Thread by @TristanRutland7

Skin, Young adult

#Dermpath #BSTpath #pathtwitter

Based on the above images, what is your initial impression?

*Dermatofibrosarcoma protuberans

Immunohistochemistry:

CD34

⚕️Diagnosis:

🔬Dermatofibrosarcoma protuberans (DFSP)

True or false?

Paediatric DFSP, although rare, are very aggressive compared to adult tumours.

1/ This locally aggressive fibroblastic tumour classically occurs in young to middle aged adults.

2/ Cases can occur in children, but the study below (luckily) showed 0 mets in 15 cases (over 2 years) (1 recurrence due to inadequate margins and delay).

pubmed.ncbi.nlm.nih.gov/21429521/

Question:

The so called “Bednar tumour” is a type of DFSP that shows?

3a/ There are a number of different variants of DFSP, which include:

💦Myxoid➡️ their myxoid

🥏Plaque-like ➡️ they are flat…

🎨Pigmented (Bednar tumour) ➡️ you guessed it

⚠️Fibrosarcomatous ➡️ can arise in recurrences (or de novo in existing DFSP).

pubmed.ncbi.nlm.nih.gov/3901787/

Question:

Classic DFSPs have an architecture that is best described as?

3b/ The classic DFSP has a storiform or 🍥whorled like architecture.

3c/ Where is infiltrates into fat it can have a 🐝honeycomb appearance (below examples).

3d/ Fibrosarcomatous DFSP has 🐟herringbone areas.

Question:

In fibrosarcomatous DFSP (FS-DFSP), half of these tumours show expression of?

4/ The study below (a bit old now) found that only 15/33 of the fibrosarcomatous areas were positive for CD34 (sort of a trick question...).

5/ Important to be aware of this as negative staining for CD34 does not exclude a FS-DFSP.

pubmed.ncbi.nlm.nih.gov/9591728/

Question:

Most DFSPs have which translocation?

6/ Like many blandish/monotonous tumours, DFSP have a characteristic COL1A1-PDGFB fusion.

7/ A smaller portion (~4%) have other fusions including PDGFD.

8/ FISH is useful for FS-DFSP cases (esp where CD34 is negative).

pubmed.ncbi.nlm.nih.gov/29955147/

Question:

Lastly, which drug has had some success in treating metastatic DFSP?

9/ Along with radiotherapy, Imatinib (a tyrosine kinase inhibitor that targets PDGFR) has had some success in treating metastatic DFSP.

10/ The discussion in the below paper is really good (imo), especially about histological response to treatment.

pubmed.ncbi.nlm.nih.gov/30601909/