Conflicting immunohistochemistry and metabolic imaging parameters in adenocarcinoma lung showing elevated serum CA 19-9 with immunonegative TTF1 and Napsin A

Abstract

Lung carcinoma is the most common and lethal malignancy in men. Non-small cell lung carcinoma is more aggressive than small cell lung carcinoma and often presents in advanced stage with metastasis. Cytology, histopathology, immunohistochemistry and metabolic imaging play an important role in classifying lung carcinomas. TTF 1 and Napsin A are highly sensitive and specific for adenocarcinoma lung, but the sensitivity and specificity decreases in high grade tumours. Elevated serum CA 19-9 tumour marker is not always related to pancreatico-biliary adenocarcinomas. It can be positive in adenocarcinoma lung and its elevation confers poor prognosis. Quintessential role of metabolic imaging like 18 F-FDG PET CT scan in high grade carcinomas is well known. With the advent of targeted therapy, molecular and receptor studies of EGFR, ROS 1 and ALK gene rearrangement becomes mandatory in all lung adenocarcinomas. Hence, both oncologist and pathologist should diagnose advanced stage tumours without bias with good clinical, radiological and pathological correlation.