Pulmonary adenocarcinoma with intestinal-type differentiation

A 44-year-old woman with a long history of smoking presented with a single lung mass detected on routine chest radiographs. There were no other known primary tumors. Light microscopy showed a mucin-producing adenocarcinoma of bronchioloalveolar type. Furthermore, no gastrointestinal primary has been discovered 18 months after discovery of the lung tumor. Electron microscopy revealed that tumor cells had microvilli containing abundant microfilamentous, dense-core rootlets that showed long extensions into apical cytoplasm. The microvilli were capped by numerous glycocalyceal bodies. These findings are similar to the ultrastructural features previously described as being specific for gastrointestinal adenocarcinomas metastatic to lung. The current case, however, suggests that the findings of glycocalyceal bodies and microvillous dense-core rootlets are not helpful in distinguishing between primary and metastatic lung adenocarcinomas.