Prostate gland & seminal vesicles

• Atrophy and its less common subtype postatrophic hyperplasia often comprise small acini and are the most frequent histologic mimics of prostatic adenocarcinoma

• Benign prostate tissue with atrophy
• When associated with inflammation and increased Ki67 index, it has been termed proliferative inflammatory atrophy (PIA)

• ICD-9: 602.2 - atrophy of prostate
• ICD-10: N42.89 - other specified disorders of prostate

• Atrophy is a common incidental finding in prostate biopsy and prostatectomy and increases with age

• Can be partly reversed by prolactin (Reprod Biol Endocrinol 2021;19:94)
• Whether atrophy is a precursor to high grade prostatic intraepithelial neoplasia (HGPIN) and cancer has been controversial; atrophy with inflammation has some spatial association to low grade cancer (Int Urol Nephrol 2011;43:397, Hum Pathol 2014;45:54)

• Increases with age

• Diagnosis is by prostate biopsy or transurethral resection

• Atrophy correlates with serum total or free PSA elevation; for this reason, it may be desirable to report atrophy in a negative biopsy set (Abdom Imaging 2009;34:271)

• Atrophy can simulate cancer by Doppler transrectal ultrasound and on magnetic resonance spectroscopic imaging studies (Abdom Imaging 2009;34:271, Radiographics 2016;36:162)
• When cystic, can produce high signal intensity areas on T2 weighted imaging (Eur Radiol 2017;27:2095)

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• 4 subtypes have been categorized (Am J Surg Pathol 2006;30:1281):
  • Simple atrophy:
    • Characterized by its basophilic appearance at low magnification
    • Glands may be crowded or back to back with little intervening stroma
    • When associated with sclerosed stroma, the glands may assume a more angulated shape and infiltrative appearance
  • Simple atrophy with cyst formation:
    • Ballooning large acinar spaces
  • Postatrophic hyperplasia (PAH):
    • Postatrophic hyperplasia also appears basophilic at low power but often surrounds a dilated duct and is arranged in lobules of crowded acini
    • Normally has more mitotic figures than adjacent nonatrophic glands
  • Partial atrophy:
    • In contrast to simple atrophy and postatrophic hyperplasia, acini have a pale appearance and nuclei are more spaced apart

Contributed by Kenneth A. Iczkowski, M.D.

• Atrophic glands can occasionally be negative or have patchy staining for basal cell markers High molecular weight cytokeratin and p63 (Mod Pathol 2002;15:1302)
• AMACR should be negative in most instances but may be positive; in that event, the dual immunostain (prostate basal cell markers and AMACR) usually show at least focal basal cells but sometimes not (Histopathology 2004;45:218, Am J Clin Pathol 2006;126:849)

• Prostate, biopsies:
  • Benign prostatic tissue with focal / multifocal / diffuse atrophy

• Must distinguish from the atrophic variant of prostatic adenocarcinoma, which has these features:
  • Less cytoplasm, dilated lumens, macronucleoli in the majority of cells and absence of basal cells
  • Infiltrative growth between benign glands without atrophy
  • Usually coexists with usual type adenocarcinoma

Which of the following is true of prostatic atrophy?

1. It is a strong predictive finding for subsequent cancer detection
2. It is characterized exclusively by a small acinar pattern
3. It cannot be associated with increased serum prostate specific antigen (PSA)
4. It has no characteristic radiologic findings
5. It is mimicked by a variant of cancer

E. Atrophy is mimicked by a variant of cancer, called the pseudoatrophic variant. Atrophy is not a predictor of subsequent cancer detection (answer A) and may even lessen the chances of eventual cancer. Atrophy is not exclusive to small acini (answer B) and large acinar (cystic) types exist. Atrophy sometimes can be associated with increased serum prostate specific antigen (PSA) (answer C). Atrophy may have certain characteristic radiologic findings (answer D).

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Reference: Prostatic atrophy

What does the red staining AMACR signal indicate?

1. Lack of cytologic atypia rules out cancer, even when red AMACR signal is present
2. It indicates that some of these acini are suspicious for cancer
3. It indicates cancer
4. It indicates high grade prostatic intraepithelial neoplasia

A. This red signal is present in benign, nonatypical atrophic acini. Remember that AMACR / P504S can give false positive results and atrophy is one source of such results. The dual stain should be interpreted with caution, based on corresponding hematoxylin eosin findings. High grade PIN should be AMACR positive but would have atypia.

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Reference: Prostatic atrophy