Case Number : Case 555 - 25 July Posted By: Guest

[b][font=arial, helvetica, sans-serif]Pigmented trichoblastoma.[/font][/b]

Basal cell carcinoma, based on the mitoses.

pigmented trichoblastoma

pigmented trichoblastoma

[b][color=#0000ff]Pigmented trichoblastoma. [/color][/b]

[color=#000000]Provisionally, a [b]pigmented trichoblastoma[/b]. [/color][color=#231F20][b]N[b]ests [/b]of basophilic basaloid cells.[/b] [b]M[b]elanin deposition[/b] [/b]is prominent. [b]Mitotic figures[/b] can be frequent in trichoblastomas.[/color][color=#000000] Need to see the [b]low-power view [/b](pattern of growth and in trichoblastomas the tumour is not usually connected to the epidermis), to search for [b]Merkel cells[/b] by [/color][color=#231F20]immunohistochemical markers ([/color][color=#000000]Merkel cells are quite common in trichoblastomas, while basal cell carcinomas generally lack these cells) and to test for [/color][color=#231F20]the immunohistochemical expression of [b]androgen receptor [/b](usually negative in trichoblastomas and positive in basal cell carcinomas). Complete excision is desirable as exclusion of a basal cell carcinoma can be difficult. [/color]

trichoblastoma, pigmented

I like pigmented trichoblastoma, but call my attention some ductal structures in the picture 4 and that make me think in the possibility of an apocrine hidroadenoma, pigmented variant.

Pigmented trichoblastoma is correct. Mitoses are commonly numerous analagous to pilomatsixoma. The lack of retraction artifact and stromal mucin help to differentiate this lesion from BCC. Although you are quite correct in mentioning the role of immunohistochemistry, in my experience it is very rarely required. Certainly, I have never done it. The lesion commonly occurs in nevus sebaceus and this was the case in this example.

Thank you.