Endocrine Abstracts

Positron emission combined with computed tomography using ¹⁸F-deoxy-glucose (FDG–PET/CT) is increasingly used in the staging and detection of malignant disease. Normal pituitary is not visualized by routine FDG–PET/CT and its radiological evaluation relies predominantly on magnetic resonance imaging (MRI). The role of FDG–PET/CT in differential diagnosis of sellar mass, in patients investigated for malignant disease, will be discussed.

Case 1

FDG–PET/CT restaging was requested for 70-year-old male suspected of having hilar lymphadenopathy. In the past he was treated for two malignancies (lung and rectal carcinoma) but FDG uptake was remarkable only in the sellar region. Although MRI confirmed a pituitary mesoadenoma, clinically he was asymptomatic with normal anterior pituitary function and no diabetes insipidus. Immunostaining after trans-sphenoidal pituitary surgery confirmed diagnosis of silent gonadotroph–pituitary adenoma.

Case 2: In a 43-year-old male patient with sudden onset of headache, nausea, fatigue, dizziness and visual loss pituitary MRI disclosed an intra and suprasellar lesion with a narrow waist while on scull X-ray sella appeared normal. Panhypopituitarism without diabetes insipidus, was diagnosed and replaced. Chest X-ray rose the suspicion of a tumor in the right lung, subsequently confirmed by CT. On FDG–PET/CT an avid uptake was detected in the lung and pituitary. After an open biopsy of the lung tumor a microcellular bronchial carcinoma was diagnosed and patient underwent chemotherapy.

In asymptomatic patients undergoing staging for malignant disease, an avid FDG uptake in the sellar region can disclose a pituitary incidentaloma, which can be confirmed by pituitary MRI. In patients with sudden onset of sellar mass symptoms and hypopituitarism (and/or diabetes insipidus), specific pituitary MRI findings may raise the suspicion of metastasis in the pituitary. Therefore, when clinical suspicion of malignancy is present spying on cancer with FDG–PET/CT may have a role in pituitary imaging, detection of primary tumor and distant metastases.