Figure 1.

(A,B) ALCL is a neoplasm composed of sheets of large pleomorphic/anaplastic tumor cells with abundant cytoplasm. Occasional multinucleated cells and Reed-Sternberg-like cells are seen. (B) “Hallmark” cells are characteristic of this neoplasm (arrow). (C,D) Most cases of ALK- ALCL with the DUSP22 rearrangement have a more monotonous appearance and are less pleomorphic. This case has a particular starry-sky appearance. (D) Cells with central nuclear pseudoinclusions or a “doughnut” nuclear shape are commonly seen (arrow).