Immunohistochemistry combined with Alcian Blue-Periodic Acid Schiff (AB-PAS) staining in the differentiation of ovarian seromucinous borderline tumors and mucinous borderline tumors

This study aimed to evaluate the clinicopathological features of ovarian seromucinous borderline tumors (SMBTs) and mucinous borderline tumors (MBTs) and to establish a diagnostic approach using immunohistochemistry (IHC) and Alcian Blue-Periodic Acid Schiff (AB-PAS) histochemical staining. A retrospective analysis of 73 MBT and 34 SMBT cases was conducted at a single institution. Clinical, pathological, IHC (CK7, CK20, ER, PAX8), and histochemical (AB-PAS) features were compared. Both of SMBTs and MBTs frequently occurred in patients under 40 years. Patients with SMBTs were older, their tumors were of significantly smaller tumor size, and were more likely to be bilateral and associated with endometriosis than MBTs. Recurrence rates were 9.1 % (SMBTs) and 1.9 % (MBTs). 85.3 % of SMBTs exhibited CK7 cytoplasmic positive (+++) as compared with 46.6 % of MBTs. All SMBTs were CK20-negative and 68.5 % of MBTs showed CK20 cytoplasmic positivity. 100 % of SMBTs showed ER nuclear positivity, whereas all MBTs were ER-negative. PAX8 were consistently expressed (++/+++) in 97.1 % of SMBTs but 11 % in MBTs, respectively. AB-PAS staining distinguished SMBTs (acidic mucin: blue) from MBTs (neutral mucin: magenta; goblet cells: blue). Overall, our study affirms that SMBTs and MBTs exhibit distinct clinicopathological profiles. A combined IHC panel (CK7, CK20, ER, PAX8) with AB-PAS staining enhances diagnostic accuracy, potentially guiding clinical management.