Immunohistochemical properties of silent corticotroph adenoma and Cushing’s disease

Author： Iino Kazumi Oki Yutaka Matsushita Fumie Yamashita Miho Hayashi Chiga Miura Katsutoshi Nishizawa Shigeru Nakamura Hirotoshi

Publisher： Springer Publishing Company

ISSN： 1386-341X

Source： Pituitary, Vol.10, Iss.1, 2007-03, pp. : 35-45

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Abstract

Proopiomelanocortin processing in corticotroph cells is known to be operated by prohormone convertase (PC) 1/3 which is activating several proproteins and prohormones by intracellular limited proteolysis processing. In this study, we hypothesized that PC1/3 expression differs between Cushing’s disease (CD) and silent corticotroph adenoma (SCA), and investigated whether PC1/3 expression is involved in the adrenocorticotropin (ACTH) silence of SCA. We performed immunohistochemical analysis of pituitary adenoma specimens for six adenohypophysial hormones, PC1/3 and chromogranin A (CgA). Subjects for this study consisted of 12 anterior pituitary adenomas of CD (1 male, 11 female; 14–70 years old) and 31 non-functioning adenomas (23 male, 8 female; 32–71 years old).ACTH immunoreactivity was observed in all of CD and three of 31 non-functioning adenomas. The three cases diagnosed as SCA were also positive for growth hormone and follicle-stimulating hormone. Cushing’s adenomas and SCAs were all positive for PC1/3. PC1/3-positive cells did not always colocalize with ACTH but some of them colocalized with CgA in SCAs.Even if PC1/3 is not present in corticotroph cells, PC1/3 immunoreactivity in SCA may originate from CgA-positive cells. We conclude that immunohistochemistry for PC1/3 is not helpful for differential diagnosis between CD and SCA in clinical practice, though the regulation of PC1/3 expression is likely to be an important etiological factor in ACTH silence of SCA. The diversity of immunohistochemical properties of SCA leads us to speculate that it is not a single entity and may be a general diagnostic term for adenomas of varying etiology.