Training Program SLN Micrometastasis vs ITC

Roderick R. Turner, MD

Adjunct Member, JWCI

Introduction

• ITC and micrometastasis are distinguished on the basis of the greatest dimension of the largest cluster of tumor cells.

• Each cluster or single cell is measured separately.• The number of clusters or single cells does not change

categorization; but, in clinical practice, an explanatory comment may be added to a report.

• Infrequently, small volume axillary disease may be seen only in perinodal soft tissue or afferent lymphatics; this is regarded as nodal metastasis and classified, as above, by cluster size.

Definitions - Cluster

• A cluster is a confluent focus of tumor cells touching other tumor cells. This is determined from the two-dimensional image of the microscopic section.

• Clusters or cells separated by a single benign cell or a spatial gap are measured as separate clusters, except when fibroblastic reaction to the tumor cells has caused the separation.

Definitions - Measurements

• Measurements are determined by the greatest dimension of the largest tumor cell cluster. Single cells are measured separately. A known field diameter (or ocular micrometer) should be utilized for consistent and reliable categorization.

• Measurements are made solely from the two-dimensional plane(s) of section(s) examined, H-E or IHC. In clinical practice, deeper sections and IHC are available options for further evaluation.

• Do not use the distance that separate clusters span, sum measurements of multiple clusters, or count/estimate tumor cell numbers.

Definitions – Isolated Tumor Cells

• Small cluster(s), largest cluster not greater than 0.20mm.• Single cells, as in the dispersed lobular pattern, represent ITC;

densely crowded cells when contiguous/touching are measured and classified by the largest group of contiguous/touching cells.

• A single cell may qualify as ITC, but only when cytologic and microanatomic features are supportive of a carcinoma cell. This may include a strongly positive immunoreaction. Cellular debris and contaminants are excluded.

• Mitotic activity (proliferation) is not considered.• Microanatomic location is not a factor in classification; ITC may be

found in nodal parenchyma, capsular or subcapsular spaces, or extranodal/afferent lymphatic vessels.

Definitions - Micrometastasis

• Largest cluster or confluent focus is greater than 0.20mm, but no greater than 2.0mm.

• Usually seen in nodal parenchyma; but,when found in perinodal tissue, it is classified as for nodal disease based on size of deposit.

• For borderline or indeterminate findings, at the two ends of this spectrum, select the lower N classification.

0.2 mm

TC #1 (1 of 2) Mostly ITC clusters, micrometastasis on right. See next.

0.2 mm

TC#1 (2 of 2) Small contiguous micrometastasis, 0.25mm

2.0 mm

TC#2 (1 of 2) Clusters are separated by fibroblastic reaction; this is a small macrometastasis, 3.0mm. See next for better detail.

0.2 mm

TC#2 (2 of 2) The clusters are separated by fibroblastic reaction; largest dimension seen on previous slide (macrometastasis) is appropriate

TC#3 Small micrometastasis, 0.35mm, and other ITC clusters

0.2 mm2.0 mm

TC#4 (1 of 2) Lobular carcinoma, mostly single ITC. Upper right shows dense crowding. See next.

0.2 mm

TC#4 (2 of 2) Contiguous grouping of touching tumor cells measures 0.22mm and qualifies as micrometastasis

0.2 mm

TC#5 Small micrometastasis, 0.22mm, and ITC clusters

0.2 mm

TC#6 (1 of 2). Few clusters of ITC in nodal parenchyma. See next.

0.2 mm

TC#6 (2 of 2). Multiple ITC clusters in nodal parenchyma, largest 0.20mm.

0.2 mm

TC#7. Multiple tiny clusters and a poorly cohesive, but contiguous, one at upper left. Small micrometastasis, 0.23mm.

, TC#8 (1 of 2) Tumor cell clusters in perinodal soft tissue/capsule with fibroblastic reaction. Micrometastasis 1.5mm. See next.

TC#8 (2 of 2). Closer view of fibrotic reaction between clusters.

0.2 mm

TC#9 (1 of 2) Tubular pattern. Multiple clusters of ITC.

0.1 mm

TC#9 (2 of 2). Largest ITC cluster 0.16mm

0.1 mm

TC#10. Single cell, strongly CK-IHC (+), 3x diameter of lymphocytes. Minimally qualifies as ITC

TC#11. ITC, 3 cells, in parenchyma.

TC#12. Many ITC clusters and single cells.

0.1 mm

TC#13. Several clusters of ITC, largest approx 0.09mm.

TC#14. Multiple clusters of ITC in subcapsular sinus.

END