Case Number : Case 1646 - 17 October Posted By: Guest

Get your week off to a great start with this interesting Spot Diagnosis Case

Cheers, Geoff

Difficult case. The more than mild sebaceous differentiation with poor germinative component fits better to adenoma... but too much atypia and mitosis and a bowenoid shoulder. So I favor low grade sebaceous carcinoma

It is difficult!!! I am inclined more to call it sebaceous adenoma but if my case will double check with an expert first !!!!  I think the overall sebaceous component is more than the basaloid germinative component. About more than half of the each lobule is mature sebocytes. Very well circumscribed. Not that pleomorphic. Not infiltrative. Giant sebaceous adenomas can be mitotically active. Can mimic BCC clinically also. It is difficult though !! Muir Torre syndrome should be verified.

I thought there was a minimal predominance of immature cells but this is subjective i guess. Atypia is low as well as mitotic index. Tumor is quite lobular but has a marked horizontal extension, picture number 4 shows compromise of epidermis. From my perspective this is sebaceous carcinoma rather low grade. 

This is an ulcerated multilobulated neoplasm focally attached to overlying epidermis with a sharp and pushing boundary to surrounding dermis . there are foci of mitoses but no obvious atypia.normal looking mitoses and ulceration can also be found in sebaceous adenoma.IHC study for ki67,p53 , Bcl-2 and p21 may help to make distinction from low grade sebaceous carcinoma.some intra and peritumoral lymphocytes may point to MTS(?).

overall i lean more toward to sebaceous adenoma.

waiting for Mark's precious idea!

Favor sebaceous adenoma.

I would favour a low grade sebaceous carcinoma. Don't like the atypia. A Ki67 and p53 will be hopefully helpful. To rule out MTS.  Waiting to hear from Dr Hurt.

If this is a sebaceous carcinoma it is clearly in situ (lobulated pushing only borders). Analagous to our concept in follicular SCC in situ. I found image quality sub-optimal to assess the cytology with confidence but I suspect I would have let it go as an adenoma myself based on the architecture.  We should be aware of a difference in individual's approach in this somewhat contentious / challenging area but a mutant / null p53 would certainly pitch the scales.