Case Number : Case 2338 - 3 June 2019 Posted By: Limin Yu

Benign hamartomatous lesion, most likely fibrofolliculoma/trichodiscoma type lesions.

3 hours ago, HENRY said:

Benign hamartomatous lesion, most likely fibrofolliculoma/trichodiscoma type lesions.

Great point Henry, Agree!

At first glance I was debating if this should be classified as a fibrofolliculoma, or a trichofolliculoma. I looked at the photos hard, and couldn't see any hair bulbs (follicular germ). I think if there is no follicular germ, a lesion should be classified as fibrofolliculoma rather than trichofolliculoma.

Folliculosebaceous cystic hamartoma

Trichofolliculoma vs Fibrofolliculoma.

Agree with the observation of Henry and Zhang. This lesion fit more with Fibrofolliculoma

Dilated cystic structure in the centre along with follicular, sebaceous and mesenchymal elements together suggest folliculosebaceous cystic hamartoma.

Trichofolliculoma

We all agree that this is a form of hamatomatous lesion with both epithelial and mesenchymal components. There are a lot of overlapping histologic features between follicullosebaceous cystic hematoma (FSCH )and Fibrofolliculoma / trichodiscoma. I tried one time to read about these entities and I came to my own conclusion (right or wrong) that FCH  usually has a centrally dilated cystic structure in the center with infundibulocystic and sebaceous differentiation surrounded by mesenchymal storma. The epithelial component is located only in the dermis and not connected to the epidermis.

Fibrofolliculoma /trichodiscoma are also hamartomatous lesions but the epithelial components can be connected to the overlying epidermis and usually not strictly located in the center of the lesion. In fact, the mesenchymal component is more likely located in the center, surrounded by the epithelial component. I was told that the epithelial component in trichodiscoma is more mature then fibrofolliculoma, to wit, has sebaceous differentiation. So if I see sebaceous differentiation, I would classify the lesion as trichodiscoma instead of fibrofolliculoma.

So if I apply my reading to this lesion, I would say that this lesion is completely located in the dermis and the epithelial component in this lesion is in the center surrounded by a mesenchymal storma. There are no epithelial strands attached to the overlying epidermis that I could see. So I would classify it as FSCH.

If someone wants to place this lesion in the Fibrofolliculoma / trichodiscoma group, then it should be a trichodiscoma based on the presence of the sebaceous glands (fig 5).

But that's my own practical approach to this group of confusing hamartomatous lesions. Any suggestions would be greatly appreciated so that I can improve my criteria.

Having learnt the adnexal neoplasm by Requena-Sangueza, I'd rather define this tumor as trichofolliculoma ( sebaceous t. aka FSCH of course ), but I'm learning a lot by Colleagues, so thanks very much.

I believe it is fibrofolliculoma/trichodiscoma

I can't add much!