Case Number : Case 1555 - 10 June Posted By: Guest

Panfolliculoma.

A Trichoblastoma with distinctive cell balls of pale squamoid cells with peripheral condensation, reminiscent of Trichogerminoma...

I dont find this case easy. My impression is that we see a basaloid neoplasm with mainly a lobular architecture and cord like areas with extensive hyaline material surrounding them. I see some sebaceous ducts and some infundibulocystic areas (or maybe just cystically dilated sebaceous ducts?) there is atypia to my eyes (quite prominent) and mitosis. Some isolated palissading but no retraction artifact and no mucin. The Neoplasm seems mainly dermal but focally connected to epidermis? (lower right corner of first picture). I was thinking of sebaceous carcinoma, ddx with bcc with sebaceous differentiation so would do some immunos EMA, Adipophilin, Ber-ep4, CD10, CK20, P53 would probably throw some neuroendocrine markers too. Trichoblastoma should be a differential but sincerely It was not my first impression, anyways I may be wrong. Really funny perforating phenomenon of the neoplasm, nice case

Basaloid tumour with focal epidermal attachment. Focal, labyrinthine and jigsaw puzzle arrangement along with a predominant multi nodular growth pattern. Not sure if there is definite follicular mesenchyme type stroma. Prominent sebaceous ducts and infundibulocystic structures. No retraction artefact or stream mucin. I haven't seen individual sebocytes (mature/immature). Some of the pictures show overt atypia and brisk mitoses in the busload cells. Agree that we need some IHC (highlighted by Raul).

Could be a sebaceoma/sebaceous carcinoma. Did ponder about a trichoblastic carcinoma. However, would be difficult to diagnose TC in absence of an existing trichoblastoma.

Great, but a difficult case. Waiting for the answer :)

Case c/o Dr George Powell.  My report:

Many thanks for sending this rather wonderful case of a widely trichogerminomatous variant of a large nodular trichoblastoma (benign hair follicle tumour). The diagnosis is supported by condensation of papillary mesenchymal cells (highlighted by CD10 and CD34) in addition to widespread, moderately numerous, Merkel cells (CK20, EMA). In the sections submitted the lesion appears shelled out completely with a narrow soft tissue margin.

Appears I did not photograph the IHC.  Note the lobulated border of the stroma at low power - a typical feature of trichoblastomas. The cell balls here are rather typical of the entity. These lesions often are dominated by epithelium compared with stroma unlike most other TE/TB. In this case the papillary meschymal component is relatively inconspicuous but seen in image 6. There was focal inner root sheath differentiation (not illustrated). Foci of sebaceous differentiation were inconspicuous. The basement membrane thickening is prominent and I think that is exceedingly rare in BCC (I am not entirely convinced by all cases illustrated in the literature - i.e. some of them are trichoblastomas although I don't doubt it can also be seen rarely in BCC).