Although several noninvasive diagnostic techniques for evaluation of skin lesions exist, biopsy is indicated for all suspicious pigmented lesions. Because tumor thickness is often what determines prognosis and treatment, the biopsy technique is critical. For most small and medium-sized lesions the ideal biopsy technique is complete full thickness excision of the lesion
Accurate pathologic interpretation of the biopsy specimen is what helps determines treatment and prognosis.
Several characteristic of primary melanoma tumors help predict the prognosis and risk of metastases. Tumor thickness is the strongest predictive characteristic for recurrence in patients with primary cutaneous melanoma.
Because thickness is so important, melanomas are commonly referred to as thin (generally less than 1.0 mm thick), intermediate (1.0 to 4.0 mm thick) and thick (greater than 4 mm thick).
Melanomas on the arms and legs generally have a better prognosis than those on the head and neck or trunk. Mucosal melanomas have an overall poor prognosis, often because they are detected late. Numerous studies have shown women fare somewhat better than men with melanoma, though the reasons for this are unclear.