P504S, a-methylacyl-CoA racemase, AMACR

504S is a 382 amino acid cytoplasmic protein which has been recently identified by microarray screening of prostatic carcinomas. It has been identified with a-methylacyl-CoA racemase (AMACR), an enzyme that catalyses the racemization of a-methylacyl branched carbolic coenzyme A thioesters¹⁷. It is located in mitochondria and peroxisomes. Within peroxisomes, it plays a role in the oxidation of branched-chain fatty acids. It is also responsible for the racemization of an intermediate in the synthesis of bile acids. AMACR deficiency in humans has been linked to adult-onset sensory motor neuropathy and to infantile-onset liver dysfunction. Intriguingly, in neoplasia AMACR is most often expressed in tumours associated with a high fat diet, such as colonic and prostatic carcinoma.

Immunohistochemical expression

A range of non-neoplastic tissues express AMACR¹⁴:

prostate: expression is only occasional and at a lower level than in malignant glands, with greater expression in young men¹⁴.
periurethral glands show a consistent moderate level of positivity¹⁴.
liver
salivary gland
renal tubular epithelium: there is granular cytoplasmic plus brush border staining restricted to the proximal convoluted tubule.
pancreas

There is over-expression in a range of carcinomas (studied using tissue micro-arrays⁷):

colorectum

20 of 24 cases⁷

breast invasive ductal carcinoma

23/ of 52 cases⁷

prostatic adenocarcinoma

5 of 6 cases⁷

cervical squamous cell carcinoma

0 of 6 cases⁷

By prostatic tissue. Since benign prostatic glands produce some AMACR, careful antibody titration is essential to maximize the diagnostic efficacy of AMACR¹⁸. There have been two major studies which used slightly different categories for grading the degree of staining.

Jiang et al¹:

strongly positive: defined as continuous dark staining of cytoplasm.

weakly positive: defined as single or groups of cells with discontinuous or weak staining

negative

>75% of cells

51-75% of cells

6-50% of cells

<5% of cells

total

benign prostate (biopsy)

0/54¹

9/54¹

45/54¹

benign prostatic hyperplasia

0/13¹,0/20⁶

2/13¹

11/13¹,20/20⁶

benign, near carcinoma, biopsy

0/54¹

8/54¹

46/54¹

benign, near carcinoma, prostatectomy

0/73¹

4/73¹

69/73¹

benign, total

0/194¹

23/194¹

171/194¹

M
a
l
i
g
n
a
n
t

Gleason grade 2

10/10⁶

Gleason grade 3

10/10⁶

Gleason 5

2/2¹

0/2¹

0/2¹

0/2¹

2/2¹

0/2¹

0/2¹

Gleason 6

77/80¹

2/80¹

1/80¹

0/80¹

80/80¹

0/80¹

0/80¹

Gleason 7

28/32¹

1/32¹

1/32¹

2/32¹

32/32¹

0/32¹

0/32¹

Gleason >=8

19/23¹

323¹

023¹

123¹

23/23¹

0/23¹

0/23¹

Total

126

6

2

3

137/137¹

0/137¹

0/137¹

The small benign glands seen in atrophy, basal cell hyperplasia, inflamed glands, urothelial metaplasia and most adenoses were negative¹.

Beach et al found less clear-cut results, with some benign glands showing staining and some carcinomas which failed to stain²:

positive

negative

>51% of cells

11-50% of cells

1-10% of cells

total

benign

benign prostate, NOS

14/270 (almost always weak, luminal, and non-circumferential)²

64/270 (non-circumferential luminal staining)²

78/270²

192/270²

benign prostatic small gland proliferations

0/28 (post-atrophic hyperplasia:0/10, transitional metaplasia: 0/17, basal cell hyperplasia: 0/1)²

28/28²

benign prostate, atrophic

3/79 (focal, faint and non-circumferential)²

3/79²

76/79²

benign, total

14²

67²

81²

296²

Atypical adenomatous hyperplasia

7/40 (In four of seven AAH cases, P504S staining patterns were scattered (1-24% positive cells/gland), clustered, or focal (25-50% positive cells/gland), which were different from the typical P504S staining pattern in prostatic adenocarcinoma. Only in three of seven cases of AAH was the P504S reactivity diffuse (>95% positive cells/gland) and similar to that of prostatic adenocarcinoma. In two of three AAH cases with diffuse P504S staining, low-grade prostatic adenocarcinoma was observed within or adjacent to the focus of AAH.)⁶

