Aims: Recent studies have provided the concept of invasive intramucosal colorectal carcinoma (CRC), and a case of intramucosal CRC with lymphatic invasion has been reported; however, the characteristics of such cases and the risk of lymph node metastasis have never been investigated. Therefore, we aimed to assess the pathological characteristics of intramucosal CRCs with lymphovascular invasion as well as the possibility of lymph node metastasis as an indication for additional surgery.
Methods and results: To delineate the histological features of intramucosal CRCs with lymphovascular invasion, we analysed several histological features and compared their incidence among nine such cases, as well as 20 other cases of intramucosal CRCs without lymphovascular invasion. High-grade tumour budding and a pattern of 'eosinophilic cytoplasm and round nuclei with inflammatory reaction (ERI)' were morphological characteristics of intramucosal CRCs with lymphovascular invasion, compared with those without lymphovascular invasion (both P < 0.05). Among the seven lymph node-dissected cases of intramucosal CRCs with lymphovascular invasion, none showed lymph node metastasis.
Conclusions: In intramucosal CRCs with lymphovascular invasion, high-grade tumour budding and the 'ERI' pattern are morphological characteristics that are distinct from those of non-invasive CRC, which is synonymous with high-grade dysplasia. Further studies using a larger number of cases by focusing on the above-mentioned histological pattern are expected to clarify the potential of lymph node metastasis of such cases.
Keywords: intramucosal colorectal carcinoma; lymphovascular invasion; metastasis; tumour budding; ‘eosinophilic cytoplasm and round nuclei with inflammatory reaction’ pattern.
© 2019 John Wiley & Sons Ltd.