Cytologic manifestations of Hodgkin lymphoma in serous effusions

Serous effusions occur in a small group of patients with classic Hodgkin lymphoma (cHL). Most effusions are benign inflammatory fluids. Malignant effusions predominantly in patients with treated relapsed diseases or rarely as a primary manifestation are diagnostically challenging to cytopathologists. Established cases of cHL with effusions were retrieved. Cytology slides were screened looking for Reed-Sternberg-Hodgkin (RSH) cells and patterns of background inflammatory cells. Cellblocks and their corresponding immunocytochemistry (ICC) slides were examined. The cytologic findings were correlated with nodal biopsy histopathologic and immunohistochemical features. We found six cases of benign and malignant pleural and pericardial effusions in patients with mediastinal nodular sclerosis-type cHL. Various cytomorphologic patterns were observed. Slides revealed sparsely scattered either isolated or aggregated mononuclear, binucleated and multinucleated RSH-like cells. Some may have been either disregarded as reactive mesothelial or histiocytic cells, or confused with other RSH-like malignant cells. The background varied between characteristic mixed inflammatory milieu, predominantly small lymphocytic or lymphohistiocytic with or without reactive mesothelial cells. Cytologic examination showed three positive cases (two cases with RSH cells confirmed by cellblock section ICC, one case with a mixed inflammatory infiltrate), and three benign effusions (one case with atypical RSH-like reactive mesothelial cells confirmed by ICC). Effusions associated with cHL exhibit different cytologic patterns. A high level of vigilance with utility of ICC has an important role in suspecting primary cases and confirming recurrences in known cases. The various cytologic patterns of cHL-associated benign and malignant effusions might reflect parallel pathophysiologic mechanisms.