medicine Medicine is the science and Praxis (process), practice of caring for patients, managing the Medical diagnosis, diagnosis, prognosis, Preventive medicine, prevention, therapy, treatment, Palliative care, palliation of their injury or disease, ...

, Breslow's depth was used as a prognostic factor in

melanoma Melanoma is the most dangerous type of skin cancer; it develops from the melanin-producing cells known as melanocytes. It typically occurs in the skin, but may rarely occur in the mouth, intestines, or eye (uveal melanoma). In very rare case ...

of the

skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other animal coverings, such as the arthropod exoskeleton, have different ...

. It is a description of how deeply tumor cells have invaded. Currently, the standard Breslow's depth has been replaced by the AJCC depth, in the AJCC staging system of melanoma. Originally, Breslow's depth was divided into 5 stages.

Classification

History

Depth of invasion was first reported as a prognostic factor in melanoma by the

pathologist Pathology is the study of disease. The word ''pathology'' also refers to the study of disease in general, incorporating a wide range of biology research fields and medical practices. However, when used in the context of modern medical treatme ...

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

eponym An eponym is a noun after which or for which someone or something is, or is believed to be, named. Adjectives derived from the word ''eponym'' include ''eponymous'' and ''eponymic''. Eponyms are commonly used for time periods, places, innovati ...

''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.

Measurement

Tumor depth is most accurately measured by evaluating the entire tumor via an excisional biopsy. Determination from specimens obtained using other

biopsy A biopsy is a medical test commonly performed by a surgeon, interventional radiologist, an interventional radiologist, or an interventional cardiology, interventional cardiologist. The process involves the extraction of sampling (medicine), sample ...

techniques, such as a wedge or punch biopsy, are less accurate. Tumor 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 In geometry and trigonometry, a right angle is an angle of exactly 90 Degree (angle), degrees or radians corresponding to a quarter turn (geometry), turn. If a Line (mathematics)#Ray, ray is placed so that its endpoint is on a line and the ad ...

to the skin to directly measure the depth to which

tumor cells A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...

have invaded the

. Breslow's depth is measured from the granular layer of the

epidermis The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and Subcutaneous tissue, hypodermis. The epidermal layer provides a barrier to infection from environmental pathogens and regulates the ...

down to the deepest point of invasion (sometimes involving detached nests of cells).

Prognostic importance

Tumor depth is one of the cornerstones of the current AJCC

TNM staging The TNM Classification of Malignant Tumors (TNM) is a globally recognised standard for classifying the anatomical extent of the spread of malignant tumours (cancer). It has gained wide international acceptance for many solid tumor cancers, but is ...

of malignant melanoma. A large study validated the importance of tumor depth (but not Breslow's original description) 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 A lymph node, or lymph gland, is a kidney-shaped organ of the lymphatic system and the adaptive immune system. A large number of lymph nodes are linked throughout the body by the lymphatic vessels. They are major sites of lymphocytes that includ ...

metastasis Metastasis is a pathogenic agent's spreading from an initial or primary site to a different or secondary site within the host's body; the term is typically used when referring to metastasis by a cancerous tumor. The newly pathological sites, ...

, 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

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.Weedon, D. Skin pathology. 2nd Edition. 2002. Sydney: Churchill-Livingstone. Clark's level was the primary factor in earlier AJCC staging schemas 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: *Level 1: Melanoma confined to the

(melanoma in situ) *Level 2: Invasion into the papillary dermis *Level 3: Invasion to the junction of the papillary and reticular dermis *Level 4: Invasion into the reticular dermis *Level 5: Invasion into the subcutaneous fat

References

{{Reflist

External links

Melanoma Staging Systems
National Cancer Institute. A resource on Clark's levels and Breslow's depth. Cancer staging Dermatologic terminology Histopathology Melanocytic nevi and neoplasms