Incidental pituitary uptake on FDG PET/CT: Physiologic variants, pitfalls, and pathologic mimics

Abstract

Incidental pituitary uptake on ¹⁸F-deoxy-glucose positron emission tomography combined with computed tomography (¹⁸F-FDG PET/CT) is rare, occurring in <1% of scans, yet its identification carries significant clinical implications. Accurate interpretation requires a systematic diagnostic approach integrating metabolic, structural, and hormonal assessment. While the normal pituitary gland demonstrates low-level or background FDG activity, focal uptake may suggest pathology ranging from physiologic hyperplasia and benign adenomas to inflammatory conditions such as hypophysitis, or malignant etiologies including pituitary neuroendocrine tumors and metastatic disease. The intensity of uptake, quantified by the maximum standardized uptake value (SUV_max), serves as a critical diagnostic indicator; an SUV_max threshold above 4.1 has been proposed to differentiate benign from malignant lesions with high sensitivity and specificity. Complementary pituitary magnetic resonance imaging (MRI) offers essential anatomic correlation to define lesion morphology, extension, and contrast enhancement patterns, while endocrine evaluation helps establish functional activity and hormonal imbalance. Histopathologic confirmation remains reserved for cases with inconclusive imaging or atypical presentation. This review synthesizes available literature, emphasizing PET-based metabolic features and interpretive pitfalls, while acknowledging the role of computed tomography and MRI in comprehensive lesion characterization. Early recognition and appropriate follow-up are crucial to avoid misdiagnosis and to guide timely management of clinically significant pituitary lesions.

Keywords

Pituitary uptake / Incidentaloma / FDG PET/CT / Differential diagnosis

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