Koshi Ikeda MD, Presenter: Nothing to Disclose

Naoto Ohmura MD, Abstract Co-Author: Nothing to Disclose

Minoru Maehara, Abstract Co-Author: Nothing to Disclose

Tatsuya Sugimoto MD, Abstract Co-Author: Nothing to Disclose

Atsushi Komemushi MD, Abstract Co-Author: Nothing to Disclose

Satoshi Sawada MD, Abstract Co-Author: Nothing to Disclose

Although previous investigators have reported that parotid pleomorphic adenomas exhibit high signals on T2-weighted images, a small number of cases may exhibit iso signal and low signal. We performed contrast examination of signal intensity on T2-weighted images and pathological findings in parotid pleomorphic adenomas.

Between 1996 and 2002, we examined 42 parotid pleomorphic adenomas. These were classified into three types on the basis of the signal intensity of the tumors on T2-weighted images; Type 1 presents markedly high signal compared with normal parotid tissues, Type 2 presents a slightly elevated signal, and Type 3 presents a lower signal. For each type, the pathologic findings were compared with the signal intensity of the tumor on T2-weighted images.

An ellipse or lobulation of the tumor contour was seen on T2-weighted images. The boundary with the normal parotid tissues was clear. The low signal capsule on T2-weighted images markedly defined the surrounding tumor. The pathologic findings of the three types were classified according to signal intensity. Type 1 consisted primarily of myxoid and chondroid stroma (31 cases, 74%). Type 2 consisted primarily of epithelial cells (eight cases, 19%). Type 3 consisted primarily of myxoid and chondroid stroma with marked fibrosis (3 cases, 7%).

Pleomorphic adenoma generally consist of the duct-lining epithelial cells and myxoid, chondroid stroma. The myxoid and chondroid stroma, containing mucin, exhibited a high intensity signal. Epithelial cells predominantly exhibit iso-signal. Myxoid and chondroid stroma with marked fibrosis exhibit a low intensity signal. Epithelial cells are dense, and malignant parotid tumors with little stroma, such as adenocarcinomas, have been reported to exhibit a low intensity signal on T2 weighted images. Lobulation of the tumor contour and low signal capsule on T2-weighted images of malignant parotid tumors can be important for differential diagnosis, as pleomorphic adenomas may exhibit a low intensity signal.

Ikeda, K, Ohmura, N, Maehara, M, Sugimoto, T, Komemushi, A, Sawada, S, Contrast of Signal Intensity on T2-weighted Images and Pathological Findings in Parotid Pleomorphic Adenoma.  Radiological Society of North America 2004 Scientific Assembly and Annual Meeting, November 28 - December 3, 2004 ,Chicago IL. http://archive.rsna.org/2004/4410882.html