Case Number : Case 833 - 27th August Posted By: Guest

SCC or microcystic adnexal carcinoma arising in organoid nevus

Agree: SCC in sebaceous nevus.

I favor pseudoepitheliomatous hyperplasia of the epidermis and adnexal epithelium. A few mitotic figures can be found, but I’m not definitively persuaded about cytological atypia. The problem here is identify the hidden cause of this reactive reaction pattern.
I’m looking forward to learn if perineural invasion is enough to rule out the diagnosis of reactive hyperplasia.

regressing keratoacanthoma,

I agree with pseudoepitheliomatous hyperplasia with some squamous syringometaplasia. I don´t think that the perineural invasion by squamous cells has relationship with malignant behavior.
I don´t know the diagnosis, maybe an inflamed Epidermal nevus with reactive atypia.

Invasive SCC

I agree with Robledo and Igor. Given the young patient age, I would think this most likely a badly abused verruca, given the hemorrhagic and serous crust, and evidence of dense prurigo nodularis changes in the flanking epidermis (on the far right of first photo). Traumatized epidermal nevus or verrucous SK is also a consideration; clinical history may allow differentiation.
1. [i]Shave biopsy[/i]: The top two photos (shave biopsy) seem tangentially oriented with en-face representation of a reactive basal layer. To me, this looks like reactive/regenerative pseudocarcinomatous hyperplasia secondary to trauma and prurigo changes.
2. [i]Wide excision[/i]: The infiltrative spindled nesting pattern of the lower wide-excision photos seems associated with a regenerating eccrine duct...a regenerative pattern common in wide excisions of previous shave biopsies. Perineural association seems incidental, and does not indicate malignancy in this regenerative context, in my opinion. The infiltrative component appears cytologically similar to the overlying reactive/regenerative epidermis, and lacking in high-grade atypia. The immunostain looks like a double stain for cytokeratin (brown) and S100 (red) with presumed negative staining for eccrine differentiation in the infiltrative component.