Case Number : Case 1835 - 9 June - Dr Richard A Carr Posted By: Guest

Another great set of images from Dr Richard A Carr.

Geoff Cross - DermpathPRO Projects

Bowenoid transformation in Seborrheic Keratosis  

It’s a rare event but the bottom line is: histopathological examination of all SKs should be considered!!!

https://www.researchgate.net/profile/Mehdi_Eftekhari/publication/233984832_Bowenoid_transformation_in_seborrheic_keratosis_A_retrospective_analysis_of_429_patients/links/00463528c711c00f91000000.pdf?disableCoverPage=true

For me there is a component of small cells with high N/C ratio that look poroid. There is also some necrosis en masse and ductular areas, what about CEA expression in this lesion? on the other hand the squamous component looks atypical and has some features of follicular SCC (trichilemmal keratinization and mucin). Architecture looks like well circumscribed/ in situ, I would go with SCC with poroid/ductal differentiation

I thought of follicular SCC

Could this be pigmented hidroacanthoma simplex turning malignant.

https://www.ncbi.nlm.nih.gov/pubmed/?term=Pigmented+malignant+hidroacanthoma+simplex+mimicking+irritated+seborrheic+keratosis.

I thought porocarcinoma. I would do IHQ

I reported this as a rather basaloid (BerEP4-/EMA+), focally pigmented, follicular SCC. The typical features being the rather rounded profile at the peripheries (clinically mimics BCC), abrupt connections with the epidermis and in foci direct connections with follicular infundibula. Absence of adjacent bowen's/AK. Prominent intra-epithelial, stromal type (follicular) mucin and distinctive centrally located pilar type keratinisation. This is really a very typical example of the rather indolent looking, circumscript type, probably mainly an in situ lesion (pushing only borders) and probably does not need follow-up as for "conventional" invasive SCC. A small number of follicular SCC (<10%) in our experience have areas of focally prominent pigmentation with reactive appearing dendritic melanocytes). We have seen one dramatic case that mimicked SSMM clinically and have collected a modest series (as yet unpublished). Perhaps the melanocytes are somehow stimulated in follicular as opposed to "conventional" SCC (actinic keratosis related) in which I have rarely seen pigmentation. Pigmented bowen's is well described particularly in genital locations.