Primary versus Metastatic Gastrointestinal Melanoma: A Rare Case and Review of Current Literature

Multiple gastrointestinal melanoma causing small bowel intussusception

A 61-year-old gentleman presented with small bowel intussusception from small bowel melanoma intussusceptum. He complains of intermittent abdominal distension but no history of intestinal obstruction. Apart from this, he was also symptomatic anemia which required repeated transfusion for the past few months. The contrast-enhanced computed tomography of the abdomen shows an omental mass with small bowel intussusception. He then underwent an exploratory laparotomy with segmental resection of the affected segment. Histopathological examination confirmed primary gastrointestinal melanoma. Multiple small bowel malignant melanoma is a rare disease. It remains a controversial diagnosis as it may be a primary or metastasis from an unidentified or regressed primary cutaneous melanoma. Prompt surgical intervention enables us to obtain tissue diagnosis, prevent complete intestinal obstruction and strategize the goals of treatment for the patient.

The different faces of metastatic melanoma in the gastrointestinal tract

Melanoma is the most aggressive form of skin cancer, with tendency to spread to any organ of the human body, including the gastrointestinal tract (GIT). The diagnosis of metastases to the GIT can be difficult, as they may be clinically silent for somewhile and may occur years after the initial melanoma diagnosis. CT imaging remains the standard modality for staging and surveillance of melanoma patients, and in most cases, it will be the first imaging modality to identify GIT lesions. However, interpretation of CT studies in patients with melanoma can be challenging as lesions may be subtle and random in distribution, as well as sometimes mimicking other conditions. Even so, early diagnosis of GIT metastases is critical to avoid emergency hospitalisations, whilst surgical intervention can be curative in some cases. In this review, we illustrate the various imaging presentations of melanoma metastases within the GIT, discuss the clinical aspects and offer advice on investigation and management. We offer tips intended to aid radiologists in their diagnostic skills and interpretation of melanoma imaging scans.

The forgotten appearance of metastatic melanoma in the small bowel

BACKGROUND

Melanoma is the most aggressive form of skin cancer, with a tendency to metastasise to any organ of the human body. While the most common body organs affected include liver, lungs, brain and soft tissues, spread to the gastrointestinal tract is not uncommon. In the bowel, it can present with a multitude of imaging appearances, more rarely as an aneurysmal dilatation. This appearance is classically associated with lymphoma, but it has more rarely been associated with other forms of malignancy.

CASE PRESENTATION

We report a case series of three patients with aneurysmal dilatation in the small bowel (SB) confirmed to be due to metastatic melanoma (MM). All patients had non-specific symptoms; most times being attributed initially to causes other than melanoma. On CT the identified aneurysmal SB dilatations were diagnosed as presumed lymphoma in all cases. In two cases, the aneurysmal dilatation was the first presentation of metastatic disease and in two of the cases more than one site of the gastrointestinal tract was concomitantly involved. All patients underwent surgical resection with histological confirmation of MM.

CONCLUSIONS

Recognition of unusual SB presentation of MM, such as aneurysmal SB dilatation, is important to expedite diagnosis, provide appropriate treatment, and consequently improve quality of life and likely survival of these patients. As the most common cancer to metastasise to the SB and as a known imaging mimicker, MM should remain in any radiologist's differential diagnosis for SB lesions with aneurysmal dilatation.

Case Report: Primary melanoma of the gastroesophageal junction

Primary malignant melanoma represents the fifth most common cancer in the United States. It is subdivided into two forms: cutaneous (90%), visceral (8%, including ocular and mucosal) and of unknown primary (2%). The vast majority of gastrointestinal melanomas are secondary lesions until proven otherwise. Primary esophageal melanoma in particular is exceedingly rare, less than 200 cases have been documented in the literature to date. It is highly prevalent in Japan and occurs twice as much in men than women around the 6th decade of life. It has a predilection for the middle and lower esophagus, with only 6 cases occurring at the gastroesophageal junction worldwide. Its etiology and pathogenesis are poorly understood, and no curative treatment has been established given the paucity of cases. We present a case of primary melanoma of the gastroesophageal junction which represents the 2nd incident case in the united states and 7th worldwide.

Adrenal Gland and Gastric Malignant Melanoma without Evidence of Skin Lesion Treated with the Oncolytic Virus Rigvir

Adrenal gland melanoma is an extremely rare diagnosis with less than 20 cases reported. The criteria for diagnosing adrenal gland melanoma include involvement of only one adrenal gland, presence of melanin pigment in the histological examination of the tumor tissue, no primary melanoma tumor in any other organ, and no history of resection of pigmented lesions. However, it is complicated to rule out melanoma of unknown primary origin. Here we report a female patient who at the age of 75 years was admitted to hospital due to suspicion of adrenal and gastric tumor. The largest tumor was found in the adrenal gland, thus leading to the diagnosis of primary adrenal gland melanoma presenting metastases in the stomach. The melanoma was BRAF wild type. Due to the rarity of this disease, there is no standard treatment. After two subsequent surgeries, treatment with the ECHO-7 oncolytic virus Rigvir was started. The patient has received oncolytic virotherapy for 5 years and 1 month and has been stable since then with good tolerability. The therapy is still ongoing. Adrenal gland melanoma is an extremely rare diagnosis and therefore it is important to discuss the diagnostic criteria and possible treatments.

Primary jejunal melanoma as a cause of adult intussusception: a case report and review of literature

Primary melanoma of the small bowel is a rare clinical entity with a paucity of published reports in literature. Most cases of gastrointestinal melanomas are metastatic lesions arising from skin or ocular origins. This is a case report of a 63 year old female with adult intussusception with jejunal melanoma as the lead point. The index patient had a long history of abdominal pain associated with significant weight loss and presented with features of intestinal obstruction. The possibility of a regressed or unidentified extra-intestinal site cannot be absolutely excluded as the patient did not have a PET scan. Due to the vague nature of clinical symptoms and signs, the diagnosis of small bowel melanoma is difficult, especially in patients with no obvious cutaneous pathology. A high index of suspicion for melanoma as a malignant lead point for adult intussusception should always be entertained.

Primary Mucosal Melanoma of the Stomach

Considered to be rare, mucosal melanomas are rare type of melanoma that are found on mucosal surfaces and are primary or metastatic in origin. We report a case of a 66-year-old Hispanic female who presented with vague abdominal pain and upon further endoscopic work-up revealed 2 gastric lesions. Endoscopic biopsy results revealed gastric melanoma in the distal lesion. A PET/CT scan indicated it to be suspicious for the primary site of metastasis but was ultimately diagnosed as a benign nevus on biopsy. An extensive clinical exam showed no other probable sites of origin. The patient underwent a subtotal Billroth II gastrectomy and enterostomy tube placement for temporary feeding. Primary melanoma of the stomach is an exceptionally rare occurrence with limited cases that can be accounted for in literature; thus we report this case for review.

Malignant rectal melanoma in 2 dogs

Two rare cases of malignant rectal melanoma in dogs are described. Tumors were locally invasive and composed of spindle cells arranged in interweaving bundles, sheets, and nests within preexisting fibrovascular stroma. Mitotic count was high. The diagnosis was achieved based on histopathology and immunohistochemistry for PNL2 and melan-A.