Hepatoid Adenocarcinoma of Lung Presenting as Unknown Primary with Cervical Lymphadenopathy: A Rare Case Report

Abstract

Hepatoid adenocarcinoma is a rare Alpha Fetoprotein (AFP) producing extrahepatic malignant tumour commonly seen in the stomach but can also arise from the ovary, endometrium lung. It is a rare type of adenocarcinoma with hepatocyte like histological differentiation and occurs outside the liver. In the lung, it is often presented as a bulky tumour, highly malignant, and associated with a poor prognosis. Early diagnosis and appropriate treatment options can result in long term survival. Here, authors reported a case of 58-year-old male patient, with no history of smoking presented as an Unknown Primary (UKP) with cervical and mediastinal lymphadenopathy which was later diagnosed histopathologically and confirmed by Immunohistochemistry (IHC) as Hepatoid Adenocarcinoma Lung (HAL) without any lesion in the lung on Computed Tomography (CT) chest. The serum AFP levels were normal. It expressed IHC markers Cytokeratin (CK7), CDX-2, Hep Par1 positivity, Thyroid Transcription Factor 1 (TTF-1) cytoplasmic positivity, and abnormally raised serum Carcinoembryonic Antigen (CEA). The patient was treated with definitive lower neck and mediastinal irradiation followed by adjuvant chemotherapy with five cycles of three weekly pemetrexed and carboplatin. Post treatment the serum CEA levels are decreasing and attained clinically complete response. The patient was in a close follow-up. To date, the review of literature about HAL didn’t showed any case presented as UKP with neck nodes without any lesion in the lung. The purpose of this case report was to present a new case of HAL with nodal metastasis, its unique histological findings, and its approach to diagnosis and treatment.