• Alpha methylacyl CoA racemase (AMACR) is a mitochondrial and peroxisomal enzyme, a 382 amino acid protein essential in lipid metabolism, encoded by a 1621 bp sequence gene, located on chromosome 5p13 (J Clin Pathol 2003;56:892)
• One of the most widely used markers of prostate carcinoma, because this protein is upregulated in prostate carcinoma and not found in benign prostate tissue (J Clin Pathol 2003;56:892, Am J Surg Pathol 2014;38:e6)

Contributed by Jonathan Epstein, M.D., Debra Zynger, M.D.

• Kidney:
  • Epithelial cells of the proximal tubules show strong and distinct granular cytoplasmic staining (The Human Protein Atlas: AMACR [Accessed 21 April 2020])
  • Epithelial cells of the distal tubules show a weak granular cytoplasmic staining reaction
• GI / liver:
  • Hepatocytes and epithelium of the gastrointestinal tract show moderate cytoplasmic staining

• Prostate:
  • Prostatic adenocarcinoma: majority are positive with sensitivity from 82% to 100% (Am J Surg Pathol 2014;38:e6, Am J Surg Pathol 2007;31:889, Am J Surg Pathol 2003;27:772)
  • High grade prostatic intraepithelial neoplasia (HGPIN) (J Urol 2006;175:820, Int J Clin Exp Pathol 2009;2:327)
  • Partial atrophy: can also lack basal cell expression (Am J Surg Pathol 2008;32:851)
  • Adenosis and other small glandular proliferations: on needle biopsy 64% of cases of crowded glands are positive and most had patchy or patchy / negative basal cells (Am J Surg Pathol 2005;29:874)
• Kidney:
  • Papillary renal cell carcinoma (Am J Surg Pathol 2014;38:e35)
  • MiTF-TFE translocation associated renal cell carcinoma (Am J Surg Pathol 2014;38:e35)
• Urothelial tract:
  • Urothelial carcinoma in situ (sensitivity 73% and specificity 97%) (Diagn Pathol 2019;14:91)
  • Nephrogenic adenoma: can also be negative for basal cell markers (Ann Diagn Pathol 2019;38:11, Hum Pathol 2019;94:11)
  • Clear cell adenocarcinoma
  • Skene gland adenocarcinoma (Am J Surg Pathol 2018;42:1513)
• Gynecologic:
  • Mesonephric carcinoma
  • Clear cell carcinoma (Appl Immunohistochem Mol Morphol 2019 Jul 29 [Epub ahead of print])
• GI / liver:
  • Barrett esophagus, ulcerative colitis, Crohn's disease: marker of dysplasia and carcinoma (Am J Surg Pathol 2006;30:871, J Clin Diagn Res 2017;11:EC35, Twitter: Andres Matoso [Accessed 21 April 2020])
  • Gastric adenocarcinoma
  • Colonic adenocarcinoma (J Clin Diagn Res 2016;10:EC10)
• Melanoma / dysplastic nevi: might distinguish from conventional melanocytic nevi (Tumour Biol 2014;35:12015)

• Kidney:
  • Clear cell renal cell carcinoma
  • Clear cell papillary renal cell carcinoma
  • Chromophobe renal cell carcinoma
  • Metanephric adenoma
  • Wilms tumor
• Prostate:
  • Nonneoplastic prostatic tissue (Int J Clin Exp Pathol 2009;2:327, Am J Surg Pathol 2014;38:e6, Am J Surg Pathol 2007;31:889, Am J Surg Pathol 2003;27:772)
• Urothelial tract:
  • Nonneoplastic urothelium
• Papillary cystadenoma of the epididymis and broad ligament: 20% may weakly express (Am J Surg Pathol 2014;38:713)

Biopsy of a lymph node shows metastasis of an unknown tumor. Which immunohistochemical panel is consistent with primary prostate carcinoma?

1. AE1 / AE3-, S100+, MelanA+, AMACR+
2. AMACR+, CDX2+, CK20+
3. AMACR+, p63-, HMWCK-, NKX3.1+
4. AMACR+, p63+, HMWCK+, NKX3.1-

C. AMACR+, p63-, HMWCK-, NKX3.1+

Comment Here

Reference: AMACR

Transurethral resection of the urinary bladder reveals a neoplastic proliferation, composed of small glandular structures, which are positive for AMACR and NKX3.1. What is the diagnosis?

1. Adenocarcinoma of the urinary bladder, intestinal type
2. Clear cell adenocarcinoma urinary bladder
3. Invasive urothelial carcinoma
4. Prostate adenocarcinoma (metastatic or direct invasion)

D. Prostate adenocarcinoma (metastatic or direct invasion)

Comment Here

Reference: AMACR

Biopsy of the paraaortal lymph node of a 60 year old man shows metastatic tumor (figure A), which is positive for 34 beta E12 (figure B) and AMACR (figure C) but negative for NKX3.1 (figure D). The tumor is also positive for GATA and CK7 (not shown) but negative for CDX2 (not shown). What is the diagnosis?

1. Metastatic colorectal adenocarcinoma
2. Metastatic prostate adenocarcinoma
3. Metastatic squamous cell carcinoma
4. Metastatic urothelial cell carcinoma

D. Metastatic urothelial cell carcinoma

Comment Here

Reference: AMACR

In the resection specimen of the urinary bladder of a 60 year old man with known invasive high grade urothelial cell carcinoma and multifocal carcinoma in situ, a glandular and cystic lesion was found under the urothelial lining (see image). The lesion is positive for PAX8 and AMACR. What is the diagnosis?

1. Invasive urothelial cell carcinoma
2. Metastatic colorectal adenocarcinoma
3. Metastatic prostate adenocarcinoma
4. Nephrogenic adenoma

D. Nephrogenic adenoma

Comment Here

Reference: AMACR