ESR1 and colorectal adenocarcinoma: Although the immunohistochemical staining is somehow more specific, it tends to be immunopositive for the CK-7, and immunonegative for the CK-20, in contrast to the colorectal adenocarcinoma which tend to be immunopositive for CK-20 (65.9 %), and immunonegative for CK-7 (82.9 %) [17], ER and PR are usually positive, but their absence doesn’t exclude the diagnosis of RMCs.