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.
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.
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.
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.