33/40⁶

malignant

needle biopsies

60/186²

75/186²

18/186²

153/186²

33/186²

treated carcinoma

12/13 (hormonally-treated carcinoma: 8/8, radiation-treated carcinoma: 4/5.)²

1/13²

unusual morphological patterns in prostatectomies

14/16 (pseudohyperplastic pattern: 5/6, atrophic pattern: 2/2, ductal adenocarcinoma: 5/5, mucinous carcinoma: 2/3)²

2/16²

The prostatic stroma shows weak diffuse staining, which does not impede the interpretation of the staining of the epithelium². Invasive urothelial carcinoma is immunoreactive (6/6²). Seminal vesicles are negative (0/10²).

Both studies agree that the staining of prostatic carcinoma is irrespective of Gleason grade^1,2.

The question of the utility of P504S in core biopsies with small samples of carcinoma has been specifically addressed.

positive

negative

>75%

51-75%

25-50%

<25%

total

benign glands

142/142 (69 benign core biopsies and the benign glands in 73 cores with malignant glands)⁵

percentages of malignant glands immunoreactive

177/209³ , 63/73⁵

1/209³, 3/73⁵

4/209³, 3/73⁵

2/209³

184/209³ (88%), 69/73⁵

25/209³, 4/73 (Three Gleason grade 6, including one foamy cell cancer, and one of two Gleason grade 8)⁵

³Malignant glands were considered positive if the degree of staining was greater than that of the benign glands. Sensitivity in malignant glands varied from 80% to 100%, depending on the source institution for the biopsies. 3 of the 4 cases of Gleason grade 7 were negative for P504S, as were both of the prostatic carcinomas with ductal features. 31 of the 46 cases of high-grade PIN were positive. In 17 of the 209 cases, benign glands adjacent to the malignant glands showed focal apical border staining.

One study considered 793 prostatic needle cores that had been considered negative for carcinoma on initial H/E sections: 84 of these proved positive for P504S: nine of these cases were recognised as showing carcinoma, ten as showing atypia and fifty four as showing high-grade intra-epithelial neoplasia on review, while eleven cases were considered to be benign despite the positivity for P504S¹⁶.

Variants of prostatic carcinoma, including foamy gland cancer, pseudohyperplastic adenocarcinoma and atrophic adenocarcinoma show a lower sensitivity at 62-77%⁴^,9.

The monoclonal antibody P504S has been compared with polyclonal anti-AMACR. P504S has a slightly lower sensitivity but higher specificity for carcinoma compared with AMACR:

weakly positive

moderately or strongly positive

prostatic adenocarcinoma using tissue microarrays

P504S

21/69¹⁵

43/69¹⁵

p-AMACR

7/76¹⁵

69/76¹⁵

needle biopsies

unequivocal minute carcinoma (the 34bE12+p63 cocktail supported carcinoma in all cases)

P504S

5/20¹⁵

11/20 (one positive case was negative with p-AMACR)¹⁵

p-AMACR

3/20¹⁵

13/20 (one positive case was negative with P504S)¹⁵

"atypical" converted to carcinoma on basal marker

P504S

4/17¹⁵

8/17¹⁵

p-AMACR

2/17¹⁵

11/17¹⁵

"atypical" converted to carcinoma on AMACR (in all five cases, the diagnosis was confirmed after radical prostatectomy)

P504S

1/5¹⁵

4/5¹⁵

p-AMACR

2/5¹⁵

3/5¹⁵

"atypical" considered benign on the bases of positivity for basal markers

P504S

0/4

p-AMACR

0/4

combined sensitivity for TMA and needle biopsies

P504S

87%

p-AMACR

90%

weakly positive

moderately or strongly positive

high-grade PIN using tissue microarrays

P504S

13/43¹⁵

20/43¹⁵

p-AMACR

12/54¹⁵

40/54¹⁵

benign prostatic glands

P504S

8/120 (the cases that stained were focal and did not cause diagnostic difficulty)

0/120

p-AMACR

25/134 (the cases that stained were focal and did not cause diagnostic difficulty)

0/134

Nephrogenic adenoma may be positive for P504S, especially when the lesion occurs in the urethra.

