Endocrine Abstracts

JOINT2826

Introduction: Positron Emission Tomography (PET-CT) is commonly used for staging primary tumors. Incidental uptake in the pituitary region on PET-CT is a rare finding. The differential diagnosis includes metastasis from the primary tumor, pituitary adenoma, hypophysitis, Langerhans cell histiocytosis, or physiological uptake. While metastasis and pituitary adenomas often differ in clinical presentation and imaging characteristics, both can present with hyperprolactinemia.

Case Report: A 15.5-year-old male patient was referred to the endocrinology service after an incidental finding of increased metabolic activity in the pituitary region on PET-CT. The patient had an initial diagnosis of left proximal humerus osteosarcoma with multiple metastases (pulmonary and bone). He was undergoing chemotherapy as per the GLATO 2006 protocol, which included cisplatin, doxorubicin, and methotrexate. As part of his staging, a FDG-F18 PET-CT scan was performed, which revealed increased metabolic activity (SUV 4.8) at the left proximal humerus, consistent with osteosarcoma (primary tumor). Additionally, the scan showed increased metabolic activity (SUV 7.2) at the sella turcica, suggestive of involvement of the pituitary gland. Hormonal laboratory tests were ordered to assess pituitary function, and a brain MRI with gadolinium contrast was performed, focusing on the pituitary region. The laboratory results revealed hyperprolactinemia with a prolactin level of 686.4 ng/dl, while other pituitary hormones remained within normal limits. Given the potential role of metoclopramide (an antiemetic) as a contributing factor, the medication was discontinued for three weeks. However, hyperprolactinemia persisted, with a subsequent prolactin level of 724 ng/dl. MRI findings showed an enlarged pituitary gland (14 × 17 mm) with focal cystic areas, hypovascularity, and no involvement of the cavernous sinuses. The pituitary stalk was displaced to the left, maintaining its caliber, and the neurohypophysis was intact. The optic chiasm was preserved. These findings were consistent with a pituitary adenoma with cystic changes (Knosp classification 0). Notably, the patient had no clinical signs of hyperprolactinemia, and neuro-ophthalmological examination was normal. Based on these imaging and biochemical findings, the diagnosis of a macroprolactinoma was assumed. Treatment with cabergoline (0.5 mg weekly) was initiated, with good tolerance. A new laboratory test and follow-up MRI under treatment are pending.

Conclusion: To date, there is no established association between osteosarcoma and prolactinoma in the literature. Although PET-CT SUV values can assist in differentiating between physiological and pathological pituitary uptake, it is crucial to complete evaluation with hormonal testing, pituitary-focused MRI, and ophthalmological assessment for proper diagnosis, follow-up, and treatment.