Primary Melanoma of the Anus
Definition
- Primary melanoma arising in the anus
Alternate/Historical names
- Anorectal melanoma
Diagnostic Criteria
- Histologically identical to cutaneous melanomas
- Patterns described:
- Epithelioid
- Spindle cell
- Lymphoma-like
- Pleomorphic
- About half may be amelanotic
- Junctional component identifiable in about half of cases
- Careful analysis of location indicates that the vast majority of anorectal melanomas actually are anal
- True rectal melanoma is exceedingly rare
- Metastasis must be ruled out clinically or by identification of a junctional component
- Poor prognosis
- Most recurrences are systemic
- 5-25% 5 year survival
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
Original posting/updates : 10/7/10, 11/13/11
