PMC9846627_01
First MRI-scan. Sagittal T2-weighted (A) and post-contrast T1-weighted (B) images. Sellar and suprasellar mass involving posterior lobe and infundibulum of the pituitary gland, with low signal on T2-images. Compression of mammillary body, optic chiasm and tracts, third ventricle (infundibular recess).
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He underwent a brain MRI which showed a voluminous pituitary mass (18.5x19.5x15.5 mm diameter;  Figure 1 ) involving the posterior lobe and the pituitary stalk with suprasellar invasion, causing posterior sellar enlargement, and compression of the surrounding structures including the optic chiasm and the optic tracts, with loss of neurohypophysis signal.
Histopathological examination of the sellar mass, consistent with a pituitary localization of an Adenocarcinoma, showing a pseudopapillary and glandular architectural pattern with necrosis and brisk mitotic activity (EE 20x). Insert: Immunostaining for CDX2 (20x).
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Subsequent histologic examination showed a poorly differentiated HER-2-positive adenocarcinoma of uncertain origin ( Figure 2 ).
One-month follow-up MRI scan. Sagittal T2-weighted (A) and post-contrast T1-weighted (B) images. Post-surgical sellar modification with increase of the residual tumor in suprasellar spaces, third ventricle invasion and mammillary body compression and infiltration.
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A new brain MRI showed an extension of the post-surgical residual tumor, with compression of optic chiasma, hypothalamus, mammillary bodies, and third ventricle ( Figure 3 ).
Follow-up MRI scan at 139 days. Sagittal T2-Weighted (A) and post-contrast T1-weighted (B) images. Post-surgical sellar modification with small residual tumor in suprasellar/infundibular region. Axial post-contrast T1-weighted images (C-F): multifocal leptomeningeal dissemination (arrows).
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A follow-up MRI study was performed after 139 days that showed multifocal leptomeningeal dissemination in the posterior cranial fossa ( Figure 4 ).