Implantation dermoid

[Sameet Memon]

Hello,

We had a patient present with a a palpable lump on volar thumb which had progressively increased in size and had just started causing pain. Pt had his IPJ surgically repaired many years ago.

This was reported as an implantation dermoid which is caused by penetrative injury (in this case, I would assume Pt’s previous surgery). The mass itself is composed of keratin producing, squamous epithelial cells – hence the similar echogenicity to overlying skin. Over time this starts eroding the bone (as seen on x-ray).

The differential would be a glomus tumour which appears similar on x-ray. However, it is an extremely vascular lesion and therefore US can be great to to differentiate.

I found this very interesting so sharing! Steve, please enlighten us with any more info you might have on this 🙂

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[Stephen Bird]

Hi Sameet,

What a wonderful case,

Thanks so much for posting it.

You could put it in the lumps and bumps thread as well if you like,

You have summed it up perfectly and the appearance in your case is typical.

Sometimes these will occur in the sub-cutaneous space area where they are not adjacent to the bone.

In these cases they look much like an epidermoid or sebaceous cyst, however they don’t have a punctum.

Please keep posting your gems,

This one is wonderful,

Steve.

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