History: A 9.5 year old female, spayed, mixed breed dog with progressive paresis.
Gross Findings: Pituitary mass
Grossly the tumor appears hemorrhagic and more invasive than compressive but doesnt extend into very far into the thalamus.
Pituitary: The neoplastic cells are variable in size and shape but do occasionally form follicles with eosinophilic colloid (PAS positive). There were two main populations of cells visible by H&E. One type of cell had bright eosinophilic granules (ACTH positive). The other had pale eosinophilic cytoplasm and were only faintly ACTH positive. There were multifocal areas of hemorrhage and necrosis.
Histologically the tumor looks more compressive than invasive. The majority of tumor cells were ACTH negative, or only faintly positive, but there were areas that were strongly ACTH positve (see below)
The large pink area stained very positive for ACTH.
The adrenal cortices were 2x as large as the medulla, and there was one hyperplastic cortical nodule. We did not think these were significant changes. The tumor was mostly non-secreting chromophobe cells, but did have some nice ACTH producing cells.