Small nodules (≤ 6 mm in diameter) of multiple primary lung cancers: prevalence and management.

BACKGROUND: Synchronous multiple primary lung cancers associated with small non-dominant nodules are commonly encountered. However, the incidence, follow-up, and treatment of small non-dominant tumors have been but little studied. We explored the prevalence and management of small non-dominant tumors and factors associated with interval growth. METHODS: This observational, consecutive, retrospective single-center study enrolled patients diagnosed with synchronous multiple primary lung cancers and small non-dominant tumors (≤ 6 mm in diameter) who underwent resection of the dominant tumor. The incidence, follow-up, and management of small non-dominant tumors and predictors of nodule growth were analyzed. RESULTS: There were 88 patients (12% of all lung cancer patients) with pathological diagnoses of synchronous multiple primary lung cancers. A total of 131 (18%) patients were clinically diagnosed with at least one small (≤ 6 mm in diameter) multiple primary lung cancer non-dominant tumor. 94 patients with 125 small-nodule non-dominant tumors clinically diagnosed as multiple primary lung cancers were followed-up for at least 6 months. A total of 29 (29/125, 23.2%) evidenced small pulmonary nodules (≤ 6 mm in diameter) that exhibited interval growth on follow-up computed tomography (CT). On multivariate analysis, a part-solid nodule (compared to a pGGN) (OR 1.23; 95% CI 1.08-1.40) or a solid nodule (compared to a pGGN) (OR 3.50; 95% CI 1.94-6.30) predicted small nodule interval growth. CONCLUSION: We found a relatively high incidence of multiple primary lung cancers with small non-dominant tumors exhibiting interval growth on follow-up CT, suggesting that resection of non-dominant tumors at the time of dominant tumor resection, especially when the nodules are part-solid or solid, is the optimal treatment.

Significance of nonmucinous lepidic component with mild nuclear atypia in the discrimination of multiple primary lung cancers from intrapulmonary metastases.

The distinguishing of intrapulmonary metastases from multiple primaries is of great clinical importance. Although comprehensive histological assessment (CHA) was recommended for addressing this problem, the limitations of CHA have been addressed. We hypothesized that a nonmucinous lepidic component with mild nuclear atypia (NLCMA) may be one of the important sign suggesting primary lesions. In this study, we measured the value of NLCMA in distinguishing multiple primaries from intrapulmonary metastases. We retrospectively analyzed a cohort of 54 patients with 116 lesions (70 comparisons). Intrapulmonary metastases and multiple primaries were differentiated on the basis of CHA (Method I) and CHA combined with the assessment of NLCMA (Method II), respectively. Then, the results of two methods were compared with survival analysis. 33 cases were defined as multiple primaries and 21 cases as metastases by Method I, while 41 cases as multiple primaries and 13 cases as metastases by Method II. On univariate analysis, there was a better DFS in patients with a tumor ≤ 3 cm (P=0.012), female gender (P=0.011), highest N0 (P=0.002), absent micropapillary (P=0.013), multiple primaries (P=0.008 by method I, P < 0.001 by method II). A multivariate analysis adjusting for gender, tumor size, micropapillary and multiple primaries/metastases (by methodI and method II, respectively) indicated that multiple primaries (by method II) was an independent predictors for DFS. The presence of NLCMA may indicate that a lesion should be defined as primary in multifocal adenocarcinoma.