Morphology and immunophenotype of anaplastic large cell lymphoma, common type.

(A) Cytologic features of ALCL, common type, in a paraffin section (hematoxylin and eosin). (B) Cytologic features of ALCL, common type, in a touch imprint (May-Grünwald-Giemsa). (C) Dissemination of ALCL cells in a marginal sinus. MS indicates marginal sinus; GC, reactive germinal center (hematoxylin and eosin). (D) CD30 immunoreactivity of ALCL, common type. All tumor cells are CD30⁺. Note the sinusoidal dissemination (arrow) and the perifollicular homing of the CD30⁺ tumor cells (antibody clone Ber-H2; alkaline phosphatase–antialkaline phosphatase [APAAP]). (E) Immunoreactivity of an ALCL of common type for the cytotoxic molecule perforin. The sinusoidal dissemination of the tumor cells (arrow) and a small reactive cytotoxic cell (arrowhead) are indicated (antibody clone P1-8; APAAP). (F) Immunoreactivity of an ALCL of common type for the anaplastic lymphoma kinase (ALK). There is strong labeling in the cytoplasm as well as in the nucleus (antibody clone ALKc; APAAP). (G) An ALCL of common type with labeling for ALK restricted to the cytoplasm (antibody clone ALKc; APAAP).