Unusual Magnetic Resonance Image of an Insulinoma with Extensive Desmoplastic Reaction

Nagihan Inan, Arzu Arslan, Gur


Context Unlike other islet-cell tumors, insulinomas are usually benign. Most insulinomas have a high signal intensity onT2-weighted images and a low signal intensity on T1-weighted images, and are hyperintense on immediate post-gadolinium images. However, in rare cases, insulinomas may be hypointense on T2-weighted images and on immediate post-gadolinium images, mimicking a ductal adenocarcinoma. Case report We present a case of a surgically proven insulinoma which was hypointense on both T2-weighted and immediate postgadolinium T1-weighted images, buthyperintense on late phase T1-weighted images. Histopathological examination of the surgical specimen revealed a prominent desmoplastic reaction which accounted for the low signal on T2-weighted images and the contrast enhancement pattern. Delayed contrast enhancement reflects the desmoplastic component of this tumor. Conclusions Insulinomas with an extensive desmoplastic reaction may appear hypointense on T2-weighted images with minimal enhancement on immediate post-gadolinium images. Late phase fat-suppressed T1- weighted post-gadolinium images may be useful in the detection of such tumors.

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