Malignant melanoma: An important differential diagnosis for clear cell sarcoma of the gastrointestinal tract

Table 1 Comparison of characteristics of gastrointestinal clear cell sarcoma and gastrointestinal malignant melanoma

Tumor	Tissue origin	Imaging examination	Gross appearance	Histopathological examination	Immunohistochemistry	Molecular genetic testing	Diagnosis	Treatment	Prognosis
Clear cell sarcoma	Neural crest[21]	Hypodense mass	Grayish white, hard, ovoid	The nuclei of the tumor cells were round, uniform in size, with clear cytoplasm, scattered osteoclastic multinucleated giant cells were seen, and intracellular melanin was uncommon[23]	Most cases were positive for HMB-45, Melan-A, S-100, MiTF, PNL-2, and waveform protein, and in some cases melanin and/or melanosomes were present[26,27]	There are no BRAF or NRAS gene mutations, and most cases have the t(12;22)(q13;q12) translocation [29], which results in the EWS-ATF1 fusion gene[30]	Confirming the diagnosis relies on molecular biology	There is no consensus on a systemic treatment approach, and surgery remains the standard of care	High rate of recurrence or metastasis and poor prognosis
Malignant melanoma	Neural crest[22]	Low density occupying lesion	Grayish black, ill-defined, with infiltrative growths	The histomorphology is complex and variable, nuclear schizophrenia is common, osteoblast-like multinucleated giant cells are rare, and in most cases the tumor cells contain melanin granules that are brownish-yellow or black in color[24,25]	The rate of positivity for HMB-45, S-100, and vimentin was more than 90%, and Melan-A and PNL-2 were expressed to varying degrees[28]	Presence of BRAF gene mutations, absence of t(12;22)(q13;q12) chromosomal translocation and EWSR1 gene rearrangement[31,32]	Histopathologic examination is the gold standard for diagnosis	Comprehensive treatment including surgery, radiation, and chemotherapy	Highly malignant, highly invasive, and highly metastatic with poor clinical prognosis