Atypical fibroxanthoma (AFX) vs mimics (spindle cell melanoma, squamous cell carcinoma, etc)

Here's my sample pathology report template for AFX vs pleomorphic dermal sarcoma: kikoxp.com/posts/5193. A complete organized library of all my videos, digital slides, pics, & sample pathology reports is available here: kikoxp.com/posts/5084 (dermpath) & kikoxp.com/posts/5083 (bone/soft tissue sarcoma pathology).
This video from 2016 discusses the basic workup of a pleomorphic malignant cutaneous spindle cell tumor. The main differential diagnosis includes spindle cell melanoma, spindle cell squamous cell carcinoma, and atypical fibroxanthoma (AFX). Other entities in the differential include leiomyosarcoma, spindle cell angiosarcoma, and (very rarely) cutaneous rhabdomyosarcoma. A panel of S100 protein (or SOX-10), p63/p40 (and/or cytokeratins), desmin, and ERG (or CD31) can essentially exclude most of those entities, leaving only AFX. Some pathologists like to use CD68, CD10, or vimentin as positive stains for AFX. I do not personally like those stains as they are very non-specific and will stain many different tumors, including spindle cell melanoma, spindle cell squamous cell carcinoma, angiosarcoma, and many other tumors. AFX looks histologically identical to undifferentiated pleomorphic sarcoma (UPS...formerly known as MFH). The only way to distinguish between them is to determine the depth of invasion. If the tumor is confined to the dermis, then it has a very low chance of metastasis and is usually regarded as AFX. If it extends into the subcutis, then it likely has metastatic potential and should be considered as a sarcoma. For undifferentiated pleomorphic sarcomas that are confined to the dermis and subcutis on the head and neck of elderly patients, we usually use the term "pleomorphic dermal sarcoma". These may have a slightly lower metastatic potential than large deep undifferentiated pleomorphic sarcomas but can still behave aggressively.
Please check out my Soft Tissue Pathology & Dermatopathology survival guide textbooks: bit.ly/2Te2haB ‬
This video is geared towards medical students, pathology or dermatology residents, or practicing pathologists or dermatologists. Of course, this video is for educational purposes only and is not formal medical advice or consultation.
Presented by Jerad M. Gardner, MD. Please subscribe to my channel to be notified of new pathology teaching videos.
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Please check out my Soft Tissue Pathology & Dermatopathology survival guide textbooks: bit.ly/2Te2haB ‬
This video is geared towards medical students, pathology or dermatology residents, or practicing pathologists or dermatologists. Of course, this video is for educational purposes only and is not formal medical advice or consultation.
Presented by Jerad M. Gardner, MD. Please subscribe to my channel to be notified of new pathology teaching videos.
Follow me on:
Snapchat: JMGardnerMD
Twitter: @JMGardnerMD
Instagram: @JMGardnerMD
Kiko: kikoxp.com/profile/jerad_gard...
Facebook: / jmgardnermd

[@JMGardnerMD]

Here's my sample pathology report template for AFX vs pleomorphic dermal sarcoma: kikoxp.com/posts/5193. A complete organized library of all my videos, digital slides, pics, & sample pathology reports is available here: kikoxp.com/posts/5084 (dermpath) & kikoxp.com/posts/5083 (bone/soft tissue sarcoma pathology).

[@Simon-si3ec]

Thank you Dr. Gardner! Am presenting a case at rounds in a few weeks and this synopsis was most helpful for wrapping my mind around this entity. Love open access medical education

[@JMGardnerMD]

Awesome! I love hearing that. Good luck at Grand Rounds!

[@Simon-si3ec]

Thank you!

[@c.rguez7404]

Thank you so much for this great video Dr. Gardner! Its helped me a lot!!

[@abdullahiahmad3822]

Thanks Jerad. Thats awesome!

[@trishitabhattacharya3189]

Amazing lecture Sir..concepts so beautifully explained

[@drmanimakhija]

Thanks Jerad. Love your talks. Wonder if you could do one on epithelioid sarcoma and pseudomyogenic hemangioendothelioma .

[@JMGardnerMD]

I cover that form of hemangioendothelioma a bit in this video: kzbin.info/www/bejne/e2a0gmaQhK-bpa8. I'll try to do one on epithelioid sarcoma at some point.

