12526 Acromegaly Secondary to Sparsely Granulated Adenoma

Abstract Disclosure: D. John: None. M. Kinaan: None. J. Titus: None. K. Lamar: None. The most common pathological finding in acromegaly is a densely granulated adenoma which is composed of large round eosinophilic cells with prominent nucleoli and spherical nuclei that closely resemble a somatotroph cell. Less common finding is a sparsely granulated adenoma that is composed of sheets of poorly cohesive, pleiomorphic nuclei, chromophobic cells. We present a case of a 58-year-old gentleman presenting to our endocrine clinic for evaluation of a pituitary macroadenoma. The patient was hospitalized for nausea, vertigo, headaches, and blurring of vision. CT brain at that time showed a pituitary mass measuring 2.4 x 1.6 x 1.7 cm centered in the right cavernous sinus and inseparable from the pituitary gland. Hormonal work-up in the hospital was remarkable for high GH level. IGF-1 level was not done. Patient was advised to follow-up with neurosurgery as outpatient and no emergent surgery was planned. In the clinic, patient denied symptoms of DI, adrenal insufficiency or hypothyroidism. He has history of hypogonadotropic hypogonadism and was on testosterone therapy, but he stopped it since his hospitalization. On physical examination, he was noted to have macroglossia, deep voice, prominent jawbone, and soft tissue swelling in the hands and feet. Patient did not have any visible joint swelling. He stated he did not notice these changes personally and that he’s always been a “big guy” and always had a deep voice since he was a teenager. Repeat hormonal workup (done at 8 AM) showed: normal CMP, ACTH, cortisol, prolactin, TSH, T4, and T3. Testosterone was low with LH and FSH inappropriately within the normal reference range consistent withhypogonadotropic hypogonadism. IGF-I was elevated at 628ng/mL with a Z score of 3.9. These findings were consistent with acromegaly. He underwent surgery for tumor resection and pathology report showed that about 40% of the cells demonstrated weak immunoreactivity for GH, and rare (less than 1%) prolactin-positive cells were present within the tumor. The specimen was negative for TSH, ACTH, FH, and LH immunostains. Immunostain for CAM5.2 showed predominantly perinuclear dot-like immunoreactivity. The *MIB1 proliferation index is about 1%. The findings were consistent with a sparsely granulated gonadotrophic adenoma, which may demonstrate aggressive behavior. Postoperative MRI showed postoperative changes with residual pituitary tissue (normal gland vs. residual tumor). Postoperative cortisol >16. Postoperative GH dropped from 4.39 to 2.69 after 1 month. After 3 months, patient was doing well with no symptoms. However, IGF1 level (>400) showing that surgery was not curative. Currently he is awaiting gamma knife radiation therapy with possible medical therapy afterwards. Our case will provide an overview of the specific management considerations for these tumor and how they differ from densely-granulated tumors. Presentation: 6/3/2024