Abstract

Pure primary Signet-Ring Cell Carcinoma (SRCC) of lung is an extremely rare entity. Typically seen in nonsmokers, it is considered to be highly invasive, highly aggressive and carries a worse prognosis when compared to other types of lung tumors. Cytological identification of pulmonary SRCC is challenging and must be differentiated from both benign and malignant lesions. Here we describe a case of a 40-year-old immigrant Chinese male with a significant past medical history of smoking, who was found to have 2.7 cm lung nodule on CT scan. A subsequent CT scan two weeks later showed the original right lung nodule with no evidence of extra pulmonary lesions on the PET scan and the bone scan. Bronchoalveolar lavage and brushings, as well as fine needle aspiration, of the lung lesion revealed an adenocarcinoma with 100% signet ring cell morphology. Due to the lack of extra pulmonary malignancy according to radiographic evidence, the following immunocytochemistry work up on the cell block was performed in order to characterize the lesion as primary pulmonary SRCC: CK7, CK20, TTF-1, p63, CDX2, thyroglobulin, CD68, napsin A, PSA and PSAP. Subsequent excision biopsy was obtained, which revealed adenocarcinoma with 95% signet ring cell purity.

Keywords: Signet Ring Cell Adenocarcinoma; Lung; Cytomorphology; Immunohistochemistry