Author’s Accepted Manuscript Anorectal Malignant Melanoma Presenting as Acute Pancreatitis Feras Zaiem, Abdulah Alrifai
PII: DOI: Reference:
S0002-9629(17)30131-3 http://dx.doi.org/10.1016/j.amjms.2017.03.006 AMJMS402
To appear in: The American Journal of the Medical Sciences Received date: 1 February 2017 Revised date: 2 March 2017 Accepted date: 3 March 2017 Cite this article as: Feras Zaiem and Abdulah Alrifai, Anorectal Malignant Melanoma Presenting as Acute Pancreatitis, The American Journal of the Medical Sciences, http://dx.doi.org/10.1016/j.amjms.2017.03.006 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Anorectal Malignant Melanoma Presenting as Acute Pancreatitis Feras Zaiem MD1, Abdulah Alrifai MD2 1 Mayo Evidence-Based Practice Center, Mayo Clinic, Rochester, MN Address: 200 1st St SW, Rochester, MN 55902 2 Department of Cardiology, University of Miami /JFK Medical Center Palm Beach Regional Campus, Atlantis, FL Address: 5301 S Congress Ave, Atlantis, FL 33462
Correspondence: Feras Zaiem MD, Mayo Clinic, 200 1st St SW, Rochester, MN 55902. Contact info (E-mail: [email protected]
) and (Telephone number: 507-266-4364).
Conflict of interest: none Source of funding: none Key words: malignant melanoma; anorectal malignant melanoma; pancreatic metastasis; acute pancreatitis.
Malignant melanoma of the rectum is a rare disease accounting for 1% of anorectal malignancies.  It is the third most common location of malignant melanoma after the skin and retina. The disease has a female predominance with a peak incidence in the fifth or sixth decade. Anorectal Malignant melanoma tends to metastasize to regional lymph nodes and liver. We report a unique case of anorectal malignant melanoma with the rare finding of metastases to pancreas, however, the patient was admitted to the hospital for acute pancreatitis. To the best of our knowledge, this is the first reported case of anorectal malignant melanoma with pancreatic metastasis that presented as acute pancreatitis.
A 67-year-old man with no past medical history presented to the emergency department with severe abdominal pain, nausea and intractable vomiting for one week. He also had epigastric tenderness to palpation. Blood test revealed elevated lipase of 1200 U/L and the diagnosis of acute pancreatitis had been established. The patient was admitted to the hospital and had a supportive treatment. The patient is originally from Bangladesh and did not have the appropriate age screening tests for cancers. On physical exam, he has epigastric solid immobile mass and digital rectal exam revealed a solid mass in the rectum at 9 o’clock station with melanotic stool. The patient underwent colposcopy and rectal mass excisional biopsy was consisting with the diagnosis of malignant melanoma. Extensive work up had followed and abdominal computed tomography (CT) scan [Figure 1A] showed multiple large liver metastases with mesenteric lymphadenopathy and enlarged right abdominal mass. Positron emission tomography (PET) scan [Figure 1B] revealed hypermetabolic rectal wall thickening consistent with the site of primary malignancy. It also revealed 1 cm metastasis in the left iliac lymph node and another 3 hypermetabolic masses in the uncinate process of the pancreas that is compatible with metastasis to pancreatic. The biopsy of the intra-abdominal lymphadenopathy was consistent with metastatic melanoma. After a shared-decision making conversation with the patient, he schedule for pancreatectomy in few weeks.
Anorectal Malignant melanoma often presents with painless rectal bleeding and tenesmus and often discounted as being hemorrhoids or polyps. A complete excisional biopsy is required to confirm the diagnosis and the main determinants of prognosis are the depth of invasion and stage of the disease. Subsequently dissemination imaging studies are performed. Almost 60% of patients have already metastases at the initial diagnosis.  Malignant melanoma is reported to 2
metastasize to unusual sites. Liver, inguinal and mesenteric lymph nodes have been reported as the most common sites for metastases, while gastrointestinal (GI) tract and lung metastasis are rare findings.  Given the previous facts, we strongly recommend clinicians that when anorectal malignant melanoma found and diagnosed in a patient, an extensive imaging work up should follow. Very few cases in the literature reported pancreatic metastasis from malignant melanoma. However, to the best of our knowledge, this is the first case of which acute pancreatitis was the chief complaint that led to the diagnosis of anorectal malignant melanoma that had metastasized to pancreas. Pancreatic tumors are commonly primary in origin while secondary (metastases) are rare, accounting 2-5% of all pancreatic malignancies. Secondary pancreatic tumors can present with abdominal pain, jaundice, and weight loss, however, 50-80% has no specific complaints and metastases are incidentally discovered on imaging studies.  Abdominal CT scan can reveal evidence of a pancreatic mass but it is not accurate for distinguishing secondary mass from a primary tumor. Compared with CT, endoscopic US (EUS) has a sensitivity of 95% and specificity of 92% in the evaluation of solid pancreatic masses and can detect very small lesions, two to three mm in diameter.  However, studies have reported that EUS findings of primary pancreatic cancer and secondary are almost similar. EUS-guided FNA is currently considered accurate in distinguishing metastasis in pancreatic from a primary carcinoma. Multimodality treatments of metastatic melanoma to the pancreas have been studied. Pancreatectomy remains the most effective therapeutic option.  It has a good prognosis as a long- term survival have been reported in some cases.  Unfortunately, there are no sufficient data in the literature to compare chemotherapy versus surgical resection in pancreatic metastasis. It is worth mentioning that the United States Preventive Services Task Force (USPSTF) founds insufficient evidence to assess the balance of benefits and harms of using a whole-body skin examination by a primary care clinicians or patients-self skin examination.  However, our patient is a recent immigrant and had never had any screening test. If colorectal cancer screening test -per the USPSTF recommendations - was done, then the anorectal lesion might have been detected and further consequences would have been prevented.
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Figure 1A: Abdominal and pelvic CT scan: liver metastases with mesenteric lymphadenopathy and enlarged right abdominal mass adjacent to the second portion of the duodenum which results in stomach distension.
Figure 1B: PET scan: Hypermetabolic wall thickening of the rectal region consistent with primary malignant melanoma. A one cm left iliac lymph node metastasis and another three hypermetabolic masses in the neck, body and caudal aspect of the uncinate process of the pancreas that is compatible with metastasis to pancreas.