Acinar adenocarcinoma (AAC) of the prostate is a tumor, which comprises a large part of prostatic malignancies and which can be confused with many lesions, benign and malignant. We aimed to discuss a prostatic AAC case, due to its morphology mimicking the adenoid basal cell carcinoma (ABCC) of the prostate, in the light of literature data, with particular emphasis on differential diagnosis criteria and confusing morphological characteristics.

Our case is a 74-year-old male patient who presented at the clinic with signs of urinary obstruction. The patient's, total PSA value was 9.32 ng/ml and free PSA value was 5.07 ng/ml. He was diagnosed as AAC upon histopathologic examination of his prostatic tru-cut needle biopsy. However, the following examination of the prostate trans-urethral resection material indicated areas consistent with ABCC. Then immunohistochemical analysis, the case was diagnosed as cribriform AAC. In routine control 9 month after diagnosis the patient had bone pains. Therefore bone scintigraphy was performed. The result of bone scintigraphy was degenerative changes on both knees, suggesting metastasis.

Although AAC of the prostate is the most common and the most easily diagnosed tumor of the prostate, it poses serious diagnostic problems when it is poorly differentiation. In some cases, morphological signs may not be sufficient in themselves for correct diagnosis, which should necessarily be supported and confirmed by immunohistochemical data.