Case Number : Case 2259 - 8 February 2019 Posted By: Dr. Richard Carr

Bowen's

Bowen with trichilemmal differentiation or a Trichilemmoma with atypia (Trichillemal carcinoma "in situ"??)

It will be very interesting read more opinions.

Nice, with the immunos, trichilemmal carcinoma in situ?

Follicular squamous cell carcinoma in situ with trichilemmal differentiation.

From low power, it just looks like an irritated trichilemmoma with some warty features (or somebody would call it verruca with trichilemmal differentiation). but high power views do show cytologic atypia with higher levels of mitoses. In daily practice, for a patient age 85, I may just sign it out as Bowens and move on to next case. 

Trichilemmal carcinoma is described as a predominantly intra epidermal growth, often with pushing invasive component, in new McKee's book. There are large cells with diastase-sensitive Pas+ clear cytoplasm, and many mitosis. CD34 is typical. Some micro invasive component in fig4. So why not a well differentiated trichilemmal carcinoma, according with Mona and Alex-Ventura? Thought also of ISK, but TC is my favorite spot.

I still believe this is only a trichilemmoma, maybe as Henry said, irritated trichilemmoma.

Cutaneous horn overlying a trichillemal carcinoma

Just to add more confusion: is there a chance that we can entertain the idea of actinic keratosis arising in a trichilemmoma?

I thought this was a tricholemmoma with cellular atypia amounting to dysplasia. I reviewed the literature on tricholemmal carcinoma extensively in the past and they were not CD34 positive and did not show basement membrane prominence. I think you can see cellular atypia is older patients that is of doubtful significance and perhaps that is the case here. Sorry I can't be definitive in this case.