Case Number : Case 2425- 16 October 2019 Posted By: Dr. Hafeez Diwan

Solid and cystic hidradenoma.

Agree

It might be a solid and cystic hidradenoma. But the location of the tumor (acral / heel) raises some concerns. I have read somewhere that if you are thinking of a hidradenoma in the acral area, always consider a digital papillary carcinoma. Cases of digital papillary carcinoma can have areas that look exactly like a hidradenoma. Some authors even believe that most hidradenoma of the acral areas are probably digital papillary carcinoma. In this case, I would strongly consider the possibility of a digital papillary carcinoma.

Hidradenoma but complete excision is suggested

I agree with anh

Apocrine Hidrocystoma and Cystadenoma"-like Tumor of the Digits or Toes: A Potential Diagnostic Pitfall of Digital Papillary Adenocarcinoma.

Digital papillary adenocarcinoma usually contains myoepithelial cells, unlike hidradenoma. So a SMA and S100 could be useful...but I favor apocrine hidradenoma(solid-cystic).

Agree with the thoughts above.  The differential is between hidradenoma and digital papillary adenocarcinoma.  P63 can help (if it stains all the cells, rather than the myoepithelial layer then it would favor hidradenoma).  I am wary of calling glandular lesions on the hands and feet hidradenoma, however.  It's possible that these are just variants of digital papillary adenocarcinoma.

Agree, p63 alone would not help because the clear cells in hidradenoma and the myoepithelial cells in the digital papillary adenocarcinoma are both positive for p63.

But if we add a panel of other myoepithelial markers (SOX-10, S-100, smooth muscle actin, or calponin) and EMA (which usually stains only the ductal component and not the myoepithelial cells) , we can see the biphasic nature of a tumor and therefore being able to differentiate hidradenoma and digital papillary adenocarcinoma.

I have reported hidradenoma on the foot and they can have quite carcinoma-like areas due to sclerosis at this location. However this lesion appears to have clearly evident papillary areas and myoepithelial layer so digitial papillary adenocarcinoma (DPA) is strongly favoured. There is recent evidence, from Thomas Weisner's group, (reported in Lisbon ISDP) that HPV42 is +ve in all DPA!  Interesting story that HPV42 a "low-risk" HPV in squamous epithelium has different incorporation in the sweat gland that makes it high risk (E6/E7 viral genes).