Hodgkin's lymphoma (HL) is a B cell neoplasm and is classified into two categories: nodular lymphocyte predominant Hodgkin's lymphoma (NLPHL) and classical Hodgkin's lymphoma (CHL). CHL is a clonal lymphoid neoplasm originating from germinal centre B cells; the diagnosis is based on typical Hodgkin and Reed-Sternberg (HRS) giant cells in an inflammatory background. Histologically, four histological subtypes of CHL have been identified: nodular sclerosis, lymphocyte rich, mixed cellularity and lymphocyte-depleted.1 Immunohistochemically, HRS cells in nearly all cases are positive for CD30 and for CD15 in the majority (75–85%) of cases according to the 2008 WHO classification.1 ,2 The histological diagnosis of CHL in most instances is straightforward, particularly with the aid of immunohistochemistry. Other than the prerequisite of CD30 expression by HRS cells, CD15 is frequently referred to as a ‘positive’ marker for diagnosis. Apart from diagnostic importance, CD15 expression is of prognostic value. Lack of CD15 expression in CHD has been reported to be a poor prognostic factor in patients with CHL.3 ,4

In the author's experience in Taiwan, the frequency of CD15 expression in CHL is low, which prompted the author to systemically investigate the prevalence of …