Based on the above images, what is your first impression?
* Dermatofibrosarcoma protuberans
^Pleomorphic dermal sarcoma
* Dermatofibrosarcoma protuberans
^Pleomorphic dermal sarcoma
S100 and SOX10 
CD34 ❌
CD10 ❌
HMB45 ❌
CD10 ❌
HMB45 ❌
What are your thoughts now?
* Malignant Peripheral Nerve Sheath Tumour
^ Pleomorphic dermal sarcoma
* Malignant Peripheral Nerve Sheath Tumour
^ Pleomorphic dermal sarcoma
Melan A and HMB45
PRAME
Adjacent to lesion
HMB45/ Melan A/ PRAME
⚕️Diagnosis:
🔬Spindle cell melanoma
🔬Spindle cell melanoma
Question
Which if the following is true of spindle cell melanomas?
Which if the following is true of spindle cell melanomas?
1/ These tumours are more common in sun effected areas (although any skin site can be affected).
2/ They tend to occur in Caucasian males in the 6-8th decade of life.
pubmed.ncbi.nlm.nih.gov/30250577/
2/ They tend to occur in Caucasian males in the 6-8th decade of life.
pubmed.ncbi.nlm.nih.gov/30250577/
Question
True or false?
Spindle cell melanomas (SCM) are a variant of desmoplastic melanomas (DM).
True or false?
Spindle cell melanomas (SCM) are a variant of desmoplastic melanomas (DM).
3/ SCM ae thought to be a distinct entity with different mutations and prognosis.
4/ A suggestion is that a tumour should only be called a DM "if a significant part of the tumour is associated with and dispersed in a dense fibrous stroma".
nature.com/articles/modpa…
4/ A suggestion is that a tumour should only be called a DM "if a significant part of the tumour is associated with and dispersed in a dense fibrous stroma".
nature.com/articles/modpa…
Question
Which of the following is true of SCM and their immunohistochemistry/special stains?
Which of the following is true of SCM and their immunohistochemistry/special stains?
5/ SCM usually have strong S100 and SOX10 expression.
6/ Like DM, they can lose HMB45 and Melan A (although less so).
7/ Trichrome stain (see previous article) is useful for DM.
8/ The video below is super useful, cheers @JMGardnerMD !
6/ Like DM, they can lose HMB45 and Melan A (although less so).
7/ Trichrome stain (see previous article) is useful for DM.
8/ The video below is super useful, cheers @JMGardnerMD !
Question
True or false?
The newish marker, PRAME (PReferentially expressed Antigen in Melanoma), is specific for melanoma?
True or false?
The newish marker, PRAME (PReferentially expressed Antigen in Melanoma), is specific for melanoma?
9/ PRAME can be useful to help distinguish melanocytic nevi ❌ vs melanoma✅
10/ However, it is more marker of malignancy & not specific for any particular tumour (NB sebaceous glands are ✅)
11/ It can be expressed in many tumours, including sarcomas
pubmed.ncbi.nlm.nih.gov/36102613/
10/ However, it is more marker of malignancy & not specific for any particular tumour (NB sebaceous glands are ✅)
11/ It can be expressed in many tumours, including sarcomas
pubmed.ncbi.nlm.nih.gov/36102613/
Last question
Which of the following genetic mutations is more common in SCM?
Which of the following genetic mutations is more common in SCM?
12/ The below study showed that BRAF V600E was the most common mutation in SCM (there are others with smaller numbers out there which differ).
13/ Interesting DM tend not to have BRAF mutations, so another difference!
pubmed.ncbi.nlm.nih.gov/22809251/
13/ Interesting DM tend not to have BRAF mutations, so another difference!
pubmed.ncbi.nlm.nih.gov/22809251/
Spindle cell melanomas on twitter:
https://twitter.com/JMGardnerMD/status/1609667744865165312?s=20&t=uHW0rkLv3PZkwG3_A5JrJQ
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