{'fraction_non_alphanumeric': 0.02247191011235955, 'fraction_numerical': 0.0044943820224719105, 'mean_word_length': 5.194444444444445, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Superior vena cava aneurysm: an unusual mediastinal mass.

Superior vena cava aneurysms are rare mediastinal vascular lesions. Aneurysms are classified as fusiform and saccular, with the latter being rarer than the former. We report the case of an asymptomatic 75-year-old woman who presented with a superior mediastinal mass. She underwent chest computed tomography angiography, which demonstrated a saccular aneurysm in the superior vena cava.