A nurse is caring for a client with a nevus that has increased in size and changed in color. On examination, the nurse notes an elevated two-centimeter lesion that is dark brownish black in color with irregular borders. The nurse should recognize that these findings are consistent with which medical diagnosis?

A. Malignant melanoma: Malignant melanoma arises from melanocytes and is characterized by changes in size, color, and border irregularity of pigmented lesions. The lesion described—dark brownish-black, elevated, two centimeters, with irregular borders—fits the ABCDE criteria for melanoma (Asymmetry, Border irregularity, Color variation, Diameter >6 mm, Evolution). These indicate a high risk for malignancy and require prompt evaluation and possible excision. B. Kaposi's sarcoma: Kaposi’s sarcoma presents as purplish, red, or brown macules, plaques, or nodules, commonly on the lower extremities, and is often associated with immunocompromised states such as HIV/AIDS. It typically does not arise from preexisting pigmented nevi and usually lacks the dark black pigmentation and irregular borders characteristic of melanoma. C. Basal cell carcinoma: Basal cell carcinoma is a slow-growing malignancy often appearing as pearly or translucent nodules with telangiectasia. It rarely presents as a darkly pigmented lesion and usually does not arise from existing nevi. BCC is more common in sun-exposed areas and tends to ulcerate rather than change color dramatically. D. Squamous cell carcinoma: Squamous cell carcinoma often presents as a firm, red nodule or scaly plaque, sometimes with ulceration. It arises from keratinocytes rather than melanocytes, so lesions are typically not darkly pigmented or black. SCC may develop in areas of chronic irritation or sun damage, but the described lesion’s is more indicative of melanoma.