AN ATYPICAL ACIDOPHIL CELL-LINE TUMOR SHOWING FOCAL DIFFERENTIATION TOWARD BOTH GROWTH-HORMONE AND PROLACTIN CELLS

We report a case of giant pituitary adenoma in a child. Computerized t omography (CT) scan revealed a suprasellar extension tumor mass with h ydrocephalus. There was no clinical evidence of acromegaly, gigantism, and other hormonal symptoms. Endocrinologic studies showed with in no rmal value of serum growth hormone (GH: 4.2 ng/m L) and slightly incre ased levels of prolactin (PRL: 78 ng/mL) and other pituitary hormone v alues were within normal range. On suppression test by bromocryptin, b oth GH and PRL levels were reduced. Histopathological findings reveale d that the tumor consisted of predominantly chromophobic and partly eo sinophilic adenoma cells. Immunohistochemical staining detected GH and PRL in a small number of distinctly different adenoma cells, respecti vely. Nonradioactive in situ hybridization (ISH) also showed GH and PR L mRNA expression in identical immunopositive cells. Electron microsco py (EM) demonstrated adenoma cells with moderate or small numbers of t wo types of dense granules and without fibrous body which are characte ristic of sparsely granulated GH-cell adenomas. The adenoma does not f it into any classification but may be an atypical acidophil cell line tumor showing focal differentiation toward both GH and PRL cells.