MSRA-1001

A 78-year-old woman presents to her general practitioner with a painless lump in her groin that she noticed 2 weeks ago. The lump has grown slightly since she first noticed it. On examination, a hard lump is palpable on her left labia majora and she has left inguinal lymphadenopathy. She has no significant past medical history and no known allergies.
What is the most probable diagnosis?