Melanoma & Critical illness policy claim


I was recently diagnosed with a stage 1a skin malignant  melanoma of 0.3mm.  I have a critical illness policy which says it will cover malignant melanoma but only if it's invaded 'beyond the epidermis'. Does anyone know what this really means in relation to the various staging levels or anyone had a successful pay out on such a policy for a stage 1a case?


Thanks in advance.