The study by Dr Yasunaga et al [1] delineating immunohistochemical features of müllerian mucinous borderline tumors (MMBTs) compared with other types of low-grade ovarian tumors was of great interest.After describing the features of MMBT and mixed-epithelial borderline tumors in 1988 [2,3], I studied the immunohistochemical features of these 2 tumors compared with intestinal-type mucinous borderline tumors (IMBTs) [4]. We found a distinctively different staining pattern in the borderline tumors of...