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July 2003
Richard A. Savage, MD
Q. My
colleagues and I are seeking information about assessing micrometastases
and submicrometastases in sentinel lymph nodes examined for breast
cancer. The recent revisions to the American Joint Committee on
Cancer staging system define isolated tumor cells as deposits no
larger than 0.2 mm in diameter and micrometastases as deposits ranging
from 0.2 to 2.0 mm in diameter. When assessing single nodes with
multiple small deposits, should these be classified based on the
largest single metastatic focus or the aggregate dimension?
A.
The largest contiguous focus is used to determine the N category.
The AJCC Cancer Staging Manual1 defines
isolated tumor cells as cellular clusters no larger than 0.2 mm
in largest dimension [italics added]. Similarly, micrometastases
are larger than 0.2 mm but not larger than 2.0 mm in largest
dimension [italics added]. While not explicitly stated, there
is no provision in the AJCC system for combining the sizes of multiple
cellular clusters into a single aggregate dimension.
A sentinel lymph
node containing three clusters of tumor cells measuring 0.9 mm,
0.7 mm, and 0.6 mm would be reported as pN1mi (sn) (largest focus,
0.9 mm), while a node with three clusters each measuring 0.1 mm
would be reported as pN0 (sn) (largest focus, 0.1 mm). We recommend
including a comment in the report describing the number of separate
foci found.
On occasion,
these staging rules do not adequately describe the pathologic findings.
For instance, invasive lobular carcinoma may show extensive nodal
involvement by individually dispersed cells without forming discrete
cellular nests. Classifying such cases as isolated tumor cells might
be considered technically correct but would be an inaccurate characterization
of the pathologic findings. In such cases, you must select staging
categories that more accurately reflect the findings—that
is, pN1mi, pN1, or pN2—based on the number of nodes involved
and the extent of nodal involvement.
When faced with
a deviation from the usual staging rules, pathologists should include
a comment in their report describing why they chose a specific N
category.
Reference
1. Greene FL,
Page DL, Fleming ID, et al, eds. AJCC Cancer Staging Manual.
6th ed. New York, NY: Springer; 2002.
Patrick L. Fitzgibbons, MD
St. Jude Medical Center
Fullerton, Calif.
Advisor, CAP Surgical
Pathology Committee
Donald L. Weaver, MD
Fletcher Allen Health Care
University of Vermont
College of Medicine
Burlington, VT
Member, AJCC Breast Task Force
Q. Why
is there disparity among the experts regarding separating malignant
melanoma into Clark levels III and IV?
A.
Level III is a tumor that fills the papillary dermis without extending
into the reticular dermis. Level IV melanomas involve the reticular
dermis. Disparity among consultants exists for the following reasons:
- The reticular
dermis is not well delineated in normal skin.
- Tumor involving
the dermis may obliterate the landmarks delineating the beginning
of the reticular dermis, making it even more difficult to select
the proper level.
- Inflammation
may obscure the delineation between the end of the papillary dermis
and the beginning of the reticular dermis.
For these reasons,
Breslow measurements remain the best approach to depth related to
prognosis. Even Breslow measurements, however, have issues, including
the subjectivity of deciding whether a cell is part of a nevus,
melanoma cell, or inflammatory cell. If there is ulceration, one
can only estimate the location of the granular layer. If blocks
are step sectioned, the level may change by an average of 0.14 mm
in depth.
Paul Bozzo, MD
Medical Director
PBC Laboratory
Professor, Clinical Pathology
University of Arizona
Tucson
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