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The End of the Clark Level

By February 15, 2009

Melanoma staging can be confusing for patients -- it's full of technical jargon and obscure definitions. For example, many patients hear that their melanoma has a Clark level of four and they panic, thinking that's the same thing as stage IV. (Just to be clear: the former refers to how deep the tumor has penetrated into the skin, while the latter refers to an advanced stage of metastatic melanoma that has a poor prognosis.)

Doctors are planning to introduce a new version (the seventh!) of the melanoma staging system in 2010 with the Clark level eliminated. This continues an ongoing trend: in recent years, Clark's levels have been used less and less for calculating prognosis, since research has shown them to be less predictive of outcome, less reproducible, and more subjective than the Breslow thickness (the total height of the tumor). The definition of stage I, II and III melanoma will mostly stay the same, but the mitotic rate (a measure of the number of dividing cancerous cells) will be introduced into the staging system on the basis of recent evidence that it's an independent predictor of survival.

So, starting next year, pathology reports for melanoma will include the Breslow thickness, mitotic rate, presence or absence of ulceration (which occurs when melanoma breaks through the skin), and margin status (the presence of cancer in the skin surrounding the tumor).


"New AJCC Melanoma Staging System Described." Elsevier Global Medical News. 9 Feb 2009.

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