Rare Case of Primary gastrointestinal melanomas

Malignant melanoma is most often located in the skin and rarely found in the alimentary tract, and malignant gastrointestinal melanomas are usually metastatic. Primary gastrointestinal melanomas (PGIMs) occur at a frequency of 0.5 to 1 case per million, depending on race and latitude. Primary gastric melanomas (PGM) account for 12.7% of all PGIMs.

A 66-year-old woman with a previous history of chronic gastritis, kidney stones and coronary heart disease was diagnosed recently with anaemia and weight loss. She had previously undergone implantation of a cardiac pacemaker, implantation of a biological valve in the aorta and excision of her gallbladder.

Upon endoscopic evaluation, doctors found a stomach tumour that was approximately 5 cm in diameter. Histopathological examination of the tumour samples suggested the diagnosis of malignant melanoma [IHC: CK (−), CHR (−), SYN (−), HER2 (−), VIM (+), HMB45 (+)]. Due to insufficient availability of tissues, doctors again performed endoscopy procedure to take more samples. The samples revealed that the tumour was composed of epithelioid cells that lacked cohesive features, had abundant cytoplasm and had nuclei containing vacuoles and large nucleoli. The tumour cells were positive for Melan A expression and negative for CK AE1/AE3 expressions. Thus confirming the diagnosis of malignant melanoma. To exclude the presence of melanoma outside the gastrointestinal tract, dermatological and ophthalmological consultations, as well as imaging examinations were performed. The doctors observed stomach corpus tumour without infiltration of adjacent organs or enlarged lymph nodes in abdominal CT. They found no other nodular changes in the alimentary canal and metastasis in the lung.

Surgical treatment involved resection of the stomach, spleen and greater omentum and D2 lymphadenectomy with additional excision of the lymph nodes of the liver cavity. Surgeons anastomosed esophagus with the jejunum end to end with mechanical sutures (stapler EEA 25) on the Roux-en-Y loop.

Postoperative histopathological examination revealed tumour infiltration of the mucus membrane in the anterior wall of the stomach. Based on the histopathology and immunohistochemistry, the doctors diagnosed malignant melanoma. However, they didn't find any features suggesting angioinvasion or neuroinvasion. They observed a melanoma metastasis in one lymph node of the greater curvature. They also observed surgical margins, greater omentum and spleen were free from melanoma infiltration with no post-op complications. After the oncological consultation, doctors suggested the patient for chemotherapy. As the patient was not willing to give consent, further treatment was not pursued.

The doctors observed, no recurrence of the disease 18 months post-surgery. It has been demonstrated that the survival times for patients who undergo surgery compared to those who do not are 12 months and 2 months, respectively. The use of adjuvant chemotherapy may improve the results of treatment, whereas radiotherapy may be considered a method of palliative treatment.

For further information:

https://link.springer.com/article/10.1007/s12262-019-01988-z