Case Number : Case 2592 - 12 June 2020 Posted By: Dr. Richard Carr

Desmoplastik melanoma?

Difficult case. Lymphoid multifocal infiltrate with an intervening cicatricial stroma should aim to a DM, so I favor this diagnosis. But there are some disturbing features: especially the rigenerative rhabdomyoblastic activity in muscle layer... 

I was thinking reticulohistiocytoma 

Mmmm..or..a benign triton tumor?

I saw the pics carefully again and I realise that I made a mistake... those atypical looking large cells I think  are reactive myocytes. The lesion looks infiltrative but there’s marked inflammation along with these reactive myocytes. There’s pink granular material within cells in superficial dermis which resemble like granular cell tumor. 
Thank you for this wonderful case... waiting eagerly for the answer

We've had discussions like this previously. It is not always possible to make a specific diagnosis and we are left with descriptive or speculative report. In the setting of very severe solar elastosis we must consider desmoplastic melanoma (DM) however S100 did not show any spindle proliferation and melanA failed to show features of lentigo maligna. Also this looks like a genuine scar with inflammation. I concluded this was most likely to be a lesion secondary to local trauma such as a bitten lip. The pathology is close to identical to that seen in traumatic eosinophilic granuloma of the tongue (including an eosinophil). There are some quite impressive reactive rhabdomyocytes. 

Update on this case: They had an exophytic but quite symmetrical keratotic nodular lesion that grew in 8 weeks just at the vermillion border of the lower lip and it was punch biopsied (4 weeks before the specimen above). The biopsy was reported by a colleague as favouring a follicular SCC but I've now reviewed the biopsy and I favour keratoacanthoma. So we are looking at the scar from a previous biopsy!!! I should have considered this and the clinical colleague has apologised for not mentioning the previous biopsy! To whet your appetite I've spent a substantial part of the last year refining the diagnostic criteria for KA and have got some astonishing results to share with the dermpath world regarding IHC in KA. The next UK National EQA scheme meeting in November will be devoted to this topic (hosted in Warwick). 

On 17/06/2020 at 14:31, Dr. Richard Carr said:

Update on this case: They had an exophytic but quite symmetrical keratotic nodular lesion that grew in 8 weeks just at the vermillion border of the lower lip and it was punch biopsied (4 weeks before the specimen above). The biopsy was reported by a colleague as favouring a follicular SCC but I've now reviewed the biopsy and I favour keratoacanthoma. So we are looking at the scar from a previous biopsy!!! I should have considered this and the clinical colleague has apologised for not mentioning the previous biopsy! To whet your appetite I've spent a substantial part of the last year refining the diagnostic criteria for KA and have got some astonishing results to share with the dermpath world regarding IHC in KA. The next UK National EQA scheme meeting in November will be devoted to this topic (hosted in Warwick). 

Thank you for sharing such an interesting case!