Prostate gland & seminal vesicles
Benign mimickers of carcinoma
Adenosis / atypical adenomatous hyperplasia


Topic Completed: 15 April 2021

Minor changes: 15 April 2021

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PubMed Search: Adenosis [title] prostate

Cristina Magi-Galluzzi, M.D., Ph.D.
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Cite this page: Magi-Galluzzi C. Adenosis / atypical adenomatous hyperplasia. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/prostateadenosis.html. Accessed April 18th, 2021.
Definition / general
Essential features
  • Benign lobular proliferation of small crowded glands
  • Similar to prostatic adenocarcinoma; in adenosis, cells may show small or medium size nucleoli, crystalloids, intraluminal secretions, minimal infiltration and positive immunostaining for AMACR (racemase)
  • In contrast to prostatic adenocarcinoma, in adenosis, glands have more pale cytoplasm, merge with adjacent benign glands, commonly have corpora amylacea (Am J Surg Pathol 1994;18:863, Surg Pathol Clin 2008;1:1)
  • Basal cells can be identified on H&E slides or with immunohistochemistry for p63, cytokeratin 5/6 or HMWCK (Pathology 2013;45:251)
  • AMACR (racemase) can be focally or diffusely expressed in up to 18% of cases of adenosis (Am J Surg Pathol 2002;26:921)
  • Lack of ERG expression in adenosis supports the notion that it is not a precursor lesion of adenocarcinoma (Hum Pathol 2013;44:1895)
Terminology
ICD coding
  • ICD-10: N40.2 - nodular prostate without lower urinary tract symptoms

Epidemiology
  • 2 - 20% of transurethral resections of the prostate, 1% of prostate needle biopsies
Sites
Pathophysiology
Clinical features
  • Morphologic variant of benign crowded glands, a mimicker of low grade prostatic adenocarcinoma
  • Does not have clinical implications
Diagnosis
  • Detected on needle biopsy or transurethral resection
Radiology description
  • Multiparametric magnetic resonance imaging (mpMRI) may be difficult to interpret because it shows overlapping features with low grade prostatic adenocarcinoma (Eur Radiol 2017;27:2095)
Prognostic factors
  • Not a precursor lesion of prostatic adenocarcinoma (Hum Pathol 2013;44:1895)
  • Comparative genomic hybridization and multiplex PCR did not find common alterations between adenosis and accompanying cancer foci and concluded that adenosis should not be considered as an obligate premalignant lesion (Int J Oncol 2005;26:267)
  • Diffuse adenosis of the peripheral zone should be considered a risk factor for prostate cancer (Am J Surg Pathol 2008;32:1360)
Case reports
Treatment
  • Treatment not needed
Microscopic (histologic) description
Microscopic (histologic) images

Contributed by Cristina Magi-Galluzzi, M.D., Ph.D.
Well circumscribed nodule

Well circumscribed nodule

Mixed small and large acini

Mixed small and large acini

Basal cells

Basal cells

Crowded glands

Crowded glands

Bland nuclear features

Bland nuclear features

Fragmented basal cells

Fragmented basal cells

Positive stains
  • Basal cell markers (p63, CK5/6 and HMWCK) are positive in a patchy fashion (discontinuous staining; mixture of glands with and without basal cell layer) (Pathology 2013;45:251)
Negative stains
Molecular / cytogenetics description
Sample pathology report
  • It is not recommended to report adenosis
  • Prostate, needle biopsy or transurethral resection:
    • Benign prostatic tissue
Differential diagnosis
  • Low grade (Gleason score 3 + 3 = 6, grade group 1) prostatic adenocarcinoma:
    • Cytologic atypia, including prominent nucleoli and lack of basal cells
  • Partial atrophy:
    • Glands are partially atrophic with undulating luminal surface with papillary infolding; cytologic features are benign
Board review style question #1

Which of the following statements is true about the lesion depicted above?

  1. Atypical small acinar proliferation, favor benign
  2. Atypical small acinar proliferation, suspicious for malignancy
  3. Benign small acinar proliferation
  4. Prostatic carcinoma, Gleason score 3 + 3 = 6
Board review style answer #1
C. Benign small acinar proliferation. This is an example of adenosis (atypical adenomatous hyperplasia) with small acini lacking cytologic atypia and retaining basal cells.

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Reference: Adenosis / atypical adenomatous hyperplasia
Board review style question #2
Which of the following statements is true about adenosis?

  1. A fragmented and discontinuous basal cell layer is present
  2. AMACR is always negative
  3. It is a precursor lesion of prostatic adenocarcinoma
  4. More commonly in the peripheral zone
Board review style answer #2
A. A fragmented and discontinuous basal cell layer is present. Adenosis more commonly involves the transition zone; AMACR can be focally or diffusely expressed in up to 18% of cases of adenosis. Adenosis is not a precursor lesion of prostatic adenocarcinoma.

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Reference: Adenosis / atypical adenomatous hyperplasia
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