Neutrophil phagocytosis by tumor cells--a cytological study

Cell cannibalism is defined as the ability of a cell to phagocytose another cell. Malignant tumor cells may develop phagocytic property and demonstrate phagocytosis of own cells or cells of other series like neutrophils and lymphocytes. We report 11 cases in which the tumor cells showed evidence of neutrophil phagocytosis/emperipolesis on FNAC smears. Cases of malignancies diagnosed on FNA over a period of 1 year were retrieved, and smears were examined for neutrophil phagocytosis by tumor cells. These cases were classified according to type and differentiation of malignancy. The cytomorphological features and background inflammation were also studied at both primary and metastatic site. Of 362 malignant cases diagnosed on FNA smears, in 11 cases (3.09%), tumor cells showed neutrophil phagocytosis. The background showed increase in polymorphs in all cases. All the cases were associated with metastasis at presentation and were high-grade tumors cytologically. There were three cases of anaplastic carcinoma, two cases of adenocarcinoma, two cases of carcinoma breast, two cases of anaplastic non-Hodgkins lymphoma, one case each of squamous cell carcinoma and small cell carcinoma from larynx and lung, respectively. Phagocytic activity by tumor cells is uncommon and usually seen in high-grade/poorly differentiated malignancies. It is frequently associated with metastatic disease. On cytology smears, true phagocytosis of neutrophils by tumor cells has to be distinguished from superimposed inflammatory cells from the background. The tumor cells also need to be distinguished from histiocytes displaying phagocytosis.