A 60-year-old male with no prior history of cancer presented with right greater than left bilateral pleural effusion (A) and multiple lymphadenopathies. The pleural effusion cytology showed very large cells with irregular nuclear contours occasionally with central pseudoinclusions (so-called “doughnut” cells, arrows) and plump amphophilic cytoplasm including many vacuoles (B, Wright-Giemsa stain, ×20; C–F, Wright-Giemsa stain, ×50). On concurrent lymph node biopsy sections, the neoplastic cells are positive for ALK and CD30, while negative for keratin 7, keratin 20, MOC-31, and calretinin, confirming the diagnosis of ALK-positive anaplastic large cell lymphoma (ALCL). Nuclear pseudoinclusion, which is an invagination of nuclear membrane but not a true inclusion, can be a clue for several neoplasms, most notably papillary thyroid carcinoma, and others such as medullary thyroid carcinoma, melanoma, meningioma, lung adenocarcinoma especially those with ALK-rearrangement, and ALCL. Although it is highly uncommon for an ALCL to present as pleural effusion, its diagnosis should be considered if the tumor cells are large with frequent nuclear pseudoinclusions in the pleural fluid.