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

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. The cases of lung cancer diagnosed at department of Pathology, VPCI over 13-year period, 2007-2020 (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. 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. 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.