P504S is commonly expressed in adenocarcinomas of the colorectum but not those of the small intestine:

Small intestinal carcinoma

Large intestinal carcinoma

P504S

Ampullary

other

primary colorectal

secondary colorectal

2/34 (Both positive cases were of intestinal type.)¹³

1/25 (The positive case was a poorly differentiated tumour of the jejunum.)¹³

29/42¹³

12/24¹³

mucinous

non-mucinous

1/12¹³

40/54¹³

well or moderately differentiated

poorly differentiated

40/60¹³

1/6¹³

MSI

MSS

5/14¹³

35/49¹³

CK7+/CK20+

17/34¹³

17/25¹³

4/66¹³

CK7+/CK20-

15/34¹³

8/25¹³

0/66¹³

CK7-/CK20+

2/34¹³

0/25¹³

58/66¹³

CK7-/CK20-

0/34¹³

0/25¹³

4/66¹³

Normal colorectal mucosa is negative for P504S¹³.

There is increasing expression of AMACR with increasing degrees of dysplasia in both Barrett's oesophagus and inflammatory bowel disease¹⁷:

Barrett's oesophagus

no dysplasia

0/36

indefinite for dysplasia

3/14 (1% to 10% of cells positive: 1 case, 10% to 50% of cells positive: 2 cases.)

low-grade dysplasia

6/16 (1% to 10% of cells positive: 2 cases, 10% to 50% of cells positive: 3 cases, more than 50% of cells positive: 1 case.)

high-grade dysplasia

26/32 (1% to 10% of cells positive: 9 cases, 10% to 50% of cells positive: 8 cases, more than 50% of cells positive: 9 cases.)

adenocarcinoma

26/36 (1% to 10% of cells positive: 5 cases, 10% to 50% of cells positive: 8 cases, more than 50% of cells positive: 13 cases.)

Inflammatory bowel disease

no dysplasia

0/17

indefinite for dysplasia

1/7 (1% to 10% of cells positive: this patient was found to have an adenocarcinoma of the oesophagus two months later.)

low-grade dysplasia

25/26 (1% to 10% of cells positive: 2 cases, 10% to 50% of cells positive: 8 cases, more than 50% of cells positive: 15 cases.)

high-grade dysplasia

8/10 (1% to 10% of cells positive: 1 case, 10% to 50% of cells positive: 2 cases, more than 50% of cells positive: 5 cases.)

adenocarcinoma

10/14 (10% to 50% of cells positive: 3 cases, more than 50% of cells positive: 7 cases.)

Diagnostic utility

Diagnosis of prostatic carcinoma, particularly on needle biopsy and the identification of minimal residual carcinoma, in conjunction with 34bE12, p63 and CK5/6, all of which stain basal cells in benign glands but not carcinoma. Positivity for AMACR appears to provide additional information to that of negativity for basal cell markers¹⁸. There appear to be significant variations in the sensitivity and specificity of P504S between institutions, depending on fixation and immunohistochemical methodology, in particular protease digestion, heat recovery and developer system⁸.

Positivity both for P504S and for either 34bE12 or p63 helps to identify high-grade prostatic intraepithelial neoplasia¹ and atypical adenomatous hyperplasia⁶.

Since p63 is a nuclear stain and P504S is a cytoplasmic stain, they can be applied as a cocktail to the same section. The use of a cocktail is advantageous for minute lesions which may cut out⁸:

p63

P504S

benign

+

-

atypical small acinar proliferation

-

-

high-grade prostatic intra-epithelial neoplasia

+

+

prostatic carcinoma

-

+

The sensitivity and specificity of both P504S and p63 have been shown to be as good in a cocktail as when used alone⁹:

positivity for P504S defined as granular cytoplasmic staining of the entire circumference of the gland.

P504S, when used alone

P504S, in cocktail with p63

High grade PIN

prostatectomy

25/27

24/27 (one case that showed focal weak staining with P504S in isolation failed to stain with the cocktail.)

needle biopsy

45/47

45/47

Minimal prostatic carcinoma

prostatectomy

18/18

18/18

needle biopsy

23/25

23/25

Prostatic carcinoma

prostatectomy

29/30 (positive cases included prostatic carcinoma with pseudohyperplastic features (1 case).)

