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AMACR Staining

Posted 02/06/07

Immunohistochemistry and Prostate Cancer

The immunohistochemistry laboratory has recently added "double staining" to its repertoire. This technique has special application when applied to the diagnosis of prostate cancer using both HMW keratin and the rasemace AMICAR.

α Methylacyl coA racemase (AMACR)

  • Enzyme important in branched fatty acid metabolism.
  • Xu et al (2000) identified specificity of expression in prostate ca by cDNA microarray library subtraction.
  • Jiang et al (2001) first published using monoclonal antibody (P504S) on tissue sections.
Table 1: Summary of Immunohistochemical Studies for the Discovery of P504S/AMACR as a Prostate Cancer Marker
References Antibodies Specimens Sensitivity Specificity
Jiang, et al (34) Monoclonal Ab 207 clinical cases 100%(n=137) 88% (n=194)
Rubin, et al (35) Polyclonal Ab 342 TMAs and 94 needle biopsies  97% (n=94) 100%(n=94)
Lou, ct al (36) Polyclonal Ab 168 CaP cases with standard slides and TMAs 96%(n=142) 97%(n=144)
Beach, et al (37)  Monoclonal Ab 405 clinical specimens 82%(n=186) 79% (n=377)
  • Sensitivity ranges from 100%-82%
  • Specificity ranges from a 100%-79% 
  • Beach et al showed “faint, non-circumferential” luminal staining seen in 21% of 377 benign lesions. 
  • However, also noted that circumferential staining was most specific pattern and “almost never associated with the benign prostate tissue”. 
  • No positive staining seen in post atrophic hyperplasia, transitional metaplasia, basal cell hyperplasia. 
HMW KER AMACR COMMENT
+pos -neg Benign
+pos +pos HGPIN, adenosis, “cancerization” of glands, some benign glands
-neg +pos Malignant
-neg -neg Benign or malignant; rare (< 6%)**

** Hypernephroidand “atrophic” types of prostate cancer have a greater chance of being "-neg".
POST RADIATION THERAPY
  • AMACR remains expressed.
    - - one study has shown down regulation in PRT cancers proportional to the extent of treatment effect.
  • AMACR expression unaffected by hormone manipulation.
HGPIN

In a study of 4000 HGPIN glands from 140 radical prostatectomies:

  • 90% of the cases were positive
  • 41.5% of individual glands involved with HGPIN were positive
    - - Positive rate higher in gland adjacent to cancer (<5 mm)
AMACR IN ADENOSIS/AAH
  • Negative 33/40 (82.5%)
  • Focal weak staining in 4/40 (10%)
  • Diffuse positive in 3/40 (7.5%)
  • Important to use both stains together (Yang et al, AJSP 2002;26:921-5.)
AMACR IN BENIGN CONDITIONS
  • Typically no staining.
  • When expressed, almost always focal, weak and noncircumferential.
    - - Fine granules (requires high mag)
    - - Negin atrophy, basal cell hyperplasia, inflammatory glands, urothelialepithelium/metaplasia and most AAH
    - - Nephrogenicadenoma is POS!
Final Diagnosis Resolved by Both Stains, No.(%) Unresolved After Both Stains, No.(%) Total, No. (%)
Benign 12   12 (29)
High-grade PIN 4   4 (10)
Cancer 15   15 (37)
ASAP   9 9 (22)
No agreement   1 1 (2)
Subtotal 31 (76) 10 (24) 41 (100)
* Adapted with permission from Jiang et al. 13 Not allowing disagreement between benign and malignant; half-step disagreements (cancer-ASAP or ASAP-benign) were acceptable. PIN indicates prostatic intraepithilial neoplasia. No entry indicates not applicable. (Iczkowski et al, Archives Pathol Lab Med; 2006:130 835)
click for larger image in new window
Infiltrating tumor (in red) between benign glands.		 click for larger image in new window
High grade PIN with surrounding infiltrating tumor.		 click for larger image in new window
High grade PIN.
HISTOLOGY PROSTATE BIOPSY PROTOCOL
  • Effective immediately biopsies will be cut by histology in the following way:
  • Slide #1  ribbon for H&E
  • Slide #2  unstained slide containing two sections 
  • Slide #3  ribbon for H&E
  • Slide #4  unstained slide containing two sections
  • After examining slide #1 and #3, immunohistochemical stains can be performed on level #2 or #4 depending on which level you feel would better address the atypia you are concerned about.
  • Both high molecular weight keratin and AMACR can be performed on one slide using the double stain technique just illustrated. The other unstained slide will be used for the negative control.
HISTOLOGY PROSTATE BIOPSY PROTOCOL
  • Effective immediately biopsies will be cut by histology in the following way:
  • Slide #1ribbon for H&E
  • Slide #2unstained slide containing two sections
  • Slide #3ribbon for H&E
  • Slide #4unstained slide containing two sections
  • After examining slide #1 and #3, immunohistochemical stains can be performed on level #2 or #4 depending on which level you feel would better address the atypia you are concerned about.
  • Both high molecular weight keratin and AMACR can be performed on one slide using the double stain technique just illustrated. The other unstained slide will be used for the negative control.

As usual, this IHC is available to order via our web form:

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