Primary Signet Ring Adenocarcinoma of the Lung in a 34-Year-Old Nonsmoking Man

Background: Pulmonary carcinoma is a burdensome malignancy that has the third rank in prevalence among other cancers and is the leading cause of death in patients with cancer diagnosis. Signet ring morphology is encountered commonly in many sites like stomach, bladder, gallbladder and etc. Primary signet ring adenocarcinoma of the lung is a rare phenomenon, including about 5% of all surgically removed pulmonary adenocarcinoma. It should be distinguished from metastatic tumors. Case presentation: a 34-year-old nonsmoker man who referred to Babol Rohani Hospital with a onemonth history of nonproductive cough. Biopsy with CT scan guidance from groundglass opacities of the left lung revealed neoplastic cells with signet ring appearance infiltrating lung parenchyma. Immunohistochemistry (IHC) study revealed positivity of neoplastic cells for AE1/AE3, CK7, TTF1 and negativity for CK20, CDX2, and CD68. Conclusion: The signet ring feature of pulmonary adenocarcinoma has shorter survival, therefore, it is associated with poor prognosis. Immunohistochemistry (IHC) techniques provide the ability to originate tumor cells in these conditions.