Mediastinal mass mimicking a tumor in a patient with bladder cancer after Bacillus Calmette-Guerin treatment.

We describe the case of a 78-year-old male with bladder cancer who developed a mediastinal mass after intravesical immunotherapy with live Mycobacterium bovis BCG. The clinical diagnosis was mediastinal tumor suggestive for lymphoma. However, cultures of the biopsy specimens grew an acid-fast organism, which was identified as M. bovis BCG. To the best of our knowledge, this is the first reported case in which a post-instillation BCG infection induced a mediastinal mass that mimicked a tumor in a patient with bladder cancer.