Erysipelas — Streptococcal Skin Infection

A 45-year-old man with a history of tinea pedis presents with abrupt onset of fever, chills, and a painful erythematous plaque on his left lower leg. On examination, the lesion shows a brilliantly red, warm, tender area with a sharply demarcated, raised border (marked **B** in the diagram) separating it from adjacent normal skin. Regional lymph nodes are enlarged and tender. Which of the following clinical features is MOST directly explained by the sharply demarcated, raised border characteristic of the structure marked **B**?