Which of the following is NOT a malignant lesion?

Erythema migrans, often referred to as geographic tongue, is considered a benign condition characterized by patchy loss of the protective layer of the tongue's surface, leading to a map-like appearance. This condition is typically asymptomatic and does not pose a risk of malignancy. It is more related to geographical and genetic factors rather than being an indicator of cancer.

In contrast, leukoplakia is a condition that can potentially become malignant, particularly if atypical cells are present upon biopsy. Squamous cell carcinoma is a well-known malignant tumor that arises from squamous tissues, most commonly associated with the skin and mucous membranes. Melanoma, another malignant condition, specifically refers to cancer arising from melanocytes, the pigment-producing cells in the skin.

The key aspect to understand about this question is distinguishing between benign and malignant lesions. Erythema migrans is entirely benign and does not have a cancerous potential, making it the correct choice when identifying which lesion is not malignant.