Benign ectopic prostatic glands in subvesical skeletal muscle. A lesion resembling carcinoma

In physiological instances, the prostatic acini may be intermingled with striated muscle fibers in the apex and in the anterolateral subcapsular areas of the prostate. We report an unusual lesion composed of benign prostatic glands, which were scattered between skeletal muscle fibers beneath the bladder submucosa. A 55-year-old man underwent four transurethral resections and radiation therapy for a urothelial carcinoma of the urinary bladder. Subsequently a cystectomy was performed. In the resection specimen, the prostate specific antigen-positive glands were found among the skeletal muscle bundles close to the bladder submucosa. They were seen as small groups of haphazardly scattered or isolated glands mimicking an infiltrative pattern of a prostatic adenocarcinoma. Prominent nucleoli in some glands further contributed to the worrisome appearance of the lesion. However, the high molecular weight cytokeratin 34 beta E12 exhibited basal cell layers of the glands, and the subsequent course of disease confirmed the benign nature of the lesion. The juxtaposition of the prostatic acini with the skeletal muscle out of the apex and the anterolateral subcapsular areas of the prostate should be included in the differential diagnosis of prostatic carcinoma in urinary bladder and prostate biopsies.