Since this has nothing of an actual repercussion medically, you could try saying something in line of abscess drainage or an excision of lipoma/sebaceous cyst, etc.,
NAD ... Tell'em you had a hysterectomy, and then grin and walk away.I get that you'll need to say something because people are like that. But it's not up to you to tell. I, personally, head for "humor" to shut it down.