Primary signet-ring cell carcinoma of the lung: a report of 2 cases.

Background: Signet-ring cell carcinoma is a distinct subtype of mucin-producing adenocarcinoma that originates in various organs, particularly the stomach. However, primary signet-ring cell carcinoma of the lung is an extremely rare condition. The preoperative identification of signet-ring cells by cytologic examination is vital because signet-ring cell carcinoma of the lung has been reported to have a worse prognosis than ordinary adenocarcinoma. In this study, we present 2 cases of primary signet-ring cell carcinoma of the lung in conjunction with their cytomorphologic features.

Cases: Bronchial brush and wash samples were obtained from the lungs of a 63-year-old woman and a 65-year-old man for the evaluation of lung tumors. Examination of the bronchial samples revealed many large clusters of atypical cells containing abundant intracytoplasmic mucin. Although the clusters were equivocal in the first case, the presence of more atypical cell clusters led to the diagnosis of adenocarcinoma.

Conclusion: Signet-ring cell carcinoma should be considered when many atypical round cells with abundant intracytoplasmic mucin--namely, signet-ring cells--are observed along with adenocarcinomatous cells.