28/30 (one case that showed focal weak staining with P504S in isolation failed to stain with the cocktail.)

needle biopsy

107/116 (positive cases included prostatic carcinoma with atrophic features (2 cases), signet-ring cell features (2 cases) and pseudohyperplastic features (1 case).)

107/116

The pattern of p63 staining was the same using the cocktail as using p63 in isolation.

The P504S/p63 cocktail proved useful in identifying and differentiating foci of minimal prostatic carcinoma (P504S+/p63-), HGPIN (P504S+/p63+), atrophic glands (a few cases showed focal P504S+ but were p63+) and basal cell hyperplasia(P504S-/p63+)⁹. In order to avoid spurious cytoplasmic staining by p63, it should be used at a sufficient dilution (1 in 500 for the human recombinant clone from Neomarkers)⁹.

Based on several papers:

sensitivity for carcinoma

sensitivity for high grade PIN

specificity for carcinoma

specificity for high grade PIN

P504S+/p63- in combination

97.2%¹⁰, 97.6%⁸

86.2%¹⁰

99.7%¹⁰, 95.2% (specificity may have been reduced by the inclusion of cases of atypical small acinar proliferation.)⁸

81.6%¹⁰

34bE12 negativity in isolation

67% to 94%^11,12

p63 negativity in isolation

91% to 98%^11,12

negativity for a 34bE12/p63 cocktail

98% (Basal cell cocktail not only increases the sensitivity of the basal cell detection, but also reduces the staining variability and therefore renders the basal cell immunostaining more consistent.)¹²

If AMACR is used in a cocktail with 34bE12 (with or without p63), both being cytoplasmic antigens, two chromogens need to be used.

As a member of a panel to differentiated primary ovarian endometrioid/mucinous carcinoma of the ovary from metastatic colorectal carcinoma.

Along with the cytokeratin profile (small intestine CK7+/CK20 variable, large intestine CK7-/CK20+), to differentiated between adenocarcinomas of the small intestine (negative for P504S) and the colorectum (positive for P504S).

The detection of dysplasia in Barrett's oesophagus and in inflammatory bowel disease.

References

¹Jiang, Z., Woda, B. A., Rock, K. L. P504S: a new molecular marker for the detection of prostate carcinoma. Am J Surg Pathol 2001;25:1397-1404.

²Beach, R., Gown, A.M., De Peralta-Venturina, M.N., Folpe, A.L., Yaziji, H., Salles, P.G., Grignon, D.J., Fanger, G.R. and Amin, M.B. P504S immunohistochemical detection in 405 prostatic specimens including 376 18-gauge needle biopsies. Am J Surg Pathol 2002;26:1588-96.

³Magi-Galluzzi, C., J. Luo, et al. (2003). "Alpha-methylacyl-CoA racemase: a variably sensitive immunohistochemical marker for the diagnosis of small prostate cancer foci on needle biopsy." Am J Surg Pathol 27(8): 1128-33.

⁴Zhou, M., Z. Jiang, et al. (2003). "Expression and diagnostic utility of alpha-methylacyl-CoA-racemase (P504S) in foamy gland and pseudohyperplastic prostate cancer." Am J Surg Pathol 27(6): 772-8.

⁵Jiang, Z., C. L. Wu, et al. (2002). "P504S/alpha-methylacyl-CoA racemase: a useful marker for diagnosis of small foci of prostatic carcinoma on needle biopsy." Am J Surg Pathol 26(9): 1169-74.

⁶Yang, X. J., C. L. Wu, et al. (2002). "Expression of alpha-Methylacyl-CoA racemase (P504S) in atypical adenomatous hyperplasia of the prostate." Am J Surg Pathol 26(7): 921-5.

⁷Zhou, M., A. M. Chinnaiyan, et al. (2002). "Alpha-Methylacyl-CoA racemase: a novel tumor marker over-expressed in several human cancers and their precursor lesions." Am J Surg Pathol 26(7): 926-31.

⁸Molinie, V., G. Fromont, et al. (2004). "Diagnostic utility of a p63/alpha-methyl-CoA-racemase (p504s) cocktail in atypical foci in the prostate." Mod Pathol 17(10): 1180-90.

