Myxoid Spitz nevus.
BACKGROUND
The deposition of extracellular mucin has not been described in Spitz nevus and herein such a case is reported.


METHODS
A 6-year-old male presented with a growing 1.0-cm pigmented lesion on his left anterior knee. The lesion was excised.


RESULTS
The histologic sections demonstrated a symmetrical and dome-shaped proliferation of spindle and epithelioid melanocytes with sharp lateral demarcation at the dermal-epidermal junction and within the superficial dermis. Features of Spitz nevus such as retraction from the epidermis, eosinophilic bodies, and uniform cytologic atypia were seen. Of interest, there was marked mucin deposition within the epidermal clefts and between the neoplastic cells. The mucin was highlighted by alcian blue and colloidal iron stains, and it was negative with mucicarmine and periodic acid-Schiff stains.


CONCLUSIONS
Awareness that soitz nevi can rarely have extracellular mucin helps in avoiding diagnostic pitfalls.
D002648:Child; D003937:Diagnosis, Differential; D005110:Extracellular Space / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D007717:Knee / Q000473:pathology; D008297:Male; D008544:Melanocytes / Q000378:metabolism / Q000473:pathology; D008545:Melanoma / Q000473:pathology; D009077:Mucins / Q000378:metabolism*; D018332:Nevus, Epithelioid and Spindle Cell / Q000378:metabolism / Q000473:pathology*; D012878:Skin Neoplasms / Q000378:metabolism / Q000473:pathology*
D009077:Mucins