Examples of anti-ALK immunostaining. (A) Large anaplastic cells from case no. 1 with the inv(2)(p23q35) showing strong diffuse ALK positivity confined to the cytoplasm. (B) In comparison, a case of CD30⁺ ALCL with the t(2;5)(p23;q35) showing expression of the NPM-ALK protein both in the cytoplasm and the nucleus is shown (A and B: lymph node formalin-fixed paraffin sections immunostained with the ALKc monoclonal antibody; APAAP technique; original magnification ×800).