“Incidentalomas”. Posterior Pituitary Cyst

Abstract

The term “incidentaloma” is frequently used by radiologists and endocrinologists to describe the accidental discovery of an abnormal image of the sellar region on the brain MRI of an asymptomatic patient. However, a precise analysis of the MRI features permits one in the vast majority of cases to make a precise diagnosis, usually pituitary adenoma, Rathke cleft cyst (RCC), or anatomical variant. The management and follow-up of these “incidentalomas” being quite different, our suggestion is to replace the term “incidentaloma” by “pituitary adenoma—or RCC or anatomical variant—discovered by chance” in medical and radiological reports, keeping the term “incidentaloma” for those cases where the exact diagnosis is impossible. In front of “microincidentalomas” a precise diagnosis can be frequently made, for instance for the frequent T1-hyperintense RCC better demonstrated on axial T1WI than on sagittal T1WI, located strictly on the midline and in intimate contact with the posterior lobe (Figs. 19.1 and 52.1). Pituitary microadenomas are mostly laterally localized, mark an imprint on the sellar floor, and distort the upper surface of the pituitary gland (Fig. 5.1). T1-hypointense and T2-hyperintense images may also correspond to millimetric infarcts or hemorrhagic scars, as found regularly at autopsy of subjects with no pre-existing pituitary symptoms.