KLK3 and acinar cell carcinoma: Since they originate from the basal cell layer, other than secretive, glandular epithelium, the almost or true negative Prostate-specific antigen (PSA) immunohistochemical staining is one of the usual features of ACC/BCC, except for some positive cases, especially in mixed-form ACC/BCC plus acinar adenocarcinoma [12,13].