[A case of primary intrapulmonary thymoma: its entity and the problem of lymph node dissection].

Primary intrapulmonary thymomas are defined as primary thymomas arising in an intrapulmonary location without an associated mediastinal component, and they are very rare. A total of 20 cases have been reported only sporadically in the English literature since 1951. We reported the case of 41-year-old woman who had a 3.5 x 3.0 x 3.0 cm lower right lobe mass with nodal metastasis that extended over the left atrium. We also summarized the clinicopathological features of a total of 21 cases and discussed the problems involved with diagnosis, pathogenesis and treatment. Knowledge of the biological behavior of primary intrapulmonary thymomas is limited because of their rarity. In particular, the issue of the need for lymph node dissection has not been adequately discussed. In this case, pathohistological examination revealed that the routes of lymphatic spread and the sites of noda metastases from primary intrapulmonary thymoma resemble those of primary lung cancer. Therefore, systematic mediastinal lymph node dissection according to the lymph node map for primary lung cancer should be recommended for malignant cases.