Case 11 Male, 13 years. Ulcerating papule, wristShow diagnosis & comments
STUMP (some features of plexiform Spitz naevus, with ulceration)
In this instance, this rather compact proliferation of spitzoid spindled melanocytes, mitotically active and associated with ulceration, forming larger and smaller cell masses and bundles also in deeper parts of the lesion, made me slightly hesitant to diagnose Spitz naevus. Although I favour Spitz naevus, I felt I had to categorize the lesion as STUMP, with an added note that my preferred diagnosis was Spitz naevus. In such situations, I feel it is acceptable to take an expectative approach when surgical margins are free, but in case of positive margins, or doubtful margins, I would advise a conservative re-excision in order to obtain free margins.
Reference on plexiform Spitz naevus:
Spatz A, Peterse S, Fletcher CD, Barnhill RL. Plexiform spitz nevus: an intradermal spitz nevus with plexiform growth pattern. Am J Dermatopathol. 1999 Dec;21(6):542-6.