THU023 Sparse Granulation In Growth Hormone Secreting Adenomas: Clinical Implications Of A Rare Histological Finding

Disclosure: A. Merrill: None. R. Varughese: None. G. Campbell: None. L. Belalcazar: None. Introduction: Acromegaly is an uncommon disease. Endocrinologists may be unfamiliar with the clinical implications of granularity findings on the histology of growth hormone (GH)-secreting adenomas. We present the case of a patient with acromegaly in whom a sparsely granulated (SG) histological subtype was identified post-operatively. We discuss the clinical presentation and therapeutic implications of this finding. Case Presentation: A 36-year-old man was admitted to the hospital with rectal bleeding and incidentally found to have features consistent with acromegaly. Patient reported that over 1 year he had noticed changes in his facial features, enlargement of his hands and had developed hand and knee arthralgias. During the 6 months prior to admission, he experienced worsening fatigue, but denied severe headaches or vision changes. Past medical history was significant for osteosarcoma as a young child treated with an above the knee amputation. Family history was negative for pituitary tumors or colon cancer. Physical exam revealed a blood pressure of 104/53 mmHg and an amputation-adjusted body mass index of 27.4 _kg/ m(2) . He had mild frontal bossing, enlarged nose, macroglossia, swollen hands and foot. Rectal examination revealed hemorrhoids but no masses. Gross visual field deficits were identified at bedside. Laboratory findings were significant for an elevated IGF-1 at 975 ng/mL (83-240 ng/mL) and GH 45.2 ng/mL (0.3-9 ng/mL). Patient was also found to have panhypopituitarism: TSH 1.54 mIU/L (0.45-4.70 mIU/L), Free T4 0.62 ng/dl (0.78 - 2.20 ng/dL); ACTH 13.3 pg/ml (7.2 - 63.3 pg/mL), cortisol AM 3.6 ug/dL (4.5-23.0 ug/dL), peak cortisol after ACTH stimulation 16.0 ug/dL; testosterone 31.6 ng/dl (132-813 ng/dL), LH 1.75 mIU/ml (1.2-8.6 mIU/mL). His hemoglobin A1c was 5.7%. MRI of the brain revealed a large enhancing lobulated sellar/suprasellar lesion of 5.0 x 2.4 x 2.8 cm, with extension to the third ventricle and mass effect on the optic chiasm. Patient underwent partial surgical resection of the large tumor. Pathology identified a SG somatotroph tumor with most cells being negative or weakly positive for GH on immunohistochemical staining. TSH, prolactin, and ACTH stains were negative. There was evidence of residual tumor, which was located superiorly, not accessible through the transsphenoidal route.A colonoscopy and formal visual field testing are pending currently. Patient is waiting for a second surgery via craniotomy and, given the SG finding on histology, pasireotide therapy will be offered. Discussion: The sparsely granulated (SG) subtype is an uncommon variant of GH-producing. Our patient illustrates the aggressive nature of SG GH-producing adenomas. These tumors express more invasive growth and resistance to standard somatostatin analogue therapy. There is a growing recognition that adenoma granulation is an important consideration in the management of acromegaly. Presentation: Thursday, June 15, 2023