Atypical small acinar proliferation of prostate

This code describes a prostate biopsy finding characterized by small, crowded acini with some architectural and cytologic atypia, but insufficient to definitively diagnose adenocarcinoma. It represents a borderline lesion that may be a precursor to prostate cancer or a benign mimicker.

Assign this code when pathology reports explicitly state "atypical small acinar proliferation" (ASAP) or "atypical glandular proliferation suspicious for malignancy" in prostate biopsy specimens. This finding typically prompts further investigation, such as repeat biopsy or close surveillance.

• Do not use this code for definitive diagnoses of prostate cancer (e.g., adenocarcinoma); those have specific malignancy codes.
• Distinguish ASAP from high-grade prostatic intraepithelial neoplasia (HGPIN), which is coded separately.
• Ensure the pathology report clearly indicates ASAP and not just general "atypia" without further specification.