BACKGROUND. Patients with noninvasive, small‐sized primary adenocarcinomas of the lung have excellent prognosis after lobectomy. Several researchers have suggested that limited resection could be an acceptable alternative for these patients. Therefore, a preoperative or intraoperative judgment of invasiveness would be one of the critical determinants of the surgical procedure in each case. Cytopathologic findings that can distinguish invasive from noninvasive adenocarcinomas remain to be elucidated. METHODS. Imprint smears were obtained from 60 resected adenocarcinomas with nonmucinous bronchioloalveolar features. Thirteen cytologic factors were evaluated: the presence of necrosis, fibrovascular tissue, proportion of macrophages, the presence of large tumor cell clusters, nuclear grooves, nuclear overlapping, variation in nuclear size, chromatin pattern, presence of a nucleolus, intranuclear inclusions, multinucleated cells, spindle cells, and mitosis. Each factor was examined by univariate analysis for correlation with the presence of histopathologic invasion. RESULTS. In the univariate analysis, 5 cytologic factors—presence of tumor cell clusters consisting of more than 50 tumor cells (P < .001), nuclear overlapping in more than 3 layers (P < .001), presence of nuclear grooves (P = .007), more than 3‐fold variation in nuclear size (P < .001), and 1 mitotic cell per 1000 tumor cells (P = .035)—were associated significantly with invasion. Among these, nuclear overlapping in more than 3 layers (P = .003) and more than 3‐fold variation in nuclear size (P = .005) were found to be independent predictive factors for invasion by multivariate analysis. CONCLUSIONS. Using imprint smears, the presence of invasion in small‐sized primary adenocarcinomas of the lung is predictable by the 2 above‐mentioned cytologic findings. Imprint smear cytology may effectively aid intraoperative judgement of invasion in cases where frozen section histology is difficult to interpret. Cancer 2006. © 2006 American Cancer Society.

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Signet-ring cell carcinoma (SRCC) and goblet-cell-type adenocarcinoma (GCA) are mucin-producing lung adenocarcinomas. Primary SRCC shows an aggressive clinical course, whereas GCA shows infrequent distant metastasis, but more frequent intrapulmonary metastases resembling lobar pneumonia. To distinguish SRCC from GCA, this study investigated the respective cytological features of these lesions. We selected 10 cases each of SRCC and GCA from the archival imprint smears. We assessed them for the following 10 cytological features. Necrosis/debris was observed in 60% of the SRCC and 90% of the GCA. A mucinous background was observed in 10% of the SRCC and 90% of the GCA. Significant inflammation was observed in none of the SRCC and 80% of the GCA. Stromal cluster was observed in 30% of the SRCC and 70% of the GCA. Nuclear overlapping was observed in 50% of the SRCC and in all of the GCA. Single tumor cells were observed in 80% of the SRCC and 10% of the GCA. Honeycomb-like cluster was observed in none of the SRCC and 80% of the GCA. Prominent nucleolus was observed in 50% of the SRCC and 40% of the GCA. Nuclear membrane irregularity was observed in 70% of SRCC and 60% of the GCA. Nuclear pleomorphism was observed in all of the SRCC and none of the GCA. The cytological features of SRCC were the presence of single tumor cells and nuclear pleomorphism, whereas that of GCA were the presence of abundant mucin and significant inflammation in the background, and a honeycomb-like cluster.

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