Tumor cell phagocytosis (cannibalism) in lung cancer: possible biomarker for tumor immune escape and prognosis

Background: Tumor cell phagocytosis (cannibalism) is rarely seen in lung carcinomas. Little is known about its underlying cellular pathogenesis and associated significance as tumor immune escape mechanism. Methodology: The cases of lung cancer diagnosed at department of Pathology, VPCI over 13-year period, 20072020 (n = 350) were retrospectively reviewed. The cases displaying cannibalism were correlated with their tumor morphology, coexisting inflammation, patient age at presentation, sex, stage/grade, and smoking status. Results: Cannibalism was identified in 10/350 (2.86%) cases of lung cancer. 9/10 (90%) were males and 1/10 (10%) was female. These patients ranged from 48-71 years of age and presented with history of chest pain, anorexia and weight loss. History of smoking was seen in 9/10 (90%) cases while 10% were non-smokers. Mass lesions were seen on CT scan and CT-guided fine needle aspiration cytology (FNAC) was performed. Cytopathology revealed squamous cell carcinoma (5/10, 50%), adenocarcinoma-3/10 (30%), adenosquamous carcinoma (1/10, 10%), and non small cell lung carcinoma (1/10, 10%). No association with small cell carcinoma was seen in our study. Background inflammation and infiltration of acute on chronic inflammatory infiltrate were seen in 6/10 or 60% cases. Conclusion: Lung cancers rarely show cannibalism, a tumor immune escape mechanism, even in advanced stage. This phenomenon correlates with squamous cell and adenocarcinoma morphology, tumor associated inflammatory infiltrate, and smoking status. It may be considered as a possible biomarker for tumor immune escape and poor prognosis.