The clinical and histologic profiles of primary lung carcinomas with signet-ring cell carcinoma (SRCC) components were analyzed. The SRCC components were seen in 39 cases (1.5%) of 2640 cases of surgically resected primary lung carcinomas. The patients' mean age was 54.6 years (range, 32-76 years), and the male-to-female ratio was 1.16:1.00. Twenty-six patients (66.7%) were smokers. The SRCC component was seen as part of an adenocarcinoma in 36 cases (acinar, 27 cases; mixed bronchioloalveolar and acinar, 9 cases) and as part of an adenosquamous cell carcinoma in 2 cases; one lesion consisted of only SRCC cells. The morphologic appearance of cancer nests containing SRCC was classified into three patterns: solid, tubuloacinar, and discohesive. Each case was composed of a varying proportion of these three patterns. The carcinomas with SRCC components were divided into two groups, according to those in which the SRCC component occupied <50% of the lesion (L-SRCC; n = 20) and those in which the SRCC component occupied > or = 50% of the lesion (H-SRCC; n = 19). The frequencies of blood vessel invasion, lymph vessel invasion, and lymph node metastasis were significantly higher in the H-SRCC group than in 1634 adenocarcinoma, and adenosquamous cell carcinomas (non-SRCC). The 5-year survival rates of patients non-SRCC, with l-SRCC, or with H-SRCC were 52.7%, 50%, and 28.4%, respectively. The 5-year survival rate of patients with H-SRCC and of patients without SRCC were significantly different. Based on these clinicopathologic characteristics, we classified primary lung carcinomas with SRCC components into the following two groups: 1) SRCC, in which the SRCC component occupies >or = 50% of the lesion, and 2) signet-ring feature, in which the SRCC components occupies <50% of the lesion.