[Expression of sialylated CD15 in classical Hodgkin lymphoma following sialidase digestion]

Objective: To detect the expression of sialylated CD15 (CD15s) in the tumor cells of classical Hodgkin lymphoma using a modified immunohistochemical approach. Methods: From 2009 to 2024, 53 cases of classical Hodgkin lymphoma were collected in the Department of Pathology, Peking University Cancer Hospital, in which 21 cases that were CD15-negative or showed only focal weak positivity were selected. Immunohistochemical staining for CD15 was performed on a Leica automated stainer using three different antibody clones (MMA, Carb3, and IHC527). Tissue sections were digested with sialidase at varying concentrations and incubation times, followed by immunohistochemical staining with the MMA clone. Multiplex immunofluorescence was applied for co-staining of CD15 (MMA) and CD30 (JCM182), and analysis was conducted using APTIME and HALO software. Results: There were 30 male patients and 23 female patients, with an age range of 14 to 73 years and a median age of 32(26,46) years. None of the three CD15 antibody clones significantly improved the CD15 positive rate in the 14 completely negative and 7 weakly positive cases, with no notable differences observed among the clones(P>0.05). After sialidase digestion, tissue morphology remained well-preserved. Optimal CD15 staining was achieved with a 1∶1 diluted sialidase incubated at 37 ℃ for one hour. This treatment significantly enhanced the detection rate of CD15 antigen in Hodgkin Reed-Sternberg cells (P<0.001). Conclusion: Sialidase digestion effectively unveils sialylated CD15 expression in classical Hodgkin lymphoma, markedly improving its detection in HRS cells.