Is this correct?

[bon15]

I have come across this extract several times on the internet:

Based on this analysis, primary melanoma mitotic rate was incorpo­rated into the 7th edition of the AJCC Cancer Staging Manual as a required element for melanoma staging. These recommendations were made after reviewing the statistical informa­tion involving 4,861 T1 melanomas from the updated AJCC Melanoma Staging Database demonstrating that mitotic rate was the most powerful predictor of survival outcome for T1 melanoma patients, and conversely, that the Clark’s level of invasion was no longer statistically significant when mitotic rate and ulceration were in­cluded.1 Ten-year survival rates were 97 percent for T1 melanomas 0.1-0.50 mm in thickness and <1 mitosis/mm2, 95 percent for T1 melanomas 0.1-0.50 mm in thickness and ≥1 mitosis/mm2, 93 percent for T1 melanomas 0.51-1.0 mm and <1 mitosis/mm2, and 87 per­cent for 0.51-1.00 mm melanomas and ≥1 mitosis/mm2. In the latter group, the 10-year survival rates dropped to 85 percent if the T1 melanoma was also ulcerated.1

It seems to come from a report co-written by Dr Mihm:

http://www.skincancer.org/publications/the-melanoma-letter/fall-2010-vol-28-no-3/the-revised-melanoma-staging-system-and-the-impact-of-mitotic-rate

What I can’t understand is why would someone with a melanoma thickness between 0.1 and 0.5 with a mitotic rate of one or greater be classified as stage 1b when they have a better 10 year survival prognosis (95%) than someone with a melanoma of 0.51 to 1mm with no mitosis (93%) who would be 1a. It would seem more sensible from this if any melanoma less than 0.5mm was stage 1a and more than 0.5mm was stage 1b. Very confusing.

[cohanja]

I will tell you what I’m curious about from this:

Ten-year survival rates were 97 percent for T1 melanomas 0.1-0.50 mm in thickness and <1 mitosis/mm2

When someone new on this site posts about their pathology being exactly this; 0.1-0.5mm and <1 mitosis. . .we usually tell them it's really low risk, don't worry, the WLE will take care of it, etc. . . but then who are the 3% of T1 melanomas 0.1-0.5mm and <1 mitosis. . that don't survive? What about those 3% made their lesions higher risk?

[Author]

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