girl

“…Follicle or microcyst formation by FSC has been described in pituitary adenoma, 1 and FSC have been observed to directly join the surrounding adenoma cells by adherent junction ultrastructurally 12 . Some mucin granules, in several cases, have been found forming microcysts in FSC, which is a similar feature to that of Rathke's cyst‐lining cells 8,13 . The present case is very unique in that there were rich FSC and an abrupt transition between the FSC and the mucin‐producing glandular epithelia, resembling goblet cells.…”

Primary Cilia in Normal and Pathological Tissues

“…The question as to whether cilium expression alters during the rapid proliferation cycles following ma lignant transformation has been adressed. but it is already known that a wide variety of tumours possess cells with primary cilia, from adenocarcinomas of the pituitary [35] to Brenner's tumour of the ovary [36], However, Wilson and McWhorter [37] had written some time ago that 'among the basal cell carcinoma flagella (primary cilia) seem to be the most common in the least aggressive tumors'. 228 Wheatley Primary Cilia and Cell Pathology …”