STAT6 Can Be Used in the Diagnosis of Hodgkin Lymphoma: There Are Differences in Expression Among Subtypes.

New markers are needed to aid in the diagnosis, typing, and determination of targeted treatment options in Hodgkin lymphoma. STAT6 is one of the most frequently reported mutations in classic Hodgkin tumors and can also be detected immunohistochemically. Our study aimed to investigate the role of the STAT6 (EP325) immunostain, diagnosing Hodgkin lymphoma, its staining frequency, immunolocalization, and its relationship with EBV. Sixty-eight patients representing each Hodgkin lymphoma subtype were included in the study. Two patients had nodular lymphocyte-predominant type Hodgkin, 32 had nodular sclerosis, 14 had mixed type, 10 had lymphocyte-depleted, and 10 had lymphocyte-rich type Hodgkin subtypes. STAT6 (EP325), CD30 (Ber-H2), EBV (CS.1-4) immunohistochemistry, EBER CISH and H&E slides applied to the tumors were examined. STAT6 was positive in 90% (61/68) of all lymphomas. Immunoreactivity with STAT6 was present in all tumors of the nodular sclerosis and lymphocyte-depleted subtypes. A total of 10/14 (71%) of mixed cell subtype tumors and 9/10 (90%) lymphocyte-rich subtype tumors were STAT6 positive. STAT6 staining was not detected in 2 (100%) nodular lymphocyte-predominant subtype. A total of 31% (19/61) of STAT6-positive tumors were also positive for EBV. While STAT6 positivity may be diagnostic of classic Hodgkin's subtypes, STAT6 negativity may be useful for diagnosis of nodular lymphocyte predominant type.