New primary malignancy masquerading as metastatic prostate adenocarcinoma

In the management of patients with prostate cancer, the development of new radiographic findings can mimic progression of the disease, thereby triggering changes in treatment. Typically, clinicians evaluate additional parameters, such as symptoms and prostate specific antigen (PSA) levels, for further evidence of disease progression. In the absence of additional findings, for example, elevated PSA, the possibility of an additional malignancy should be considered and evaluated. We present three cases of patients undergoing treatment for prostate adenocarcinoma and discovered on imaging to have findings suggestive of disease progression, but ultimately found to be a new primary malignancy. Our cases suggest that, in patients with prostate cancer, the appearance of new lymphadenopathy or bone lesions cannot be assumed to solely represent progression of the prostate cancer and warrant further investigation, especially in the presence of stable PSA levels.