Case Number : Case 1264 - 28 April Posted By: Guest

Proliferating epidermal cyst.

This tumor shows trichilemmal (pilar) type of keratinization so my diagnosis is proliferating trichilemmal (pilar) cyst/ tumor.

Proliferating trichilemmal cyst

I called this a proliferating tricholemmal tumor with the caveat that morphology is not an accurate predictor of clinical outcome and a recommendation that this be treated as if it were a carcinoma. I completely agree with Dr. Hurt that calling this tumor a carcinoma is a perfectly valid approach as well.

Not surprisingly in this case I would suggest it looks benign and it will almost certainly behave so but local recurrence is a possibility. In the exceedingly unlikely event of a metastasis from this lesion it would not prove malignancy as the operator may have pushed tumour it into vessels during the procedure (assuming the lesion has not regrown and then undergone malignant transformation). Not sure I would be advising a re-excision as it may be shelled-out completely. I confess I have not read the original papers regarding malignant behavior or proliferating pilar tumours that are nicely circumscribed, appear cytologically bland and were adequately sampled (I do note the history might be a concern in this case but surely we should see some morphological evidence to support a diagnosis of carcinoma).