In order to examine selective lung
metastasis in
lung adenocarcinoma, 7 patients who had died due to
metastasis exclusively to the lung were analyzed. Because all of the
tumors had been well differentiated
adenocarcinoma, 21 cases of well differentiated
adenocarcinoma which had metastasized to both the lung and other distant organs were selected as controls. Histologically, 6 of the 7 study cases were
bronchiolo-alveolar carcinoma (BAC) of variable cytological type or
papillary adenocarcinoma with a thin fibrovascular stroma without apparent destruction of the alveolar wall. There was no difference in clinical findings or nuclear
DNA content (NDC) between the BAC and
papillary adenocarcinoma with thin fibrovascular stroma. The fibrovascular stroma in the study cases was significantly thinner than that in the control cases (P less than 0.01). Cytofluorometrically, the study cases had a significantly lower and less abnormal NDC than the control cases in terms of the mean NDC and
DNA histogram patterns (P less than 0.01 and P less than 0.05, respectively). On the basis of these findings, we conclude that 1) BAC can be classified within the same spectrum as well differentiated
papillary adenocarcinoma, and 2) selective lung
metastasis occurs in well differentiated
adenocarcinomas showing mild NDC abnormalities and having a thin fibrovascular stroma without apparent destruction of the alveolar wall.