Case of the Month

A 50-year-old man presents with "a bump on the back of my hand that I can move all around under my skin." He reports no pain unless the bump is pushed on very firmly. He noticed the lump about a year ago. He has no medical history significant for this lesion. He is a carpenter.

What's Your Diagnosis?

Diagnosis: Mobile Encapsulated 'Pea-Sized' Lipoma

I have seen many of these over the years, but I did not know what to call it. They have no attachment to any vascular source and appear to be more fascinating that problematic/worrisome. After some research, I found that this lesion has been called many things, including: nodular-cystic fat necrosis, mobile encapsulated lipoma, encapsulated fat necrosis, and encapsulated necrosis. Some report the development after trauma. Many patients do not recall any trauma, but as this patient said, "I am a carpenter, I bang my hands all the time." I prefer the term Mobile Encapsulated 'Pea-Sized' Lipoma' because it is much smaller than the traditional lipoma. Perhaps an alternative name is Mobile Encapsulated Small Lipoma, but Mobile Encapsulated 'Pea-Sized' Lipoma gives one a much better idea of the true size, and all that I have seen are "about "pea-sized," as shown in the photo.

I did the lesion's excision, so the photo is of the actual lesion he was pushing around. My good friend Eric Jacobson, MD, was kind enough to do the pathology and send the excellent photomicrographs.

Reference

Mobile Encapsulated Lipoma
Nodular-Cystic Fat Necrosis