SUN-007 - When Silent Is Not Silent: A Functioning Sparsely Granulated Corticotroph Tumor

Background: Sparsely granulated corticotroph tumors (SGCTs) represent a minority of corticotroph adenomas, accounting for approximately 15–20% of cases. Unlike densely granulated corticotroph tumors, SGCTs are more commonly clinically silent, staining positive for ACTH without causing overt hypercortisolism. Functioning SGCTs resulting in Cushing’s disease are very rare and may present diagnostic and management challenges. We present a case of a functioning sparsely granulated corticotroph macroadenoma associated with overt ACTH-dependent hypercortisolism.

Clinical

Case: A 73-year-old woman with history of hypertension, hyperlipidemia, and type 2 diabetes presented with progressive neurologic symptoms, including drooping of her right eyelid and facial asymmetry for three weeks. She reported no headaches, visual changes, galactorrhea, fatigue, weight changes, heat or cold intolerance.

Physical examination was notable for obesity, right eye ptosis, and blunting of her right nasolabial fold. Brain MRI demonstrated a 1.8 × 1.6 × 1.4 cm pituitary mass within the pituitary fossa extending into the suprasellar cistern and right cavernous sinus, with superior abutment of the optic chiasm, consistent with a pituitary macroadenoma with local mass effect. Biochemical evaluation revealed ACTH-dependent hypercortisolism, with positive low dose dexamethasone suppression testing and an ACTH level of 207 pg/mL (reference < 46 pg/mL), consistent with Cushing’s disease. Given the tumor size and associated neurologic findings, neurosurgical evaluation was pursued. The patient underwent endonasal transsphenoidal resection of the pituitary mass. Postoperatively, she developed secondary adrenal insufficiency with hypotension and low cortisol levels requiring glucocorticoid replacement.

Histopathologic examination confirmed a sparsely granulated corticotroph pituitary neuroendocrine tumor, with positive ACTH immunostaining and characteristic cytologic features. Additional laboratory findings included hypercalcemia with elevated parathyroid hormone levels, consistent with primary hyperparathyroidism, and the patient is currently undergoing genetic evaluation for multiple endocrine neoplasia.

Conclusion: This case highlights a rare presentation of a functioning sparsely granulated corticotroph tumor causing Cushing’s disease. Although SGCTs are more frequently silent, they may occasionally present with overt hormone excess and significant mass effect. Recognition of this uncommon phenotype is important for accurate diagnosis, prognostication, postoperative management, and long-term follow-up, as SGCTs have been associated with more aggressive behavior and higher recurrence rates compared with densely granulated corticotroph tumors.

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