Contributed by Fabio Rogerio, MD, PhD; Joăo Vitor Gerdulli Tamanini; Gunter Gerson, MD; Thiago Costa Haiter; Luciano de Souza Queiroz, MD, PhD; Mateus Dal Fabbro, MD
FINAL DIAGNOSIS
Pituitary gangliocytoma associated with acromegaly.
DISCUSSION
Pituitary gangliocytomas are uncommon tumors constituted almost exclusively by neoplastic ganglion-like cells. Even though these tumors tend to affect females more than males, their extreme rarity precludes evaluation of age distribution. The clinical syndrome more commonly associated with pituitary gangliocytomas is acromegaly. Unusual presentations with hyperprolactinemia, precocious puberty or Cushing disease have also been described, as well as association with adenoma, either as isolated or mixed components (6, 8, 9).
The main pathological finding in pituitary gangliocytomas is morphologically abnormal, haphazardly distributed neurons in a neuropil-like background. The cells often exhibit peripheral Nissl bodies, cytoplasmic vacuolation and multinucleation. Glial cells are virtually non-demonstrable (2, 8). Lesions clinically associated with endocrine syndromes may have hormones detectable by immunohistochemistry in the ganglion cells, or these may be produced by occasionally associated adenomas. Also described are a few cases of acromegaly in which the ganglion cells were immunopositive for GH-releasing hormone (GRH) (3, 7).
As for histogenesis of gangliocytomas, it is debatable whether adenohypophysial cells would transform into neuronal cells, or, conversely, a ganglion cell neoplasm would induce adenohypophysial hyperplasia or adenoma. Further, a common stimulus could induce neoplastic transformation of both epithelial and neuronal cell lineages (2, 9).
In the present case, neoplastic neurons frequently showed rounded, isolated cytoplasmic inclusions strongly positive for cytokeratins (AE1AE3). Similar structures in pituitary adenoma cells have been named fibrous bodies (5). The occurrence of such structures in the pituitary gangliocytoma that we report may suggest that the two lineages namely neuronal and adenomatous are related. However, in spite of the clinical finding of acromegaly, there was no evidence of a concomitant pituitary adenoma in our case. Thus, we may hypothesize that (i) gangliocytoma was the only tumor present; (ii) an adenoma may have existed but was not included in the surgical specimen or (iii) may have fully differentiated into gangliocytoma (2, 4, 6, 10). Moreover, a remarkable finding was that the so-called fibrous bodies reacting for cytokeratins were also marked for GFAP, even though they occurred in the cytoplasm of neoplastic neurons. It is a common finding that cross reaction between intermediate filaments of different categories may occur, possibly through similarities of some epitopes, a finding that may also depend on the particular antibody being tested. In this context, cross reaction between GFAP and cytokeratins has been demonstrated in human gliomas (1).
REFERENCES
Contributed by Fabio Rogerio, MD, PhD; Joăo Vitor Gerdulli Tamanini; Gunter Gerson, MD; Thiago Costa Haiter; Luciano de Souza Queiroz, MD, PhD; Mateus Dal Fabbro, MD
International Society of Neuropathology