Study Finds Anorectal Melanoma Is Diagnosed at Later Stages and Is Often Misdiagnosed
Anorectal melanoma is a rare malignant neoplasm that has a variable natural history and nonspecific presentation. A review by Hicks et al of 18 patients treated at Johns Hopkins Hospital between October 1991 and August 2012, finds that the cancer tends to be diagnosed at stage II or later and is prone to misdiagnosis. Although disease-specific survival appears to be better with wide local excision vs abdominoperineal resection, larger studies assessing optimal medical and surgical management of this cancer are needed to improve outcomes. The study is published in JAMA Surgery.
Study Method
The 18 patients in the study had a median age of 64 years, 89% were white, and 56% were male. The presenting symptoms were bright red blood from the rectum (83%), rectal pain (33%), change in bowel habits (28%), rectal mass (22%), nonbloody rectal discharge (11%), and anemia and weight loss (6%). The symptoms occurred over a median of 3 months before patients sought medical evaluation.
Most patients (89%) had an incorrect initial diagnosis, including hemorrhoids (44%), rectal polyp or benign mass (22%), nonmelanotic malignant neoplasms (17%), and adenocarcinoma, small cell cancer, gastrointestinal stromal tumor, and perianal abscess (6% each).
Overall, 56% of the patients presented with stage I disease, 28% with stage II disease, and 17% with stage III disease. Three patients had extranodal disease on preoperative workup, consisting of metastases to the liver and splenic hilum in one patient, liver alone in one patient, and periportal lymph node disease in one patient.
Surgical management consisted of wide local excision in 11 patients and abdominoperineal resection in 7 patients. The median tumor size was 3.0 cm and median tumor depth was 5.5 mm. Among the patients undergoing abdominoperineal resection, 57% were found to have positive lymph nodes, including two patients initially diagnosed with stage I disease. Overall, 28% of patients received adjuvant therapy.
The disease recurred in 11 of 13 patients (85%) with initial stage I or stage II disease within 7.0 months.
Study Findings
Overall, disease-specific mortality was 67%, with a median time to death of 15.5 months (interquartile range = 7.3–25.5 months). Disease-specific survival was significantly longer in patients undergoing wide local excision vs abdominoperineal resection (55% vs 86%, P = .04), although patients undergoing the former tended to have fewer rectal lesions (9% vs 57%, P = .04), smaller lesions (median, 2.5 vs 4.5 cm, P = .02), and a trend toward less advanced stage (stage I in 82% vs 43%, P = .06). Among 14 patients with appropriate follow-up data, 5-year survival was 14.3%.
“Anorectal melanoma is a rare and aggressive malignant neoplasm that is often associated with late diagnosis, advanced stage, high metastatic potential, and high mortality,” concluded the researchers. “In our small series, use of [wide local excision] appeared to be associated with better survival, although the interpretation of this finding is limited by our small sample size and lack of patient standardization. Additional studies assessing optimal medical and surgical management are needed to improve outcomes.”
The authors reported no conflicts of interest.
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