Case Number : Case 2099 - 22 June 2018 Posted By: Dr. Richard Carr

 Trichoblastoma

Rippled pattern trichoblastoma

Favor trichoblastoma

I’m concerned about bcc adjacent to trichoblastoma.  Would like to see a broader field on the CD10 immunostain.

Agree with Trichoblastoma!

Agree  with Trichoblastoma.  I got to admit I rarely use immunos to diffentiate trichoblastoma from BCC or SCC so I have almost no experiences. Now that we have these beautiful immuno figures, could Dr Carr give us a short summary how to use immunos in these cases. I read  Dr. Carr’ comments on these immunostains in many cases before and seems Dr. Carr has a better understanding than any of us how to use these immunostains for these types of lesions.

I think the CD10 pattern is more with BCC. Also the CD56 expression. 

Infundibulocystic Basal cell carcinoma.

This is a ripple-pattern lesion. The differential diagnosis includes sebaceoma or basal cell carcinoma. Ackerman emphasizes the association of ripple pattern with sebaceoma over trichoblastoma https://www.derm101.com/dpc-archive/october-december-2001-volume-7-no-4/dpc0704a03-ripple-pattern-signifies-sebaceoma-not-trichoblastoma-or-trichomatricoma/. Kazakov also associate the ripple pattern with sebaceoma. In this case the lack of well-formed follicular germ (to my eye), the positive CD10, the lack of Merkel cells, and the patient's relatively advanced age, makes me worry about a basal cell carcinoma. I am curious to know if there are any sebocytes in the lesion. But irregardless I would recommend excision of the lesion.

Thanks for the suggestions. In my opinion this is a rather wonderful example of an unusually predominantly "labyrinthine" pattern of BCC. Remember my usual comments that for every 20 basaloid tumours on sun-damaged skin of older patients that show some resemblance to a trichoepithelioma/TB 19 will be BCC in practice. Usually TE/TB will be at least 50% stroma compared with epithelium unlike BCC where epithelium is normally >75%. I find these simple IHC's very useful. BCC so often diffusely positive and EMA negative in the basaloid areas. CD10 is helpful to the specific differential here and epithelial predominant pattern favours BCC. Merkel cells are rarely if ever seen in BCC and are numerous or widely scattered in just over 30% of TE/TB. CD56 was performed by the referring pathologist who obviously considered neuroendocrine differentiation (NED) but as you know NED is frequent in BCC. When you see the rippled or indeed labyrinthine pattern consider sebaceous lesions or indeed differentiation towards the follicular mantle which is what I think this case shows. I suspect if we had adipophilin we might even find some sebaceous differentiation although I could not confirm it on H&E or EMA. In our experience sebaceomas are BerEP4 negative although I'm not sure I specifically studied the labyrinthine type.

Yes! I was wrong. This case has been useful for me. Thanks Dr Richard.