Case Number : Case 870 - 18th October Posted By: Guest

Dysplasia (bowenoid), as supported by the p53, arising within a clonal lesion. The distinct areas would suggest there is a pre-existing clonal seborrhoeic keratosis.

There are things to be considered here but first 2 for me are hidraacanthoma simplex and seborheric keratosis.

Agree with Dr Saleem..

In-situ porocarcinoma arising within a preexisting hidroacanthoma simplex.
I found very instructive the arrangement of the pictures because they show comparatively two populations of cells with distinct morphological appearance, distinct mitotic index and distinct expression of p53.

The neoplastic cells looks Poroid and It seems to have a ductular formation on the lower third of the second picture. Also, as far as I know, p53 is not a good marker to differentiate between an Ecrine poroma and a Porocarcinoma.
Ki-67 index and the histologic findings are compatible with an Hidroacanthoma simplex.

Don't think this lesion is dysplastic. Agree with differential diagnoses above of clonal seb k or intraepidermal eccrine poroma.

Will go with in situ porocarcinoma

I agree with Dr. Saleem: clonal Bowen's disease arising in the context of clonal seborrheic keratosis. The slightly higher cellularity and the parakeratotic/ necrotic focus seen in Picture # 2 together with p53 positivity seen in the majority of the cells in the four nests at the right of Picture # 5 compared with the almost complete negativity in the cell nests at the left are in concert with this diagnosis. An apparent paradox: the p53 positive cells are less Ki67 positive than expected.

Clonal seborrheic keratosis. Clinical is helpful....stable 5 year old lesion.

Agree with the above excellent observations. I agree with Romualdo and Mark that the P53 strong-positive population (right side of IPEX photos) is also paradoxically Ki67 negative, whereas the P53-negative population (left side of IPEX photos) shows a higher (but still unimpressive) Ki67 staining percentage. These two populations show identical low- and high-power features, lacking high grade atypia or (significant) mitotic or apoptotic activity. The cells show simple clear-cell change (clustered in the center of one nest, in the low power first photo)...without definitive poroid differentiation, in my opinion.

This case seems to be a good example of an assertion that P53 and Ki67 are of limited value in differentiating poroma vs. porocarcinoma vs. clonal SK.

[size=3][color=#008080] link: [/color][b][url="http://www.ncbi.nlm.nih.gov/pubmed/21587033"][color=#008080]http://www.ncbi.nlm....pubmed/21587033[/color][/url][/b]
[color=#008080] The "intraepidermal epithelioma" revisited: immunohistochemical study of the Borst-Jadassohn phenomenon.
Lora V, Chouvet B, Kanitakis J. Am J Dermatopathol. 2011 Jul;33(5):492-7. doi: 10.1097/DAD.0b013e3181fe6f9[/color][/size]

[size=3][color=#008080][i] ..."Cell nests in cSK, cBD, hidroacanthoma simplex (HS), and porocarcinoma (PC) showed strong expression of epidermal growth factor-receptors (EGF-R), Ki-67, p63, and p53."[/i][/color][/size]

Shame the nice low powers I also submitted were not included that showed the two lesions incombination. The top two left images are clonal seborrhoeic keratosis (no glands or ducts other than trapped acrosyringia on H&Es and IHC). The top two right images are subtle clonal bowen's disease. What you all missed though was the null p53 on the left supports the diagnosis of Bowen's. The p53 staining on the right is wild type (+30%/++20%, unfortunately the photography greatly over estimates the staining) in a seborrhoeic keratosis. The Ki67 is a little more in the bowen's but not particularly helpful diagnostically other than showing the lesions are different. While diffuse strong p53 can be supportive of Bowen's it is only about 40 to 50% sensitive in my experience. A completely negative p53 (null phenotype) is uncommon but also supports a diagnosis of Bowen's/malignancy. p16 can also be helpful (frequently diffusely strongly positive in Bowen's, negative in seborrhoeic keratosis) but not in this particular case.