Metastatic Malignant Melanoma of the Gastrointestinal Tract: A Rare Case and Review of Current Literature

Malignant melanoma is the most serious type of skin cancer and it develops from pigment-producing cells known as melanocytes. This neoplasm has a five-year survival rate between 3 to 19% depending on the location and number of metastases. Melanomas typically occur in the skin but may occur in the mouth, intestines or eyes, and rarely, inside the body, such as nose or throat¹.

Malignant melanoma is one of the most common malignancies associated with gastrointestinal (GI) involvement¹. The incidence is 43.5% and is most commonly seen in the liver, peritoneum, pancreas, small bowel, spleen colon, stomach, oral cavity and esophagus¹. Although the incidence of GI metastasis is less frequent compared to the skin, lung and brain, this usually manifests clinically at an advanced stage of neoplasm⁷.

Esophagogastroduodenoscopy is performed in symptomatic patients in order to rule out the disease. Gastrointestinal (GI) melanomas are unusual and once its presence is noted, it requires thorough investigation.

Surgery improves the survival rate significantly in patients with metastatic melanoma to the GI tract, especially when the resection is considered complete following microscopic examination. The median survival after complete resection is 48.9 months, compared with 5.4 months after an incomplete resection. Surgery is also recommended for palliative treatment of GI metastases, with symptom relief reported in the range of 77% to 100% of patients, depending on the site and the reason for resection ^{5, 6, 7}.

This This is a case of a 67-year-old male who presented with a burning sensation in the epigastric area and complained of bloating one month prior to admission. Patient was diagnosed with malignant melanoma with lymph node involvement and pulmonary metastasis 7 months prior to his symptoms. Patient had several episodes of nausea, vomiting and bloatedness; thus, he was referred to the gastroenterology service for further work-up and management. There was no associated weight loss or hematochezia. His family history for cancers was unremarkable. Patient had completed 13 episodes of radiotherapy and this was associated with epigastric burning pain and bloatedness.

In the interim, he had an esophago gastroduodenoscopy which showed multiple flat lesions seen at the body (Figure 1a), antrum (Figure 1b) and at the duodenum (Figure 1c and 1d). Biopsy samples were taken and they showed epithelial cells disposed singly and in nests invading the gastric mucosa. These biopsy findings were consistent with malignant melanoma. Besides melatonin nodules, only erosive gastritis with no ulcers was noted.

Figure 1.(A) Antrum (B) Gastric body (C) 2nd part of the Duodenum (D) Duodenal bulb  

During this admission, the patient was given a proton pump inhibitor, calcium carbonate and simethicone to address underlying gastrointestinal symptoms, which prompted improvement of the epigastric burning pain, bloatedness and nausea. Immunotherapy was initiated with pembrolizumab which the patient tolerated without any adverse reactions.

Unfortunately, the patient had also been diagnosed with Hospital-Acquired Pneumonia (HAP) with pulmonary effusion noted in both lungs. Chest tube thoracotomy was done and antibiotics were shifted. The patient improved and was subsequently, discharged.

Malignant melanoma that involves the GI tract may either be primary or metastatic. Primary GI melanoma can arise in various GI mucosal sites, including the oral cavity, esophagus, small bowel, colon, rectum and anus in the absence of prior cutaneous melanoma¹. Distinguishing between a primary GI mucosal melanoma and a melanoma metastatic to the GI tract from an unknown or regressed cutaneous primary may be difficult. The most common subtype of melanoma, superficial spreading melanoma, is the most common subtype to metastasize to the GI tract although all histological subtypes of cutaneous melanoma may metastasize to the GI tract ^{1, 2}.

Concerning the anatomic site of gastric metastases, the majority of these are reported to occur in the body and in the fundus of the stomach, most often in the greater curvature with lesions in the lesser curvature being very uncommon³. In our patient the lesions were located at the body (Figure 1A), and at the antrum (Figure 1B), as also seen at the duodenal bulb and the second portion (Figure 1C and 1D). CT scans showed metastases noted on the lungs, mediastinal lymph nodes and right hepatic lobe.

Malignant melanoma of the gastric is mostly asymptomatic and it explains why it largely eludes detection. Symptoms include nausea, vomiting, gastrointestinal bleeding, weight loss and acute perforation³. In our patient, he showed nausea, vomiting and bloatedness which was medically controlled. EGD shows only erosive gastritis with no ulcers noted.

The endoscopic classification of gastric metastases comprises three main morphological types. First, melanotic nodules often have an ulcerated tip. Secondly, there are submucosal tumor masses which are elevated and ulcerated at the apex. Third, morphological type is a mass lesion with varying incidence of necrosis and melanosis. In our patient he had the first morphological type^{3, 4}.

The prognosis of patients with metastatic malignant melanoma is poor. Studies suggest a mean survival of patients with systemic metastases from melanoma to be only 6 to 8 months¹. Treatment of metastatic melanoma GI tract may include surgical resection, chemotherapy, immunotherapy and observational trials. The immunocompromised state may cause serious complications in patients with GI tract involvement.

Malignant melanoma has an early tendency to metastasize and has a high mortality rate due to its complications; thus, assessment of metastasis is important and is vital in the treatment and patient’s outcome. Although metastases to the stomach is rare, it is essential to be thorough and include an upper endoscopy to rule out metastatic disease, especially in symptomatic patients.

1. 1.Liang K V, Sanderson S O, Nowakowski G S, Arora A S. (2006) Metastatic malignant melanoma of the gastrointestinal tract. Mayo Clin Proc. 81(4), 511-6.
   Search at Google Scholar

1. 2.Simons M, Ferreira J, Meunier R, Moss S. (2016) Primary versus Metastatic Gastrointestinal Melanoma: A Rare Case and Review of Current Literature. Case Rep Gastrointest Med. 2306180.
   View article·PubMed·Search at Google Scholar

1. 3.El-Sourani N, Troja A, Raab H R, Antolovic D. (2014) Gastric Metastasis of Malignant Melanoma: Report of a Case and Review of Available Literature. Viszeralmedizin. 30(4), 273-5.
   View article·PubMed·Search at Google Scholar

1. 4.Wong K, Serafi S W, Bhatia A S, Ibarra I, Allen E A.Melanoma with gastric metastases. , J Community Hosp Intern MedPerspect 6(4), 31972.
   PubMed·View article·Search at Google Scholar

1. 5.Augustyn A, de Leon ED, Yopp A C. (2015) Primary gastric melanoma: case report of a rare malignancy. RareTumors. 7(1), 5683.
   View article·Search at Google Scholar

1. 6.Genova P, Sorce M, Cabibi D, Genova G, Gebbia V et al. (2017) Gastric and Rectal Metastases from Malignant Melanoma Presenting with Hypochromic Anemia and Treated with Immunotherapy. Case Rep Oncol Med. 2079068.
   View article·PubMed·Search at Google Scholar

1. 7.Alghisi F, Crispino P, Cocco A, Richetta A G, Nardi F et al. (2008) Morphologically and immunohistochemically undifferentiated gastric neoplasia in a patient with multiple metastatic malignant melanomas: a case report. J Med Case Rep. 2, 134.
   View article·Search at Google Scholar