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Significance of Atypical Small Acinar Proliferation (ASAP) in Prostate needle biopsy

Posted May 25 2009 11:29am
Many time while reporting prostate needle biopsy, we come across features, which are suspicious for malignancy, but hinder a definitive diagnosis of carcinoma, because of concern about over diagnosis. These are the cases, which are labelled as ASAP, -atypical small acinar proliferation.

Diagnostic criteria for ASAP :
For pathologists, 3 questions need to be answered before the diagnosis of cancer in a small lesion• Would you be absolutely confident of this biopsy diagnosis if it were followed by a negative radical prostatectomy?
• Would another colleague pathologist agree with the diagnosis of cancer?
• Can you confidently support the diagnosis of adenocarcinoma based solely on this biopsy?

If the answer to any of these questions is “No,” then use of the more conservative diagnosis of ASAP is recommended.

Reasons for the Diagnosis of ASAP are :

  • Small number of acini in the focus of concern.
  • Small focus size, average 0.4 mm in diameter.
  • Loss of focus of concern in deeper levels.
  • Distortion of acini raising concern for atrophy.
  • Lack of convincing features of cancer (insufficient nucleomegaly or nucleolomegaly).
  • Foamy cytoplasm raising concern for foamy gland carcinoma.
  • Conflicting immunohistochemical findings.

Significance of ASAP. -

Prostate cancer is found in up to 60% of repeat biopsies after the diagnosis of ASAP. Thus
ASAP in a biopsy is a significant predictor for concurrent or subsequent cancer. The high predictive value of atypical small acinar proliferation (ASAP) for subsequent adenocarcinoma indicates a need for repeat biopsy.



References
1. Borboroglu PG, Sur RL, Roberts JL, et al. Repeat biopsy strategy in patients with atypical small acinar proliferation or high grade prostatic intraepithelial neoplasia on initial prostate needle biopsy. J Urol. 2001;166:866–870.
2. Cheville JC, Reznicek MJ, Bostwick DG. The focus of “atypical glands,suspicious for malignancy” in prostatic needle biopsy specimens: incidence,histologic features, and clinical follow-up of cases diagnosed in a community practice. Am J Clin Pathol. 1997;108:633– 640.
3. Iczkowski KA, Bassler TJ, Schwob VS, et al. Diagnosis of “suspicious for malignancy” in prostate biopsies: predictive value for cancer. Urology.1998;51:749 –757; discussion 757–748.
4. Isabelle Meiers, at el. Atypical Small Acinar Proliferation in the prostate :Pathology Case reviews • Volume 13, Number 4, July/August 2008;13: 129–134
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