Breslow's depth
Encyclopedia
In medicine
, Breslow's depth is used as a prognostic factor
in melanoma
of the skin
. It is a description of how deeply tumor cells have invaded.
Breslow's depth.
Subsequent studies confirmed and refined the role of depth of invasion in the prognosis of malignant melanoma. Currently, Breslow's depth is included in the AJCC staging
guidelines for melanoma as a major prognostic factor.
techniques, such as a wedge or punch biopsy, are less accurate. Breslow's depth cannot be calculated from a shave biopsy that only contains a portion of the tumor because it leads to an underestimation of its thickness.
Breslow's depth is determined by using an ocular micrometer
at a right angle
to the skin to directly measure the depth to which tumor cells
have invaded the skin
. Breslow's depth is measured from the granular layer
of the epidermis down to the deepest point of invasion (sometimes involving detached nests of cells).
staging of malignant melanoma. A large study validated the importance of Breslow's depth as one of the three most important prognostic factors in melanoma (the others being T stage and ulceration). Breslow's depth also accurately predicted the risk for lymph node
metastasis
, with deeper tumors being more likely to involve the nodes.
The above studies showed that depth was a continuous variable correlating with prognosis. However, for staging purposes, the most recent AJCC guidelines use cutoffs of 1 mm, 2 mm, and 4 mm to divide patients into stages.
Survival figures from British Association of Dermatologist Guidelines 2002
Breslow thickness in the presence of ulceration also gives useful prognostic information.
Five anatomical levels are recognized, and higher levels have worsening prognostic implications. These levels are:
Medicine
Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....
, Breslow's depth is used as a prognostic factor
Prognosis
Prognosis is a medical term to describe the likely outcome of an illness.When applied to large statistical populations, prognostic estimates can be very accurate: for example the statement "45% of patients with severe septic shock will die within 28 days" can be made with some confidence, because...
in melanoma
Melanoma
Melanoma is a malignant tumor of melanocytes. Melanocytes are cells that produce the dark pigment, melanin, which is responsible for the color of skin. They predominantly occur in skin, but are also found in other parts of the body, including the bowel and the eye...
of the skin
Skin
-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...
. It is a description of how deeply tumor cells have invaded.
History
Depth of invasion was first reported as a prognostic factor in melanoma by the pathologist Alexander Breslow, M.D. at George Washington University in 1970. In recognition of his contribution, the depth of invasion of melanoma is referred to by the eponymEponym
An eponym is the name of a person or thing, whether real or fictitious, after which a particular place, tribe, era, discovery, or other item is named or thought to be named...
Breslow's depth.
Subsequent studies confirmed and refined the role of depth of invasion in the prognosis of malignant melanoma. Currently, Breslow's depth is included in the AJCC staging
Cancer staging
The stage of a cancer is a description of the extent the cancer has spread. The stage often takes into account the size of a tumor, how deeply it has penetrated, whether it has invaded adjacent organs, how many lymph nodes it has metastasized to , and whether it has spread to distant organs...
guidelines for melanoma as a major prognostic factor.
Measurement
Breslow's depth is most accurately measured by evaluating the entire tumor via an excisional biopsy. Determination from specimens obtained using other biopsyBiopsy
A biopsy is a medical test involving sampling of cells or tissues for examination. It is the medical removal of tissue from a living subject to determine the presence or extent of a disease. The tissue is generally examined under a microscope by a pathologist, and can also be analyzed chemically...
techniques, such as a wedge or punch biopsy, are less accurate. Breslow's depth cannot be calculated from a shave biopsy that only contains a portion of the tumor because it leads to an underestimation of its thickness.
Breslow's depth is determined by using an ocular micrometer
Ocular micrometer
An ocular micrometer is a glass disk that fits in a microscope eyepiece that has a ruled scale, which is used to measure the size of magnified objects. The physical length of the marks on the scale depend on the degree of magnification.-External links:*...
at a right angle
Right angle
In geometry and trigonometry, a right angle is an angle that bisects the angle formed by two halves of a straight line. More precisely, if a ray is placed so that its endpoint is on a line and the adjacent angles are equal, then they are right angles...
to the skin to directly measure the depth to which tumor cells
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...
have invaded the skin
Skin
-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...
. Breslow's depth is measured from the granular layer
Stratum granulosum
The stratum granulosum is a thin layer of cells in the epidermis. Keratinocytes migrating from the underlying stratum spinosum become known as granular cells in this layer...
of the epidermis down to the deepest point of invasion (sometimes involving detached nests of cells).
Prognostic importance
Breslow's depth is one of the cornerstones of the current AJCC TNMTNM
The TNM Classification of Malignant Tumours is a cancer staging system that describes the extent of cancer in a patient’s body.*T describes the size of the tumor and whether it has invaded nearby tissue,...
staging of malignant melanoma. A large study validated the importance of Breslow's depth as one of the three most important prognostic factors in melanoma (the others being T stage and ulceration). Breslow's depth also accurately predicted the risk for lymph node
Lymph node
A lymph node is a small ball or an oval-shaped organ of the immune system, distributed widely throughout the body including the armpit and stomach/gut and linked by lymphatic vessels. Lymph nodes are garrisons of B, T, and other immune cells. Lymph nodes are found all through the body, and act as...
metastasis
Metastasis
Metastasis, or metastatic disease , is the spread of a disease from one organ or part to another non-adjacent organ or part. It was previously thought that only malignant tumor cells and infections have the capacity to metastasize; however, this is being reconsidered due to new research...
, with deeper tumors being more likely to involve the nodes.
The above studies showed that depth was a continuous variable correlating with prognosis. However, for staging purposes, the most recent AJCC guidelines use cutoffs of 1 mm, 2 mm, and 4 mm to divide patients into stages.
| Breslow Thickness | Approximate 5 year survival |
|---|---|
| <1 mm | 95-100% |
| 1 - 2 mm | 80-96% |
| 2.1 - 4 mm | 60-75% |
| >4 mm | 50% |
Survival figures from British Association of Dermatologist Guidelines 2002
Breslow thickness in the presence of ulceration also gives useful prognostic information.
Clark's level
Clark's level is a related staging system, used in conjunction with Breslow's depth, which describes the level of anatomical invasion of the melanoma in the skin. Clark's level was the primary factor in earlier AJCC staging schemae for melanoma. However, with further study, it has been shown that Clark's level has a lower predictive value, is less reproducible, and is more operator-dependent as compared with Breslow's depth. Thus, in the current (2010) AJCC staging system, Clark's level has prognostic significance only in patients with very thin (Breslow depth <1 mm) melanomas.Five anatomical levels are recognized, and higher levels have worsening prognostic implications. These levels are:
- Melanoma confined to the epidermis (melanoma in situ)
- Invasion into the papillary dermis
- Invasion to the junction of the papillary and reticular dermisReticular dermisThe reticular dermis is the lower layer of the dermis, found under the papillary dermis, composed of dense irregular connective tissue featuring densely packed collagen fibers. It is the primary location of dermal elastic fibers....
- Invasion into the reticular dermisReticular dermisThe reticular dermis is the lower layer of the dermis, found under the papillary dermis, composed of dense irregular connective tissue featuring densely packed collagen fibers. It is the primary location of dermal elastic fibers....
- Invasion into the subcutaneous fat
External links
- Melanoma Staging Systems. National Cancer Institute. A resource on Clark's levels and Breslow's depth.
- Breslow Thickness and Ulceration Predict Survival. Malignant-Melanoma.org. Article demonstrating how Breslow Thickness relates to prognosis and survival time in melanoma.