A 50-year-old woman has a non-functioning 2 cm pituitary macroadenoma on MRI. She has no hormonal excess clinically. Histology shows chromophobic cells. Immunohistochemistry is positive for FSH and alpha-subunit, negative for prolactin, GH, ACTH, and TSH. Per WHO 2022 classification, this is best classified as a:

• A Gonadotroph adenoma ✓
• B Lactotroph adenoma
• C Somatotroph adenoma
• D Null cell adenoma

Explanation

Non-functioning gonadotroph adenomas are the most common non-functioning pituitary adenomas. They stain positively for FSH, LH, and/or alpha-subunit. Null cell adenomas show no immunohistochemical or hormonal evidence of differentiation. Somatotroph and lactotroph adenomas are functioning tumors with clinical GH or prolactin excess respectively.

Reference: WHO Classification of Tumours: Endocrine and Neuroendocrine Tumours, 5th series, 2022 ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.