Histopathological diagnoses of squamous intraepithelial neoplasia, carcinoma in situ and early invasive cancer of the oesophagus: the Japanese viewpoint

Recent advances in endoscopic techniques have improved the diagnostic and therapeutic options for early oesophageal cancers. As a result, approximately 15% of patients with oesophageal cancer have recently undergone endoscopic resection in Japan. Although it is rather easy to histopathologically diagnose apparent invasive squamous cell carcinoma, diagnoses of intraepithelial neoplasia, squamous cell carcinoma in situ, and early invasive cancer are often difficult because of mild architectural and cytological abnormalities. An oblique line or front formation is an important histological finding for the diagnosis of neoplastic lesions. Loss of polarity with increased cellular density and nuclear atypia such as enlargement, irregularity in nuclear size and shape, hyperchromasia, overlapping, dyskeratosis, and conspicuous eosinophilic nucleoli are also listed as diagnostic indicators. Oesophageal cancer increases the risk of lymph node metastases even in pT1a-MM cancers (tumour invasion into the muscularis mucosa). pT1a-LPM cancers (tumour invasion into the lamina propria mucosae) with sprouting or droplet infiltration are also capable of lymph node metastasis. Although invasion is the most important criterion for distinguishing intraepithelial neoplasia from squamous cell carcinoma in Western countries, estimating invasion is quite difficult, especially invasion of the lamina propria as that would constitute a downward invasion. In addition, squamous cell carcinoma in situ resembles low-grade intraepithelial neoplasia, causing difficulty in diagnosing squamous lesions. Over-and under-diagnosis should be avoided for providing appropriate clinical management. Advances in endoscopic techniques warrant improvement of the histopathological diagnostic criteria for oesophageal cancers.