A case report of primary signet ring cell carcinoma of the lung: imaging study and literature review.

Signet ring cell carcinoma (SRCC) is a subtype of adenocarcinoma with characteristics of strong invasion and a poor prognosis. While it can occur in various organs, including the stomach, colon, esophagus, bladder, prostate, pancreas, and breast, primary lung SRCC is rare, and most SRCC found there are from gastrointestinal metastasis. Reports on primary lung SRCC are few and the aim of this study is to describe the imaging, histopathological, and immunohistochemical characteristics of a case of primary lung SRCC in our hospital. A 68-year-old female with no smoking history was admitted with recurrent cough, chest pain, and dyspnea of 2 months duration. Computed tomographic (CT) chest showed multiple solids nodules of different sizes and mass in the left upper lobe, lower lobe, and subpleural region. Multiple enlarged lymph nodes were seen in the mediastinum and left hilum. The aim of this paper is to improve the understanding of this tumor. A literature review identified 15 cases of primary lung SRCC with available CT imaging. Except for two patients with multiple ground glass nodules and multiple small nodules, the rest were solid, and ranged in size from 1.0 to 8 cm. Only one patient had a cavity in the solid lesion. Immunohistochemical stains for thyroid transcription factor-1 (TTF-1) (13/13) and CK7 (12/12) showed positive reaction in all cases evaluated, and napsin A (3/4) were also positive, while all cases including CK20 (12/12) and CDX2 (6/6) were negative.