A 60-year-old female shows signs of localized induration and erythema in her right arm after IV placement. What is the most likely diagnosis?

Thrombophlebitis is the most likely diagnosis in this scenario, characterized by localized induration and erythema at the site of intravenous (IV) placement. This condition occurs when a vein becomes inflamed, often due to an underlying thrombus or a reaction to the IV catheter itself. The presentation of localized swelling, redness, and tenderness aligns with the typical signs of thrombophlebitis, especially following an IV insertion where irritation or injury to the vein might have occurred.

In contrast to other conditions, such as cellulitis, which typically presents with more widespread signs of infection, or lymphangitis, which often involves red streaks in the skin and systemic symptoms, the localized nature of the symptoms suggests a specific inflammatory response related to the IV site. Similarly, acute thromboembolism would generally present with symptoms related to a blockage in blood flow, rather than localized signs of inflammation at the insertion point. Thus, the pattern of localized induration and erythema strongly supports thrombophlebitis as the correct diagnosis.