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.

Here were my diagnoses:


1st biopsy
SKIN, LEFT CHEEK , SHAVE BIOPSY :
-- SQUAMOPROLIFERATIVE LESION
COMMENT: The lesion extends into the peripheral edge and into the base of the specimen. The findings are not completely diagnostic. Some unusual squamous cell carcinomas and unusual irritated actinic keratoses can have this pattern. However, other types of squamous epithelial lesions, such as pseudocarcinomatous hyperplasia, keratoacanthoma, prurigo nodularis and prurigo en plaque, irritated seborrheic keratoses, some irritated warts, and unusual examples of infundibulitis can have similar features. Further correlation is suggested.

2nd Biopsy
SKIN, LEFT CHEEK , PUNCH BIOPSY
-- SQUAMOPROLIFERATIVE LESION WITH PERINEURAL INVOLVEMENT
COMMENT: The prior biopsy was interpreted by me as “squamoproliferative lesion" with a differential diagnosis of hyperplasia vs. neoplasia. The current case does not have nearly the extensive quality of the prior, but the presence of perineural involvement raises the question about the nature of this lesion being carcinoma. There is a phenomenon that has been described; it is termed "re-excision perineural invasion" but with this phenomenon, especially in epithelial lesions, it is difficult to exclude the possibility of carcinoma mimicking hyperplasia, yet still involving nerves. There are known conditions, especially benign adnexal neoplasms, that can involve nerves, but in the current context, I have to think that carcinoma has to be considered. I showed this case to my colleagues, who thought it was most likely a reactive phenomenon. Despite this, the lesion involves the margins of resection, in addition to the nerve, and I think that some consideration should be given to excising it, as a precaution, if appropriate.

Reference:

Stern JB, Haupt HM. Reexcision perineural invasion. Not a sign of malignancy. Am J Surg Pathol. 1990 Feb;14(2):183-5. PubMed PMID: 2301701.

Thanks for all of your comments!

MAH