Brief Answer:
Either lipoma or sebaceous cyst, but now has some cellulitis.

Detailed Answer:
Hello XXXX,

The location and appearance of the lump could be a lipoma or sebaceous cyst.

A lipoma is a benign fatty tumor. A sebaceous cysts is a cyst that contains or has a collection of oily material. There is a possibility that it was an infected hair follicle that got clogged, but that can just turn into a sebaceous cyst too.

But ... now it looks like the soft tissue around it is infected which is called cellulitis. Treatment for cellulitis is to apply heat, which raises the temperature of the skin, making it an unfavorable environment for the bacteria to multiply in, and also draws white blood cells to the site to help clear the infection.

You can apply hot wet compresses several times a day for a few days. But as it is on your back this may be difficult (compared to a toe, for example, that you can just hold under running water). If it is difficult or if the redness looks like it is spreading, then go to a dr. to get an antibiotic (oral). Antibiotics do not work as well in the skin as they do in a place like the lungs because they don't get in to the skin well. But two good antibiotics for this purpose are Dicloxicillin and Keflex.

If you use a heating pad, be very careful to not burn your skin! Don't go to sleep with it on.

I hope this information helps. Please let me know if I can provide further information or clarification.

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Brief Answer:
May have an access

Detailed Answer:
A lipoma grows very slowly and a sebaceous cyst would not grow exponentially. But if there is an access (a pocket of infection) in addition to the cellulitis (skin infection), then it would be best to go in to a doctor for incision and drainage. This will allow the pus to escape and not reform.

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