Case Number : Case 1706 - 12 December - Dr Limin Yu Posted By: Guest

Dr Limin Yu has really set you all a challenge today, get your week of to a great start.

Cheers, Geoff Cross - DermpathPRO Projects

?trichoblastoma/trichoblastic fibroma

Yes trichoblastoma large, pigmented with multiple infundibular cysts

Trichblastoma!!! Great pictures.

Lovely trichoblastoma..

Agree, good example of a trichoblastoma.

Agree trichoblastoma

My first diagnosis is Trichoblastoma, because there are two important clues: cellular balls of germinal epithelium and mesenchymal papillary bodies-like stroma. Also a bit pigment cast fits well, and cystic structures, reminiscent of trichoblastic infundibular cyst.

However I didn't know abdominal wall trichoblastoma in human pathology...but I think this is a reasonable diagnosis. 

Yes, trichoblastoma. Tumor shows the classic dual differentiation toward follicular germinative epithelium, here with different types of arrangement, and toward specific follicular stroma. Just to add a different clue than those kind-heartedly pointed out by Vincenzo, the sharp demarcation between the specific follicular stroma and the surrounding dermis, so the whole tumor could be shelled out.

Trichoblastoma

would appreciate if any of you experts could clarify this: what is the difference between trichoblastoma and trichoblastic fibroma?

Urmila: Trichoblastoma is an encompassing term (usually classified by size or shape of the epithelial component e.g. fenestrated = pinkus tumour; columnar = desmoplastic trichoepithelioma; cribriform when small, mitotically inactive and superficial = classical trichoepithelioma; adamantinomatous = cutaneous lymphadenoma; small nodules, large nodules and grape like [raceiform] nodules etc etc. Trichoblastic fibroma and immature/giant solitary trichoepithelioma are old appelations that are now defunct. Superficial trichoblastoma is often used for lesions seen in naevus sebaceous although other cases form large nodules that can easily be misinterpreted or closely mimic BCC. I'll send you a link to our review on the basaloid tumours - it may help. I tend to use trichoblastoma for mitotically active lesions and commenting that they are benign but may grow to large size but malignant transformation is exceedingly rare. Treatment is simple excision.

2 hours ago, urmilapandey said:

would appreciate if any of you experts could clarify this: what is the difference between trichoblastoma and trichoblastic fibroma?

Trichoblastic fibroma is an old-fashioned term for a trichoblastoma whose stromal component predominate over the epithelial component.

thanks Robledo!

1 hour ago, Robledo F. Rocha said:

Trichoblastic fibroma is an old-fashioned term for a trichoblastoma whose stromal component predominate over the epithelial component.

Thanks a lot for the detailed reply Richard, much appreciated.

Agree with everyone with profound respect!  This is a trichoblastoma. The last two pictures were taken via a small phone to show the very low power impression. 

This case illustrates the flaws in using the "morphological" classification (that can only serve to confuse clinicians) as there are quite large solid areas with rounded undifferentiated morules (trichogerminomatous areas), some cords, racemiform, variable stroma etc. etc.  For report (as a minimalist) I'd suggest just stick with "trichoblastoma" with the comment to the clinician that they are benign, may grow to large size but rarely undergo frank malignant transformation and complete (conservative excision) is recommended in partial biopsy. If "shelled-out" already (as in this case) I'd add a comment there may be a possibility for local recurrence.