Cell Cannibalism: A cytological study in effusion samples

Background: Cytological examination of effusion fluid is a relatively easy and quick method for the diagnosis of primary or secondary malignancy. Aims: To analyze the cytological significance of cell cannibalism in malignant effusion samples. Materials and Methods: A retrospective review of 100 cases of malignant effusion was done. These 100 cases included 50 cases of contiguous, local spread to pleural/ascitic fluid. The remaining 50 cases were of disseminated malignancy. Effusions due to hematolymphoid malignancies were excluded. Smears from these cases were assessed for the presence of cell cannibalism, tumor cell within a tumor cell. Results: The cannibalistic cells were more common in effusions with disseminated malignancy (nine out of 50 cases i.e. 18%) compared with cases of contiguous, local spread (two out of 50 cases i.e. 4%). Chi square test showed this difference to be statistically significant (x(2) 5.005, P=0.025). The majority of the cases were of carcinoma lung (6/11). Cytomorphologically, histiocytes displaying phagocytosis can simulate tumor cells and need to be distinguished. Conclusions: Presence of cell cannibalism in malignant effusions is more often an indicator of disseminated malignancy with secondaries and higher tumor stage. Furthermore, cannibalism may provide a reliable predictor of progression of tumor from primary to the metastatic site.