Adenocarcinoma originating in the anterior mediastinum diagnosed by endobronchial ultrasound-guided transbronchial cryobiopsy: a case report

The patient was a 73-year-old woman, who had never smoked, and who had a history of left breast cancer that was treated with surgery followed by radiotherapy. Chest radiography revealed an abnormal shadow in the mediastinum (Fig. 1a). There were no notable physical findings or abnormal values of various tumor markers.

Chest contrast-enhanced computed tomography (CT) performed prior to ablation therapy for atrial fibrillation showed a mass with a maximum diameter of 5.2 cm in the anterior mediastinum. The mass was in extensive contact with the sternum on the ventral side and partly with the trachea on the dorsal side between the brachiocephalic and left common carotid arteries (Fig. 1b). ¹⁸F-fluorodeoxyglucose-positron emission tomography (FDG-PET) showed high FDG uptake in the mass and sternal infiltration but no significant uptake elsewhere (Fig. 1c). Two CTNBs were performed on the mass, but a definitive diagnosis was not made because of severe crush artifacts (Fig. 2a). We then performed EBUS-cryobiopsy to diagnose the lesion.

Using a linear EBUS bronchoscope (BF-UC290F, Olympus, Japan), the lesion was delineated from the trachea while observing the brachiocephalic and left common carotid arteries as merkmals, and a 22-gauge needle (NA-U401SX, Olympus, Japan) was used to create a small tract in the tracheal wall while collecting specimens with EBUS-TBNA [2]. Subsequently, EBUS-cryobiopsy was performed four times with freezing for around five seconds each time by inserting a 1.7-mm cryoprobe (20402–410, Erbe Elektromedizin GmbH, Germany) into the lesion through the tract, which was completed without complications (Fig. 3). EBUS-cryobiopsy yielded sufficient specimen volume with minimal crushing. Histopathological findings revealed proliferating tumor cells with chromatin-enriched micronuclei that formed scattered small foci against a background of extensive fibrous connective tissue with hyaline changes, indicating adenocarcinoma (Fig. 2b). The immunohistochemical staining features were distinct from those of the past breast cancer and thymic epithelial tumors, although HNF4α, CDX2, and CK20 were positive, which suggested a gastrointestinal tumor (Fig. 2c). However, it was difficult to morphologically determine whether the metastasis originated from a gastrointestinal tumor, and the systemic examination was negative for the presence of a gastrointestinal tumor. The tumor was diagnosed as a rare adenocarcinoma originating in the anterior mediastinum.

The patient underwent chemotherapy without any late complications of EBUS-cryobiopsy.