Endocrine Abstracts

JOINT3439

Pituicytoma is a rare, low-grade spindle-cell astrocytic tumor of the posterior pituitary or its stalk, classified as a WHO grade I central nervous system tumor. It’s typically located in the sellar or suprasellar region and is often misdiagnosed as other sellar lesions such as pituitary adenoma or craniopharyngioma. Clinically, a pituicytoma presents with signs of mass effect and hypopituitarism due to compression of the pituitary gland. It’s also common to have hyperprolactinemia because of stalk effect. Additionally, diabetes insipidus was described. While less than 200 cases of pituicytoma have been reported in the literature, endocrine hyperfunction, particularly Cushing’s disease and acromegaly, is a rare occurrence. Here, we report two cases of pituicytoma associated with Cushing’s syndrome. Case 1 A 38-year-old woman presented with hirsutism mostly on the face and the abdomen. Eleven years earlier, she had undergone endocrinological evaluation for hirsutism, acne, and a 10-kg weight gain. In 2023 tests showed hypercortisolism: urinary free cortisol (UFC) 1.12 ULN, ACTH 56 pg/ml, cortisol after 1 mg dexamethasone suppression test (F-1mgDST) 6.58 µg/dl. 8-mg overnight dexamethasone suppression test and desmopressin stimulation test were suggestive for Cushing’s disease. MRI identified a 3-mm hypointense lesion on T1-weighted sequences in the right anterolateral pituitary, suggestive for pituitary microadenoma. She underwent surgery, achieved disease remission and developed secondary adrenal insufficiency. Histology revealed that the lesion was a pituicytoma. Case 2 A 40-year-old woman complained of with symptoms including hirsutism, buffalo hump, easy bruising, hypertension, and weight gain over the past two years. Laboratory tests confirmed a diagnosis of overt Cushing’s disease (UFC 5.47 ULN, ACTH 53 pg/ml, F-1mgDST 17.4 µg/dl,) and MRI showed a 4-mm microadenoma in the left pituitary. The desmopressin test result was consistent with Cushing’s disease (ACTH increase of 115% over baseline). She underwent transsphenoidal surgery, achieved clinical remission and developed adrenal insufficiency. Histological features were indicative of pituicytoma.

Discussion: About 15 cases of pituitary tumors associated with Cushing’s syndrome have been documented so far. Since pituicytomas are classified as gliomas, hormone secretion is considered unusual. The observed ACTH production could potentially result from an undetected microadenoma, such as a Crooke’s cell adenoma, or from paracrine signaling that stimulates the proliferation of anterior pituitary cells. This coexistence might not be coincidental but could suggest an unknown pathophysiological connection or a shared progenitor cell origin. Performing histological analysis with ACTH immunostaining could help to identify hidden lesions and provide insight into the underlying mechanisms.