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Pituitary mass with a fluid-fluid level

Case contributed by Chris O'Donnell
Diagnosis certain

Presentation

Elevated prolactin. Headache with no visual disturbance, ? pituitary adenoma.

Patient Data

Age: 40 years
Gender: Male

Cystic mass located in the midline of the pituitary fossa causes mild expansion. There is a fluid/fluid level on the axial scan (arrow) and surrounding enhancement.

Conclusion:

The presence in a fluid-fluid level suggests that this lesion is more likely a cyst/necrotic adenoma. The alternative diagnosis, considered less likely, is that of a Rathke's cleft cyst.

Case Discussion

Although distinguishing between a cystic/necrotic pituitary adenoma and a Rathke's cleft cyst can be challenging the presence of a fluid-fluid level is quite specific for the diagnosis of an adenoma (specificity, 96.4%). This is in contrast to an intracystic dot which favors a Rathke's cleft cyst.

Importantly, elevated prolactin is not necessarily due to secretion of prolactin, rather a mass that compresses the pituitary stalk can lead to interruption of dopamine flow from the hypothalamus through the hypophyseal-portal circulation to the anterior pituitary. Unlike other hypothalamic control of the pituitary, control of prolactin secretion is primarily inhibitory. See causes of elevated prolactin.

Unfortunately, in this instance, no followup is available.

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