Case Number : Case 1287 - 29 May Posted By: Guest

I thought of bowenoid Porocarcinoma or the squamous variant of eccrine Porocarcinoma in collision with seb k.n

Agree with squamous variant of eccrine porocarcinoma arising in a seborrheic keratosis.

Challenging case ..
Nice differentials.
However, I have a different theory.
Clinically the lesion is papillomatous.
The low power view is of a circumscribed tumor with a rounded profile.
More basaloid.
I can see mucin lakes within the tumor islands and also acantholysis (images 4-6), these two features as I learned from Dr Carr in the last LDS, are clues to follicular tumors such as trichilemmoma, follicular infundibulum lesions (like IFK), and follicular SCC.
The stroma is hyalinized with amorphous collagen, reminding me in the low power image of desmoplastic trichilemmomas, however, I do not perceive peripheral palisading or thick esinophilic BM.
The lesion does not appear to me frankly malignant, however, there is some hyperchromasia and very mild pleomorphism but I can not c any mitoses. May be it is a low grade lesion that I prefer to consider it: follicular SCC (basaloid variant).
I would love to c Ki67.
The 4th image does show in its left upper part, two ductal structures. But I interpretated them as ductal entrapment.
I might be wrong after all :-))

[img]https://dermpathpro.com/uploads/spot_diagnosis_comment_img/Case%201287_RAC7133x5_BerEP4_4pm.jpg[/img]

[img]https://dermpathpro.com/uploads/spot_diagnosis_comment_img/Case%201287_RAC7133x5_p53_4pm.jpg[/img]

[img]https://dermpathpro.com/uploads/spot_diagnosis_comment_img/Case%201287_RAC7133x5_p16_4pm.jpg[/img]

[img]https://dermpathpro.com/uploads/spot_diagnosis_comment_img/Case%201287_RAC7133x5_Ki67_4pm.jpg[/img]

[img]https://dermpathpro.com/uploads/spot_diagnosis_comment_img/Case%201287_RAC7133x5_EMA_4pm.jpg[/img]

[img]https://dermpathpro.com/uploads/spot_diagnosis_comment_img/Case%201287_RAC7133x5_CD34_4pm.jpg[/img]

I am in agreement with Mona's line of thinking.
On the H&E images, I was thinking of an inverted follicular keratosis in the central proliferative area with a differential of follicular SCC.
The immunos show more or less similar profile in the adjacent typical seb k and the central proliferative area. So would stick with Inverted Follicular Keratosis (albeit rather basaloid)!

Nice discussion. Mona I think you nearly nailed it and Arti slammed it home. I called this inverted follicular keratosis (IFK) - all be it rather basaloid! I don't recall seeing one quite so basaloid before but the minimal atypia was against the differential of follicular SCC (really the only differentiating feature). p53 was wild type and p16 is non-specific pattern. I agree Ki67 is in the realm of the seborrhoeic keratosis / IFK. Seborrhoeic keratoses and IFK can be quite mitotic in any case.