ALK and esophageal squamous cell carcinoma: Since discovery of the fusion NPM-ALK protein, more than 20 ALK fusion partners have been observed not only in ALCL but also in diseases such as inflammatory myofibroblastic tumor (IMT), non-small cell lung cancer (NSCLC), renal carcinoma, breast cancer, colon carcinoma, serous ovarian carcinoma, oesophageal squamous cell carcinoma (ESCC) and diffuse large B cell lymphoma (DLBLC) [4].