Annals of Oncology Research and Therapy

: 2022  |  Volume : 2  |  Issue : 1  |  Page : 35--37

Primary gastric mucosal melanoma: A rare histopathological diagnosis

Andleeb Abrari1, Fauzia Talat Ekram2, Kafil Akhtar2,  
1 Department of Pathology-Histopathology Division, The Rotherham NHS Foundation Trust, United Kingdom
2 Department of Pathology, Faculty of Medicine, Jawaharlal Nehru Medical College, Aligarh Muslim University, Aligarh, Uttar Pradesh, India

Correspondence Address:
Dr. Kafil Akhtar
Department of Pathology, Jawaharlal Nehru Medical College, Aligarh Muslim University, Aligarh, Uttar Pradesh


Primary mucosal melanoma in the gastrointestinal (GI) tract is very rare, as most of the melanomas diagnosed in the GI tract are metastases, secondary to cutaneous melanomas. We report a rare case of primary gastric mucosal melanoma in a 58-year-old male patient who presented with a short history of upper abdominal tightness and pain for 15 days. Upper GI endoscopy revealed a polypoid mucosal mass with ulceration at the gastric antrum of 2 cm × 2 cm dimension, which was diagnosed histopathologically as malignant melanoma. A detailed clinical and laboratory workup did not reveal any other primary site elsewhere and there was no relevant history suggesting a cutaneous melanocytic lesion. Upper GI endoscopy and microscopic tissue examination with immunohistochemistry formed the mainstay of diagnosis of this exceedingly rare neoplasm.

How to cite this article:
Abrari A, Ekram FT, Akhtar K. Primary gastric mucosal melanoma: A rare histopathological diagnosis.Ann Oncol Res Ther 2022;2:35-37

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Abrari A, Ekram FT, Akhtar K. Primary gastric mucosal melanoma: A rare histopathological diagnosis. Ann Oncol Res Ther [serial online] 2022 [cited 2022 Dec 2 ];2:35-37
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Melanoma represents 1%–3.0% of all malignant cancers and typically appears in sites where melanocytes are commonly found, including the skin, eyes, meninges, and anal region.[1] It is most commonly seen in the rectum and sigmoid colon. Primary gastric mucosal melanoma is a rare disease with 11 cases reported worldwide.[2]

Most melanomas identified in the stomach represent metastases from cutaneous sources.[3] It is found that clinical gastrointestinal (GI) tract involvement secondary to cutaneous melanoma has been reported in up to 4.0% of living patients and up to 60.0% at autopsy.[2],[3]

Although the cell of origin has not been identified since normal stomach epithelium lacks melanocytes, possible etiologies for the occurrence of primary melanoma have been documented. Ectopic migration of melanocyte precursors or differentiation of the amine precursor uptake and decarboxylation cells to melanocytes have been advocated as possible mechanisms for the development of malignant melanoma.[4],[5]

Primary malignant melanoma may be misdiagnosed as other gastric malignant tumor types because of its nonspecific characteristics, so it is not easy to make this diagnosis via clinical or imaging manifestations. In addition, other investigations such as digital GI radiography, computed tomography (CT), and magnetic resonance imaging (MRI) are also helpful in making the diagnosis but require a pathological confirmation.[6],[7]

 Case Report

A 58-year-old male was referred to the surgical clinic with a history of upper abdominal tightness and pain for the last 15 days. The pain was dull aching and nonradiating, insidious in onset, moderate in intensity, and gradually progressive. He also complained of nausea, vomiting, and fatigue, aggravating in intensity over the past 24 h. There was no history of cough, hemoptysis, hematemesis, or weight loss. There was no past history of any treatment or any history of malignant condition in the family members.

Clinical examination was unremarkable with no abnormal pigmentation of the skin or sclera and no enlarged superficial lymph nodes. Ocular fundus was found to be normal and routine examination of the chest, cardiovascular, and abdominal cavity revealed no abnormality. Routine hematological investigations and urine examinations were found to be within normal limit, except for mild anemia. CT scan of the abdomen revealed a small, heterogeneous, solid mucosal mass in the gastric antrum with no lymph node enlargement.