[@evelyne7071]

Your lectures have made me very excited in learning about derm-path. Melanoma has always been my “favorite” tumor, because it can look so different one to the other, and because of it’s aggressive behavior (even when small). So, because this tumor was in the melanoma differential, I was anxious to learn more. As a retired cytotechnologist, I of course love it when you go onto high power. In regards to the tri-polar mitotic figure, I was thinking that maybe this mitosis was part of a binucleated cell, where one of the nuclei went into division and the other nucleus just sat there being “pleomorphic”. I cannot see if the cytoplasm wraps around both nuclei. Either way, I appreciated your explanation of the term pleomorphism, as I had never heard it explained so well explained. My question is: Is it possible for one of the binucleated nuclei in a malignant cell to go into mitosis and the other one not do so ? Thank you so much for having rekindled my interest in pathology which I have missed being a part of.

[@JMGardnerMD]

Thanks! And what a great question about if one of the nuclei in a multi nucleated cell can either go mitosis but the others not. I’ve never actually thought about that before! And as far as I can recall, I don’t believe I’ve seen it happening under the microscope. But that doesn’t mean it’s impossible. I’ll be on the lookout for this in the future to see if I can ever spot this happening. Thank you so much for the great question!

[@ilmesmar]

Thank you! ♥️

[@alaelidrissi2207]

Amazing

[@SaviorOfCybertron]

Hornick's book, Practical Soft Tissue Pathology, talks about the "spindle cell variant" of AFX (p.430) saying that these are composed of a monomorphic population of atypical spindle cells, with an accompanying figure that looks much less pleomorphic. How do these differ from the more conventional appearance of AFX that we see in this video?

[@JMGardnerMD]

Yes, some AFX are not as obviously pleomorphic. But they will still usually be a dermal-based spindle cell tumor with some nuclear atypia on the sun damaged head and neck of an older patient. They will also usually have mitoses.

[@anjupandey485]

Awesome 🔥

[@SandhyaRamachandran]

Awesome, as always...u explain beautifully Jerad...wud u consider a fibrosarcoma, monophasic SS, MPNST too?

[@JMGardnerMD]

No I wouldn’t really think of any of those. Fibrosarcoma is very rare, I almost never make that diagnosis outside of a few settings. It usually has a herringbone fascicular pattern. Many other tumors have that same pattern (video coming soon). In the skin, herringbone pattern would make me think of fibrosarcomatous transformation in dfsp. As a translocation sarcoma dfsp, even with fibrosarcomatous transformation, rarely ever has pleomorphism (dfsp video will be created as soon as I can get to it). Same is true of synovial sarcoma...pleomorphism is very rare (see my synovial sarcoma video: kzbin.info/www/bejne/e4O4hXl-f5atkK8); also synovial sarcoma is super rare to involve skin. MPNST has some unique histologic patterns that are often different than those of AFX and again it is extremely extremely rare in skin. See my MPNST video (kzbin.info/www/bejne/a6TddIB9Zqp8d9U) for more details.

[@SandhyaRamachandran]

ohk tats nicely said ! tanq.

[@khawlaalzahra8597]

Fantastic

[@vidyakalla506]

Sir can you explain the concept of malignant fibrous histiocytoma

[@JMGardnerMD]

It is an old obsolete name for undifferentiated pleomorphic sarcoma. A high grade sarcoma that has no obvious type of histologic differentiation.

[@trishitabhattacharya3189]

Sir how much deep should be the lesion to consider it as dermal sarcoma rather than AFX? If we see fat entrapment in the lesion can we call it deep infiltration?

[@JMGardnerMD]

Good question. I don’t know if there is a clear cut answer. If I see fat entrapment (unless its the intradermal fat around adnexa) I will usually call it PDS. If it looks like it’s centered in the dermis and just a few cells trickle into superficial subcutis I might let it go and call it AFX. Depends on the case.

[@trishitabhattacharya3189]

Thanks for explaining Sir

[@dhinchakpillu]

Is CD10 useful in the panel to say its AFX?

[@JMGardnerMD]

No, not in my experience. It’s just too non specific to be of value. Much like vimentin (see my vimentin video: kzbin.info/www/bejne/i3XRoWRqo9OBeZY)

[@kashmisharma6591]

What ihc do u use to confirm AFX??

[@JMGardnerMD]

None. There is currently no reliable specific marker for AFX in my opinion. As I discussed in the video, it is the exclusion of other diagnoses such as spindle cell melanoma and spindle cell carcinoma by immunohistochemistry that allows me to make the diagnosis of AFX.

[@SandhyaRamachandran]

Esp as AFX is a dx of exclusion..TIA.

[@KyrieW]

I am totally the resident who would have said DFSP. Thank you that I never did this in real life! ;)

[@JMGardnerMD]

We've all been there! Until you are taught what these rare tumors look like (and what they don't look like), it's hard to figure out all of the rules for diagnosing them. So glad this video helped you!

[@KyrieW]

Again thanks for posting!

[@lamwlw]

This pace is ok. ~190 words per minute.