A 55-year-old man is diagnosed with a pituitary adenoma secreting GH. The somatotroph adenoma is most reliably distinguished from a normal pituitary on histology by:

• A Presence of Rathke cleft cysts adjacent to the tumor
• B Loss of normal pituitary reticulin network replaced by sheets of monomorphic cells without acinar architecture ✓
• C Mitotic activity and necrosis indicating malignant transformation
• D Psammoma bodies distributed throughout the tumor stroma

Explanation

Normal anterior pituitary has an acinar (alveolar) architecture supported by a reticulin framework. The key histological hallmark distinguishing pituitary adenoma from normal pituitary or hyperplasia is loss of this reticulin network, replaced by sheets or trabeculae of monomorphic cells. Reticulin stains (Gordon-Sweet) clearly demonstrate this architectural disruption. Malignant pituitary carcinoma requires CSF or systemic metastasis as the criterion; mitoses alone are insufficient. Psammoma bodies are characteristic of papillary thyroid carcinoma and meningiomas.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.