Endoscopic examination of the upper GI tract revealed a polypoid mucosal mass with ulceration at the gastric antrum of 2 cm × 2 cm in dimension. Endoscopic biopsy was performed. Microscopically, the tissue section revealed proliferated mucosal glands with foci of ulceration with sheets of pleomorphic cells. The tumor cells were round to polygonal with large nuclei, prominent eosinophilic nucleoli, and moderate amount of granular eosinophilic cytoplasm with subtle and faint brown pigmentation [Figure 1]a, [Figure 1]b, [Figure 1]c. Immunohistochemically, the tumor cells showed strong cytoplasmic positivity for Melan-A protein [Figure 1]d and HMB-45 [Figure 1]e and strong nucleo-cytoplasmic positivity for S-100 [Figure 1]f staining, thus, confirming the diagnosis of primary gastric mucosal melanoma. Other immunomarkers including the cytokeratins (Cam 5.2, CK7, and CK20), EMA, CDX2, HepPar1, TTF1, chromogranin, synaptophysin, DOG1, CD34, LCA, CD30, CD20, CD3, and TFE3 were negative. Our patient was administered standard 50 Gy of cobalt-60 adjuvant radiotherapy. He remains completely symptom-free and well 6 months into follow-up. A surveillance colonoscopy is planned at 1 year.{Figure 1}


Malignant melanoma most commonly develops in the skin. The vast majority of GI melanomas are metastases from a cutaneous primary tumor.[3] Approximately 92.0% of melanomas are cutaneous and only 1.2% are noncutaneous melanomas located in the mucous membranes.[5] Primary GI malignant melanoma is an unusual rare clinical entity. The most common etiology associated with cutaneous melanomas is exposure to ultraviolet radiation. One of the possible suggested mechanisms of its origin is from the ectopic melanocytes, which migrate to the digestive tract during embryogenesis.[8]

Primary gastric mucosal melanoma is underdiagnosed, its symptoms and signs are nonspecific and the clinical manifestations are similar to those of other gastric tumors.[9] Most patients are asymptomatic until the tumor becomes advanced. The common presenting features are abdominal pain, nausea, vomiting, weight loss, and upper GI bleeding.[10] Our patient presented with abdominal pain which was insidious in onset and gradually progressive in nature associated with nausea and vomiting.

Upper GI endoscopy with subsequent histopathological examination of the retrieved specimen can lead to a confirmatory diagnosis.[6],[7] On upper endoscopy, a mass-like lesion with black pigmentation may be seen. Immunohistochemical stains with melanocytic markers – S-100, Melan-A, HMB-45, and SOX10 have increased the diagnostic sensitivity of biopsy and cytology and play a key role in the diagnosis of these lesions.[7] Upper GI endoscopy in our case showed a pigmented polypoid mucosal lesion of 2 cm × 2 cm in dimension with focal ulceration at the gastric antrum. Microscopically, the tissue section of the biopsy specimen revealed pleomorphic cells arranged in sheets with large nuclei and moderate amount of eosinophilic cytoplasm containing dark brown pigments. Positive immunohistochemical staining for HMB-45, S-100, and Melan-A confirmed the presence of morphologically malignant melanocytes in the mucosa. Other immunomarkers were performed, as stated earlier and were found to be negative. Particularly relevant was the negativity for the cytokeratins, EMA and CDX2, ruling out an epithelial neoplasm; negative neuroendocrine markers and no expression of TFE3, which excluded a perivascular epithelioid cell neoplasm, which carries some immunohistochemical overlap with melanoma.

Imaging studies are of great value in melanoma diagnosis. Digital GI radiography can clearly reveal the shape, location, and size of upper GI tumors. It also can be used to dynamically observe gastric wall peristalsis and digestive tract obstruction. CT can be used to evaluate the feasibility of excision of gastric tumors and is a useful and crucial method of monitoring recurrences or metastases during follow-up. MRI signal intensity can be used to evaluate melanin-containing gastric melanoma.[4],[10]

Criteria for the diagnosis of primary gastric mucosal melanoma include the absence of concurrent lesions and the lack of a history of melanoma or atypical melanocytic lesion removal from the skin or other organ.[7],[8] Care must also be exercised to exclude secondary visceral involvement in cases of clear cell sarcomas of soft parts, which in essence are but melanomas of soft tissue.

There is no standard protocol for the treatment of primary gastric mucosal melanoma. Surgical resection and a combination of different adjuvant therapies are reasonable options, and the choice of treatment should be individualized for each patient. Tumor resection shows the best results.[5] Other therapeutic options are chemotherapy, which includes gamma interferon and interleukin-12.[10] Most researchers believe that radiotherapy has only a palliative role, as melanoma is nonsensitive to radiation.[8],[9] Prognosis is extremely poor due to delay in the diagnosis, an inherently more aggressive behavior, and earlier dissemination because of the rich lymphatic and vascular supply of GI tract mucosa.[10] It has been reported that the median overall survival associated with primary mucosal melanoma of the GI tract is 17 months, whereas that associated with primary gastric mucosal melanoma is only 5 months.[9],[10]

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.


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