High numbers of tumor-associated macrophages correlate with poor prognosis in patients with mature T- and natural killer cell lymphomas.

Various studies on lymphoma microenvironment have demonstrated the prognostic impact of tumor-associated macrophages (TAMs) in patients with B-cell lymphoma. Little is known about the correlation between TAMs and treatment outcome in mature T- and natural killer (NK) cell lymphomas. We analyzed the prognostic relevance of CD68+ TAMs by immunohistochemical analysis in 64 Chinese patients with mature T- and NK-cell lymphomas. Higher number of infiltrated TAMs was significantly related to B symptoms and extranodal involvement (p < 0.05). The TAMs content did not differ significantly between pathological subtypes. Using the mean value of TAMs per high-power field (hpf) as the cutoff point (87/hpf), 36 cases (56.2 %) were categorized as low level of TAMs content and 28 cases (43.8%) as high level. Patients with high level of TAMs content had a worse 5-year overall survival compared to those with low level (28.1 vs. 44.3 %, p = 0.039). In multivariate analysis, TAMs content remained an independent biological variable for survival distinct from the International Prognostic Index (Cox multivariate model, p = 0.009). High TAMs content indicated an adverse overall outcome in mature T- and NK-cell lymphomas. Our results show that expression of stromal TAMs may become a useful marker for prognosis of mature T- and NK-cell lymphomas.