Micropapillary components in a lung adenocarcinoma predict stump recurrence 8 years after resection: a case report

We report a rare case of lung adenocarcinoma in which micropapillary components were considered to cause stump recurrence. A woman in her fifties was diagnosed with lung cancer in the right middle lobe with invasion to the upper lobe, which was treated by a right middle lobectomy together with upper lobe partial resection. The cancer was pathologically diagnosed as adenocarcinoma and had a free surgical margin. There was no recurrence during the following 5 years and 8 months, and thus periodical surveillance, including computed tomography, was stopped. However, 2 years and 7 months after this, she was discovered to have an abnormal shadow on chest radiography, and a thorough examination revealed a 3-cm-sized tumor involving the previous surgical margin. Therefore, she underwent right upper lobectomy. We pathologically re-evaluated the first tumor and found that it was an adenocarcinoma with a micropapillary component in the periphery, 6mm away from the surgical margin. In addition, a few tiny clusters of tumor cells were found to be floating within the alveolar spaces near the margin. The first and second tumors showed almost the same histological mixture of components of adenocarcinoma and the same EGFR mutation. From these results, we concluded the second tumor was a stump recurrence originating from the first tumor resection. This case illustrates the importance of careful pathological investigation when an autosuture instrument is used for a partial resection in a case of lung adenocarcinoma with micropapillary components. In such cases, it is particularly important to clarify if micropapillary components are floating near a stump.