Lacunar cells are the predominant variant of Reed-Sternberg (RS) cells in nodular sclerosis subtype of classic Hodgkin lymphoma. Classic binucleated RS cells are rare or absent. In formalin-fixed tissues, these cells appear retracted or shrunken and contained in a lacuna. The cytoplasm is condensed in the perinuclear region, leaving an empty space (lacuna) around it. The lacunar spaces are an artifact of formalin fixation and are not seen in B5-fixed tissues. The nucleus is multilobated with complex infoldings and coarse chromatin. The nucleoli are smaller than those seen in classic RS cells. Lacunar cells may be scattered singly throughout the lymph node or arranged in compact clusters or diffuse sheets (especially in grade II nodular sclerosis).