⁹ Hameed O, Sublett J,Humphrey PA Immunohistochemical stains for p63 and alpha-methylacyl-CoA racemase, versus a cocktail comprising both, in the diagnosis of prostatic carcinoma: a comparison of the immunohistochemical staining of 430 foci in radical prostatectomy and needle biopsy tissues. Am J Surg Pathol 2005; 29:579-87

¹⁰ Sanderson SO, Sebo TJ, Murphy LM, et al. An analysis of the p63/alpha-methylacyl coenzyme A racemase immunohistochemical cocktail stain in prostate needle biopsy specimens and tissue microarrays. Am J Clin Pathol 2004; 121:220-5

¹¹ Shah RB, Zhou M, LeBlanc M, et al. Comparison of the basal cell-specific markers, 34betaE12 and p63, in the diagnosis of prostate cancer. Am J Surg Pathol 2002; 26:1161-8

¹² Zhou M, Shah R, Shen R, et al. Basal Cell Cocktail (34betaE12 + p63) Improves the Detection of Prostate Basal Cells. Am J Surg Pathol 2003; 27:365-71.

¹³Chen ZM, Ritter JH,Wang HL Differential expression of alpha-methylacyl coenzyme A racemase in adenocarcinomas of the small and large intestines. Am J Surg Pathol 2005; 29:890-6

¹⁴Gologan A, Bastacky S, McHale T, et al. Age-associated changes in alpha-methyl CoA racemase (AMACR) expression in nonneoplastic prostatic tissues. Am J Surg Pathol 2005; 29:1435-41

¹⁵Kunju LP, Chinnaiyan AM,Shah RB. Comparison of monoclonal antibody (P504S) and polyclonal antibody to alpha methylacyl-CoA racemase (AMACR) in the work-up of prostate cancer. Histopathology 2005; 47:587-96

¹⁶Carswell BM, Woda BA, Wang X, et al. Detection of prostate cancer by alpha-methylacyl CoA racemase (P504S) in needle biopsy specimens previously reported as negative for malignancy. Histopathology 2006; 48:668-73

¹⁷Dorer R,Odze RD. AMACR immunostaining is useful in detecting dysplastic epithelium in Barrett's esophagus, ulcerative colitis, and Crohn's disease. Am J Surg Pathol 2006; 30:871-7

¹⁸ Hammed O, Humphrey PA. Immunohistochemistry in the diagnosis of minimal prostate cancer. Current Diagnostic Pathology 2006;12:279-291.

This page last revised 22.9.2006.

colorectum	20 of 24 cases⁷
breast invasive ductal carcinoma	23/ of 52 cases⁷
prostatic adenocarcinoma	5 of 6 cases⁷
cervical squamous cell carcinoma	0 of 6 cases⁷

		strongly positive: defined as continuous dark staining of cytoplasm.					weakly positive: defined as single or groups of cells with discontinuous or weak staining	negative
		>75% of cells	51-75% of cells	6-50% of cells	<5% of cells	total		negative
benign prostate (biopsy)						0/54¹	9/54¹	45/54¹
benign prostatic hyperplasia						0/13¹,0/20⁶	2/13¹	11/13¹,20/20⁶
benign, near carcinoma, biopsy						0/54¹	8/54¹	46/54¹
benign, near carcinoma, prostatectomy						0/73¹	4/73¹	69/73¹
benign, total						0/194¹	23/194¹	171/194¹
M a l i g n a n t	Gleason grade 2	10/10⁶
	Gleason grade 3	10/10⁶
	Gleason 5	2/2¹	0/2¹	0/2¹	0/2¹	2/2¹	0/2¹	0/2¹
	Gleason 6	77/80¹	2/80¹	1/80¹	0/80¹	80/80¹	0/80¹	0/80¹
	Gleason 7	28/32¹	1/32¹	1/32¹	2/32¹	32/32¹	0/32¹	0/32¹
	Gleason >=8	19/23¹	323¹	023¹	123¹	23/23¹	0/23¹	0/23¹
	Total	126	6	2	3	137/137¹	0/137¹	0/137¹

