Young dog with peculiar skin mass

Vaccine hypersensitivity reactions aren't super common, but they do occur.

There are actually a number of different ways a pet can develop a reaction to a vaccine. But in this case, I show you a type 4, delayed-type hypersensitivity response and what it looks like cytologically.

This is a 2 year old male castrated dog who presented to his vet with a small mass on the shoulder area.

Check it out!