Cowper's gland hyperplasia: A potential pitfall at MRI of the prostate.

MRI features are presented in a multicenter retrospective series of five patients with a unilateral masslike lesion seen in the genitourinary diaphragm at MRI performed for known or suspected prostate cancer. In all cases, the lesion appeared as an encapsulated 1.3 to 3.0 cm mass of heterogeneous low or intermediate T2 signal intensity in the genitourinary diaphragm, and targeted biopsy demonstrated benign Cowper's gland tissue. This entity is a potential imaging pitfall that could result in a diagnosis of an exophytic nodule of benign prostatic hyperplasia or local spread of prostate cancer. We present these cases to facilitate correct identification of Cowper's gland hyperplasia as an occasional finding at MRI of the prostate.