		positive				negative
		>51% of cells	11-50% of cells	1-10% of cells	total	negative
benign	benign prostate, NOS	14/270 (almost always weak, luminal, and non-circumferential)²		64/270 (non-circumferential luminal staining)²	78/270²	192/270²
	benign prostatic small gland proliferations				0/28 (post-atrophic hyperplasia:0/10, transitional metaplasia: 0/17, basal cell hyperplasia: 0/1)²	28/28²
	benign prostate, atrophic			3/79 (focal, faint and non-circumferential)²	3/79²	76/79²
	benign, total	14²		67²	81²	296²
Atypical adenomatous hyperplasia					7/40 (In four of seven AAH cases, P504S staining patterns were scattered (1-24% positive cells/gland), clustered, or focal (25-50% positive cells/gland), which were different from the typical P504S staining pattern in prostatic adenocarcinoma. Only in three of seven cases of AAH was the P504S reactivity diffuse (>95% positive cells/gland) and similar to that of prostatic adenocarcinoma. In two of three AAH cases with diffuse P504S staining, low-grade prostatic adenocarcinoma was observed within or adjacent to the focus of AAH.)⁶	33/40⁶
malignant	needle biopsies	60/186²	75/186²	18/186²	153/186²	33/186²
	treated carcinoma				12/13 (hormonally-treated carcinoma: 8/8, radiation-treated carcinoma: 4/5.)²	1/13²
	unusual morphological patterns in prostatectomies				14/16 (pseudohyperplastic pattern: 5/6, atrophic pattern: 2/2, ductal adenocarcinoma: 5/5, mucinous carcinoma: 2/3)²	2/16²

	positive					negative
	>75%	51-75%	25-50%	<25%	total	negative
benign glands						142/142 (69 benign core biopsies and the benign glands in 73 cores with malignant glands)⁵
percentages of malignant glands immunoreactive	177/209³ , 63/73⁵	1/209³, 3/73⁵	4/209³, 3/73⁵	2/209³	184/209³ (88%), 69/73⁵	25/209³, 4/73 (Three Gleason grade 6, including one foamy cell cancer, and one of two Gleason grade 8)⁵

			weakly positive	moderately or strongly positive
prostatic adenocarcinoma using tissue microarrays		P504S	21/69¹⁵	43/69¹⁵
		p-AMACR	7/76¹⁵	69/76¹⁵

needle biopsies	unequivocal minute carcinoma (the 34bE12+p63 cocktail supported carcinoma in all cases)	P504S	5/20¹⁵	11/20 (one positive case was negative with p-AMACR)¹⁵
		p-AMACR	3/20¹⁵	13/20 (one positive case was negative with P504S)¹⁵
	"atypical" converted to carcinoma on basal marker	P504S	4/17¹⁵	8/17¹⁵
	"atypical" converted to carcinoma on basal marker	p-AMACR	2/17¹⁵	11/17¹⁵
	"atypical" converted to carcinoma on AMACR (in all five cases, the diagnosis was confirmed after radical prostatectomy)	P504S	1/5¹⁵	4/5¹⁵
		p-AMACR	2/5¹⁵	3/5¹⁵
	"atypical" considered benign on the bases of positivity for basal markers	P504S	0/4
		p-AMACR	0/4
combined sensitivity for TMA and needle biopsies		P504S	87%
combined sensitivity for TMA and needle biopsies		p-AMACR	90%
			weakly positive	moderately or strongly positive
high-grade PIN using tissue microarrays		P504S	13/43¹⁵	20/43¹⁵
high-grade PIN using tissue microarrays		p-AMACR	12/54¹⁵	40/54¹⁵
benign prostatic glands		P504S	8/120 (the cases that stained were focal and did not cause diagnostic difficulty)	0/120
benign prostatic glands		p-AMACR	25/134 (the cases that stained were focal and did not cause diagnostic difficulty)	0/134

	Small intestinal carcinoma		Large intestinal carcinoma
P504S	Ampullary	other	primary colorectal	secondary colorectal
	2/34 (Both positive cases were of intestinal type.)¹³	1/25 (The positive case was a poorly differentiated tumour of the jejunum.)¹³	29/42¹³	12/24¹³

			mucinous	non-mucinous
			1/12¹³	40/54¹³

			well or moderately differentiated	poorly differentiated
			40/60¹³	1/6¹³

			MSI	MSS
			5/14¹³	35/49¹³
CK7+/CK20+	17/34¹³	17/25¹³	4/66¹³
CK7+/CK20-	15/34¹³	8/25¹³	0/66¹³
CK7-/CK20+	2/34¹³	0/25¹³	58/66¹³
CK7-/CK20-	0/34¹³	0/25¹³	4/66¹³

