7. Primary cutaneous melanoma 90% Primary non cutaneous melanoma 10%
Melanomas originate from melanocytes which are derived from embryological neural crest cells
Primary cutaneous melanoma 90%
Primary non cutaneous melanoma 10%
Uveal & retinal
Rectal
Prostatic
Urethral
Sinonasal
Metastatic

8. PRIMARY ANORECTAL MELANOMA
Arise from dentate line, the transition zone & squamous zone
On cross sectional imaging
bulky, intraluminal, poypoidal or fungating masses in the distal rectum, focally expanding & obscuring the lumen
No significant obstruction
Perirectal infiltration peri rectal enlarged lymph nodes

9. MRI MRI local staging as extraluminal extent is better assessed
MRI is helpful to detect melanotic component which is high on T1w due to free radicals of paramagnetic substances
Other rectal lesions do not have melanin hence are low on T1
Exceptions occur as 10 to 30 % melanomas are amelanotic
Melanomas are hypervascular & they may bleed . Acute bleed is also on T1w and they show avid enhancement on post contrast images

10. COMPUTED TOMOGRAPHY
Contrast enhanced CT scan analyze gross extent of primary disease, not only extension into perirectal space but invasion of adjacent organs, involvement of regional and distant lymphnodes and distant mets

11. At the time of diagnosis 26 -38 % patients show metastasis Mets go to
lymphnodes (mesenteric, inguinal, hypogastric, paraortic regions)
Liver
Lung
Skin
Brain

23. AMERICAN JOINT COMMISSION ON CANCER STAGING SYSTEM FOR ANORECTAL MELANOMA
Stage IA localized mm depth
Stage IB localized mm
Stage IIA localized mm
Stage IIB localized > 4 mm
Stage III regional nodes any depth
Stage IV distant mets any depth

24. THANKYOU