Atypical small acinar proliferation

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Atypical small acinar proliferation
Diagnosis in short

Atypical small acinar proliferation - top-left of image. H&E stain.

Synonyms suspicious for prostate carcinoma

LM morphology of prostate carcinoma but less than 6 glands (major criteria for prostate carcinoma: abnormal architecture (increased gland density, usu. small circular glands, "infiltrative growth" pattern), basal cells lost, cytological abnormalities (nuclear enlargement, nucleoli); minor criteria for prostate carcinoma: nuclear hyperchromasia, wispy blue mucin, pink amorphous secretions, intraluminal crystalloid, amphophilic cytoplasm, adjacent HGPIN, mitoses)
LM DDx prostate adenocarcinoma, benign prostate
IHC AMACR +ve, CK34betaE12 -ve, p63 -ve, PSA +ve
Site prostate gland

Prevalence ~3-5% of prostate biopsies
Blood work +/-PSA elevated
Prognosis increased risk of prostate carcinoma
Other waffle diagnosis - used only on biopsy
Treatment re-biopsy, close follow-up

Atypical small acinar proliferation, abbreviated ASAP, is a small number of prostate glands that are abnormal and suspicious for carcinoma.

It is also known as suspicious for carcinoma.[1] ASAP is preferred as it does not contain the word carcinoma and, thus, cannot be misread as carcinoma, i.e. positive for malignancy.


  • It is a waffle diagnosis, i.e. it is not considered an entity with a distinct pathobiology.[2]
    • Analogous to ASCUS on a pap test.
  • ASAP should be used sparingly.
    • One benchmark is < 3-5% of biopsies.[1]
  • Never diagnosed on excision, i.e. prostatectomy specimen.
  • Cancers diagnosed in biopsies after ASAP are not more frequently clinically significant than cancers diagnosed after a diagnosis of benign or HGPIN.[3]

Association with adenocarcinoma


  • ASAP is generally considered an indication for re-biopsy;[5] in one study[6] 41/42 (~98%) of urologists considered it a sufficient reason to re-biopsy.



  • Atypical appearing acini - see criteria for prostate adenocarcinoma.
  • Limited extent - key feature.
    • Less than six glands.†


  • Deeper cuts didn't yield anything - important.
  • † There is no agreed upon minimum number of glands; however, one paper suggests that agreement among experts is low with 5 or less glands.[7]




Usually stains like cancer:

  • AMACR +ve.
  • CK34betaE12 -ve.
  • p63 -ve.


  • Often not contributory.


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C. Prostate, Left Base:
- Atypical prostatic glands, suspicious for microfocus of adenocarcinoma.

Block letters


See also


  1. 1.0 1.1 THvdK. 19 June 2010.
  2. Flury SC, Galgano MT, Mills SE, Smolkin ME, Theodorescu D (January 2007). "Atypical small acinar proliferation: biopsy artefact or distinct pathological entity". BJU International 99 (4): 780-5. PMID 17378841.
  3. Wiener, S.; Haddock, P.; Cusano, J.; Staff, I.; McLaughlin, T.; Wagner, J. (Dec 2017). "Incidence of Clinically Significant Prostate Cancer After a Diagnosis of Atypical Small Acinar Proliferation, High-grade Prostatic Intraepithelial Neoplasia, or Benign Tissue.". Urology 110: 161-165. doi:10.1016/j.urology.2017.08.040. PMID 28888752.
  4. Leite KR, Camara-Lopes LH, Cury J, Dall'oglio MF, Sañudo A, Srougi M (June 2008). "Prostate cancer detection at rebiopsy after an initial benign diagnosis: results using sextant extended prostate biopsy". Clinics 63 (3): 339–42. PMID 18568243.
  5. Bostwick DG, Meiers I (July 2006). "Atypical small acinar proliferation in the prostate: clinical significance in 2006". Arch. Pathol. Lab. Med. 130 (7): 952–7. PMID 16831049.
  6. Rubin MA, Bismar TA, Curtis S, Montie JE (July 2004). "Prostate needle biopsy reporting: how are the surgical members of the Society of Urologic Oncology using pathology reports to guide treatment of prostate cancer patients?". Am. J. Surg. Pathol. 28 (7): 946–52. PMID 15223967.
  7. Van der Kwast, TH.; Evans, A.; Lockwood, G.; Tkachuk, D.; Bostwick, DG.; Epstein, JI.; Humphrey, PA.; Montironi, R. et al. (Feb 2010). "Variability in diagnostic opinion among pathologists for single small atypical foci in prostate biopsies.". Am J Surg Pathol 34 (2): 169-77. doi:10.1097/PAS.0b013e3181c7997b. PMID 20061936.