Barrett's oesophagus	no dysplasia	0/36
	indefinite for dysplasia	3/14 (1% to 10% of cells positive: 1 case, 10% to 50% of cells positive: 2 cases.)
	low-grade dysplasia	6/16 (1% to 10% of cells positive: 2 cases, 10% to 50% of cells positive: 3 cases, more than 50% of cells positive: 1 case.)
	high-grade dysplasia	26/32 (1% to 10% of cells positive: 9 cases, 10% to 50% of cells positive: 8 cases, more than 50% of cells positive: 9 cases.)
	adenocarcinoma	26/36 (1% to 10% of cells positive: 5 cases, 10% to 50% of cells positive: 8 cases, more than 50% of cells positive: 13 cases.)
Inflammatory bowel disease	no dysplasia	0/17
	indefinite for dysplasia	1/7 (1% to 10% of cells positive: this patient was found to have an adenocarcinoma of the oesophagus two months later.)
	low-grade dysplasia	25/26 (1% to 10% of cells positive: 2 cases, 10% to 50% of cells positive: 8 cases, more than 50% of cells positive: 15 cases.)
	high-grade dysplasia	8/10 (1% to 10% of cells positive: 1 case, 10% to 50% of cells positive: 2 cases, more than 50% of cells positive: 5 cases.)
	adenocarcinoma	10/14 (10% to 50% of cells positive: 3 cases, more than 50% of cells positive: 7 cases.)

	p63	P504S
benign	+	-
atypical small acinar proliferation	-	-
high-grade prostatic intra-epithelial neoplasia	+	+
prostatic carcinoma	-	+

positivity for P504S defined as granular cytoplasmic staining of the entire circumference of the gland.		P504S, when used alone	P504S, in cocktail with p63
High grade PIN	prostatectomy	25/27	24/27 (one case that showed focal weak staining with P504S in isolation failed to stain with the cocktail.)
High grade PIN	needle biopsy	45/47	45/47
Minimal prostatic carcinoma	prostatectomy	18/18	18/18
Minimal prostatic carcinoma	needle biopsy	23/25	23/25
Prostatic carcinoma	prostatectomy	29/30 (positive cases included prostatic carcinoma with pseudohyperplastic features (1 case).)	28/30 (one case that showed focal weak staining with P504S in isolation failed to stain with the cocktail.)
Prostatic carcinoma	needle biopsy	107/116 (positive cases included prostatic carcinoma with atrophic features (2 cases), signet-ring cell features (2 cases) and pseudohyperplastic features (1 case).)	107/116
The pattern of p63 staining was the same using the cocktail as using p63 in isolation.

	sensitivity for carcinoma	sensitivity for high grade PIN	specificity for carcinoma	specificity for high grade PIN
P504S+/p63- in combination	97.2%¹⁰, 97.6%⁸	86.2%¹⁰	99.7%¹⁰, 95.2% (specificity may have been reduced by the inclusion of cases of atypical small acinar proliferation.)⁸	81.6%¹⁰
34bE12 negativity in isolation			67% to 94%^11,12
p63 negativity in isolation			91% to 98%^11,12
negativity for a 34bE12/p63 cocktail			98% (Basal cell cocktail not only increases the sensitivity of the basal cell detection, but also reduces the staining variability and therefore renders the basal cell immunostaining more consistent.)¹²

P504S, a-methylacyl-CoA racemase, AMACR

Immunohistochemical expression

There is over-expression in a range of carcinomas (studied using tissue micro-arrays7):

By prostatic tissue. Since benign prostatic glands produce some AMACR, careful antibody titration is essential to maximize the diagnostic efficacy of AMACR18. There have been two major studies which used slightly different categories for grading the degree of staining.

The small benign glands seen in atrophy, basal cell hyperplasia, inflamed glands, urothelial metaplasia and most adenoses were negative1.

Variants of prostatic carcinoma, including foamy gland cancer, pseudohyperplastic adenocarcinoma and atrophic adenocarcinoma show a lower sensitivity at 62-77%4,9.