Diagnostic value of bronchial cast sign and string of beads sign in peripheral small cell lung cancer

Abstract Purpose To evaluate the significance of the bronchial cast sign (BCS) and the string of beads sign (SBS) in the differential diagnosis among peripheral small cell lung cancer (pSCLC), peripheral lung adenocarcinoma (pLUA) and peripheral lung squamous cell carcinoma (pLSCC), and to discuss the formation mechanism of the two signs in pSCLC. Methods and materials Pathologically confirmed 78 cases of pSCLC, 69 cases of pLUA and 33 cases of pLSCC were included in this study. The positive rates of BCS, SBS, mediastinal lymph node metastasis and mediastinal lymph nodes larger than primary lung lesions are calculated and analyzed in pSCLC group, pLUA group and pLSCC, respectively. Results The positive rate of BCS, SBS, mediastinal lymph node metastasis and mediastinal lymph nodes larger than primary lung lesions were 23.1%, 12.8%, 80.8% and 53.8% in the 78 pSCLC patients, respectively. Mediastinal lymph nodes were all larger than primary lung lesions in the pSCLC with SBS. There were no BCS or SBS observed in the 69 cases of pLUA, in which 25 cases (36.2%) had mediastinal lymph node metastasis and 2 cases (2.9%) shown the mediastinal lymph nodes were larger than the original lung lesions. The positive rates of BCS, SBS, mediastinal lymph node metastasis and mediastinal lymph nodes larger than primary lung lesions were 6.1%, 2.8%, 39.4% and 16.7% of the total 33 cases with pLSCC, respectively. Conclusion SBS and BCS in CT images reflect the biologic characters of pSCLC at a certain level and show noteworthy clinical value in differential diagnosis of pSCLC, pLUA and pLSCC. However, the two signs should be combined with other CT signs of pSCLC and mediastinal lymph node size.