Optimization of the capture of Optimization of the capture of “difficult targets” “difficult targets”

in tissue microarraysin tissue microarrays

Chris MoskalukChris Moskaluk

University of VirginiaUniversity of Virginia

The “perfect” tissue target approximates a cylinder with The “perfect” tissue target approximates a cylinder with sides parallel to the direction of the TMA sampling needle, sides parallel to the direction of the TMA sampling needle, and that extends to the full thickness of the paraffin block.and that extends to the full thickness of the paraffin block.

Some target tissues are thin, requiring double sampling with the Some target tissues are thin, requiring double sampling with the TMA needles, with subsequent stacking of the tissue cores in TMA needles, with subsequent stacking of the tissue cores in the TMA block.the TMA block.

““Double stacked” TMA coresDouble stacked” TMA cores

Some target tissues veer off at acute angles from the surface of the Some target tissues veer off at acute angles from the surface of the donor paraffin block. The course of the target tissue cannot be donor paraffin block. The course of the target tissue cannot be predicted from examination of the guide H&E histologic section.predicted from examination of the guide H&E histologic section.

Target tissue is often a complex 3 dimensional structure within Target tissue is often a complex 3 dimensional structure within the donor paraffin block. Larger cores or multiple sampling may the donor paraffin block. Larger cores or multiple sampling may be required to effect capture of target tissue in serial sections of a be required to effect capture of target tissue in serial sections of a TMA block.TMA block.

Optimization studyOptimization study

Hypothesis: larger core sizes will capture Hypothesis: larger core sizes will capture more tissuemore tissue• Core sizes: 0.6, 1, 1.5, 2 mmCore sizes: 0.6, 1, 1.5, 2 mm• Area increases as a square of the radiusArea increases as a square of the radius

What number of what size cores are needed What number of what size cores are needed to capture “difficult” targets for at least 100 to capture “difficult” targets for at least 100 histologic sections? histologic sections?

TMA spot sizesTMA spot sizes

20 X original magnification20 X original magnification

Optimization studyOptimization study

Target tissuesTarget tissues• Brunner glands of duodenumBrunner glands of duodenum• Breast lobules and ductsBreast lobules and ducts• Bile ducts in liver portal tractsBile ducts in liver portal tracts• Pancreatic isletsPancreatic islets

5 different donor blocks per target tissue5 different donor blocks per target tissue 2 duplicate microarrays2 duplicate microarrays

• 0.6 mm cores: 10 x 2 = 200.6 mm cores: 10 x 2 = 20• 1 mm cores: 10 x 2 = 201 mm cores: 10 x 2 = 20• 1.5 mm cores: 4 x 2 = 81.5 mm cores: 4 x 2 = 8• 2 mm cores: 4 x 2 = 82 mm cores: 4 x 2 = 8

TMA block with 0.6, 1, 1.5 and 2 mm tissue coresTMA block with 0.6, 1, 1.5 and 2 mm tissue cores

125

5075

100125

0.6 mm

1 mm

1.5 mm

2 mm

0

10

20

30

40

50

60

70

80

90

100

Breast epithelium

0.6 mm

1 mm

1.5 mm

2 mm

Histologic level

% capture(per core)

Tissue spot diameter

Histologic level

% capture(per core)

Tissue spot diameter1

2550

75100

125

0.6 mm

1 mm

1.5 mm

2 mm

0

10

20

30

40

50

60

70

80

90

100

Brunner glands

0.6 mm

1 mm

1.5 mm

2 mm

Histologic level

% capture(per core)

Tissue spot diameter1

2550

75100

125

0.6 mm

1 mm

1.5 mm

2 mm

0

10

20

30

40

50

60

70

80

90

100

Liver bile ducts

0.6 mm

1 mm

1.5 mm

2 mm

125

5075

100125

0.6 mm

1 mm

1.5 mm

2 mm

0

10

20

30

40

50

60

70

80

90

100

Pancreatic islets

0.6 mm

1 mm

1.5 mm

2 mm

Histologic level

% capture(per core)

Tissue spot diameter

ConclusionsConclusions

The number and the size of TMA cores The number and the size of TMA cores needed to efficiently capture target needed to efficiently capture target tissue will depend on the specific tissue will depend on the specific tissue targettissue target

For the most difficult targets, at least For the most difficult targets, at least two “large cores” (1.5 or 2 mm) may two “large cores” (1.5 or 2 mm) may be requiredbe required