Clusters of small lumps in cat's armpits.

Amber and I were having our morning snuggle in bed this morning and while I was rubbing under her chin and on her chest I felt small clusters of lumps under her armpits. They are only small almost like eczema.
I have noticed that she is grooming a little more than usual. She is 2 years old, wormed and de flead. She is indoor with an enclosure in the garden and eats a wet food diet which hasn't changed since we have had her. Her coat is semi long hair and is still shiny and healthy. My other cat Sasha is fine.
She is due her annual check up next week so I will be discussing this with the vet but was wondering if anyone had experienced anything similar.

Well, since you are just days away from your vet appt., you probably can wait on this. Are the the tiny lumps visual to the eye OR are they under the skin? You mention such as eczema so I am thinking they are not internal but external little lumps. Could be bug bites, flea dermatitis since the cat goes on in the garden, or a skin allergy beginning and developing into a rash. I have not ever heard of a cluster of tiny lumps under the skin, not visual, so I am thinking these are external. Wish I could be of more help! But, please inform us what your vet diagnoses! Good luck!

Does your flea med kill ticks too? Id be concerned they could be something like deer ticks, if they're external.

Thanks for the replies.
Since posting these lumps seem to be disappearing on there own. I'm inclined to think that they were a flea allergy type reaction, being in the armpit too. Years ago we had a cat with flea allergy and it seemed to feel similar to that. My cats and our resident stray were all treated just over a week ago with an all in one flea, tick and worm medication. I don't think it was a reaction to the actual medication as I it would have been the site of application that would have been affected.
I'm just glad that they are disappearing on there own but I will chat to the vet about it and let you know what he thinks.
Thanks again!