Deep penetrating naevus-like borderline tumour/ deep penetrating melanocytoma (updated WHO nomenclature)

Case 2498  3.2.20 

Ref: Eur J Dermatol 2014: 24: 594-602.   Wedge-shaped or plexiform growth pattern.  Deeply pigmented spindle and epithelioid cells often extending into fat. 

Ref: DPN first description Seab JA. Am J Surg Pathol 1989 13: 39-44 

Case 2706 19.11.20 (S. Taibjee) F 66 pigmented lesion thigh ?MM 

This was a difficult lesion requiring several opinions. 

ST: “DPN is usually an intradermal lesion, but not infrequently it can be associated/combined with another lineage to account for an associated junctional component. A degree of cytological atypia is allowable within DPN, and should not lead to an overdiagnosis of malignancy.” 

Case 3001  6.1.22 (S. Taibjee)  M 57 pigmented lesion, thigh 

This lesion has some worrying features such as cellular pleomorphism, phenotypic variability, scattered motises, focal perineural extension and also evidence of having arisen from smaller conventional naevus 

IHC: Betacatenin +ve (nuclear in DPN; cytoplasmic in naevus); PRAME +ve; BRAF +ve (this pattern worrying, suggesting MELTUMP appellation)