Case Number : Case 2882 - 23 July 2021 Posted By: Dr. Richard Carr

MAC

At first I thought this might be cutaneous lymphadenoma, especially from the appearance in image 3.  However, on balance I agree with Cem Leblebici that this is more likely microcystic adnexal carcinoma.

FolliculoInfundibular BCC.

Infundibulocystic BCC.

mac

MAC

Well. Positive BerEp4 excludes MAC..CD10 is positive in part stromal and epithelial in another part.. When I saw the case for the first time I was really struggling between BCC and TE! Is this a papillary mesenchymal body in fig 6? Now I am thinking why not it's BCC arising in TE? 

Nice case report!

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6793645/#!po=16.6667

After evaluating immunhistochemistry, I considered basal cell carcinoma with adnexal differentiation. Maybe, it can arise in TE, as Eman El-Nabarawy wrote. 

This neoplasia is enough infiltrative, but radially rather than vertically, as expected in MAC. It’s difficult because there aren’t any epithelio-stromal m. ucin material or clear spaces. At a glance it seemed a lymphoadenoma/TE. However the malignant growth pattern makes me thinking of BCC. 

This was a BCC with some DTE-like areas. Interesting that I did not consider MAC because typical areas of BCC were present (note the nice palisading in 2nd image down on left. It's unusual to see an infiltrative BCC so closely mimic DTE with nice keratocysts and relatively evenly cellular stroma. I suppose we can add also add a nice mimic MAC in view of the responses. BerEP4 was a little variable in the DTE-like areas but more strong and diffuse in the more typical BCC areas (not highlighting lumina only as can be seen in MAC). CD10 shows areas with minimal epithelial staining and other areas with epithelial predominant pattern typical for BCC. No convincing reactive dendritic Merkel cells (which are typically common in DTE). I did not see extra-tumoural perineural invasion in this lesion (just cords sat next to nerves) and it's well to remember DTE may also occassionaly show apparent intra-tumoural perineural invasion (but not extra-tumoural in my experience). For me p16 and p53 were not "aberrant", seems BCC are a little variable in the patterns but do show some nulls for p16 and p53 and some aberrant patterns but also some with wild type patterns. Usually the latter are not required for diagnosis as EMA and BerEP4 sorts out >95% of cases.

59 minutes ago, Dr. Richard Carr said:

This was a BCC with some DTE-like areas. Interesting that I did not consider MAC because typical areas of BCC were present (not the nice palisading in 2nd image down on left. It's unusual to see an infiltrative BCC so closely mimic DTE with nice keratocysts and relatively evenly cellular stroma. I suppose we can add also add a nice mimic MAC in view of the responses. BerEP4 was a little variable in the DTE-like areas but more strong and diffuse in the more typical BCC areas (not highlighting lumina only as can be seen in MAC). CD10 shows areas with minimal epithelial staining and other areas with epithelial predominant pattern typical for BCC. No convincing reactive dendritic Merkel cells (which are typically common in DTE). I did not see extra-tumoural perineural invasion in this lesion (just cords sat next to nerves) and it's well to remember DTE may also occassionally show apparent intra-tumoural perineural invasion (but not extra-tumoural in my experience). For me p16 and p53 were not "aberrant", seems BCC are a little variable in the patterns but do show some nulls for p16 and p53 and some aberrant patterns but also some with wild type patterns. Usually the latter are not required for diagnosis as EMA and BerEP4 sorts out >95% of cases.

Thank u for the interesting case Sir.  I wonder about Bcl2 staining pattern?!

I stopped using Bcl2 around 10+ ago now, CK20 is the most helpful marker for me and careful attention to the 26 criteria of Ackerman. See discussion for case 813 (8 years ago!). In my spreadsheet which I still maintain for interest this case scored -2 (i.e. slight balance of features for DTE) but typical DTE score around -15 on average (all at least -10). DTE-like BCC's score between -2 and +8 (latter a collision of BCC and DTE) i.e. different ball-park. In rare cases when there is genuine significant doubt, recommend complete excision which may require margin control.

great discussion. Thanks Dr Carr!