Case Number : Case 1009 - 6th May Posted By: Guest

Diffuse granuloma annulare.

Interstitial granulomatous dermatitis, if an underlying systemic illness exists, or interstitial granulomatous drug reaction, if related to pharmacological therapy.

Here are some special stains & techniques:

[img]https://dermpathpro.com/uploads/spot_diagnosis_comment_img/CASE1009_Image%2008.jpg[/img]

[img]https://dermpathpro.com/uploads/spot_diagnosis_comment_img/CASE1009_Image%2009.jpg[/img]

[img]https://dermpathpro.com/uploads/spot_diagnosis_comment_img/CASE1009_Image%2010.jpg[/img]

[img]https://dermpathpro.com/uploads/spot_diagnosis_comment_img/CASE1009_Image%2011.jpg[/img]

These stains point to a diagnosis of dermatofibroma.

Assuming S100 is also negative would go for a dermatofibroma.

Dermatofibroma..

Myofibroblastic dermatofibroma.

My diagnosis was dermatomyofibroma. I thought this lesion had features similar to those published by [url="http://www.ncbi.nlm.nih.gov/pubmed/19155724"]Mentzel and Kutzner[/url] in 2009.

Here is my microscopic description, which should answer the pertinent negatives as well:

"This lesion contains zones of epidermal acanthosis overlying a proliferation of slightly tapered cells in storiform patterns with mostly plump nuclei with a modest amount of cytoplasm forming interweaving zones around the collagen. There is a slight amount of collagen trapping at the periphery. Adnexa are trapped within the substance of the lesion. The CD34 pattern is rarefied in the lesion. Desmin is negative but smooth muscle actin does show a fairly prominent staining pattern in the lesion. PHH3 is essentially nil. There may be perhaps one or two cells in the entire lesion that mark with this mitotic figure marker. I don't identify mitotic figures on the H & E sections. The Factor XIIIa has strong staining in the lesion. EMA is negative as is HHV8 and S100 protein. Elastic fibers are increased on the Verhoeff-van Gieson including some fragmented ones."

Dr Mark, I think dermatomyofibroma has a different morphology with a plaque like dermal growth pattern parallel to the epidermis composed of fascicles of spindle cells with abundant esinophilic cytoplasm. I think the lesion here has a typical morphology of a dermatofibroma with keloidal like collagen entrapped by tumor cells. I believe two components are found in this lesion,a spindle cell one and a histiocytic one. The SMA positivity is reported in some dermatofibromas and I do not think it is against the diagnosis. What do you think?

Dr. Mona, I considered dermatofibroma, and I thought the case was challenging. What surprised me was the similarity of this case to those of Mentzel and Kutzner. I am aware of SMA in some dermatofibromas, but for me this lesion was not completely classical for DF. Perhaps this is an example in which there will be no full consensus. Additionally, before I published the special stains, the diagnosis was considered to be an inflammatory disease, not DF, so this lesion is somewhat unusual for the DF spectrum.

Thanks for your point of difference, Dr. Mona.