口腔癌頸部リンパ節転移の画像所見と病理所見の対応について Imaging in the diagnosis of cervical lymph node metastases in patients with oral cancer : correlation between imaging findings and histopathologic results

The presence of regional lymph node metastases has a major influence on the prognosis of patients with oral cancer. Modern imaging techniques play a major role in the diagnosis of lymph node metastases. The characteristics of metastatic lymph nodes that can be depicted are increased size, a rounder shape, and heterogeneity caused by central necrosis, cystic degeneration, or tumor keratinization. Abnormal internal structure of the lymph node is a reliable criterion for diagnosing metastases rather than size or shape. Central necrosis and/or cystic degeneration are corresponding to the focal area of low attenuation with or without rim enhancement on post-contrast CT, whereas the predominantly hypoechoic with heterogeneous internal echogenicity on ultrasonography. On the contrary, tumor keratinization is corresponding to a focal area of high attenuation on non-contrast CT, whereas a focal hyperechoic area not in continuity with the surrounding fatty tissue on ultrasonography. Although central necrosis or tumor keratinization is a very reliable criterion for lymph node metastases, it is unfortunately not visible in every metastatic lymph node. The minimal axial diameter is a better criterion than the maximal axial diameter and a round shape is considered more suspicious than an oval or flat shape. Additionally, watchful observation of individual lymph nodes is essential. We recommended the use of follow-up examination of ultrasonography at an interval of 1 month for at least one year and a half after treatment of the primary tumor. In this article, the comparison between imaging and histopathological findings on a side-by-side basis was described.