CD5‐positive follicular lymphoma characterized by CD25, MUM1, low frequency of t(14;18) and poor prognosis

CD 5‐positive follicular lymphoma ( FL ), although rare, has been described in a number of case reports. However, a statistically valid, clinicopathological comparison between CD 5‐positive FL and CD 5‐negative FL has never been performed because of its rarity. We statistically compared clinicopathological characteristics of 22 cases of CD 5‐positive FL , diagnosed by immunohistochemistry, flow cytometry and morphological findings, with those of 62 cases of FL without CD 5 expression (control cases). CD 5‐positive FL patients showed a higher tendency of peripheral blood involvement ( P = 0.076) and a higher frequency of CD 25 expression ( P = 0.0004) and MUM 1 protein expression ( P = 0.0008), and a lower frequency of t(14;18)(q32;q21) ( P = 0.017). The overall survival ( OS ) curve of CD 5‐positive FL was significantly worse than that of control cases ( P = 0.0266), although progression‐free survival curves did not show a significant difference ( P = 0.7899). Moreover, CD 5 expression was shown to be an independent poor prognostic factor for OS in both univariate analysis [ H azard R atio ( HR ), 3.63; P = 0.0464] and multivariate analysis ( HR , 57.16; P = 0.0001). CD 5‐positive FL showed different clinicopathological characteristics from FL lacking CD 5 expression. These results suggest that CD 5‐positive FL should be considered a different type of FL , and its clinicopathological management should be conducted differently.