Pituitary Gland, Pituitary adenoma, sparsely granulated somatotroph type, LMWK stain

This is a case of a growth hormone (GH)-producing pituitary adenoma, with some patches of thyroid stimulating hormone (TSH) immuno-positivity. Somatotrophic pituitary adenomas are further divided into different subtypes: sparsely or densely granulated somatotrophs. This distinction is achieved with the low molecular weight keratin (LMWK) stain. In this case, numerous LMWK(+) peri-nuclear fibrous bodies are noted, in accord with the diagnosis of sparsely granulated subtype. In contrast, only occasional fibrous bodies are seen in the cases of densely granulated subtype.

This slide shows LMWK stain. See Related Content for H&E, GH and TSH.