Undifferentiated sinonasal malignant melanoma: A case report

Abstract

Undifferentiated sinonasal malignant melanoma (MM) is a rare type of tumor, which can be easily misdiagnosed. The present study reports a 41-year-old male patient who presented with a 4-day history of epistaxis. Clinical examination and radiological imaging lead to the detection of a mass in the right sinonasal region. Histopathological examination revealed that the mass was composed of malignant epithelioid cells arranged in nests and sheets. These cells displayed a hemangiopericytoma-like pattern with antler-like branching vessels. Immunohistochemical staining revealed that the tumor cells exhibited negative expression of melanocytic markers. This increased the difficulty of distinguishing undifferentiated MM from other malignant tumors located in the sinonasal area, particularly undifferentiated nasopharyngeal carcinoma. The diagnosis of undifferentiated MM was determined by ultrastructures, including the mature melanosomes and premelanosomes, in tumor cells by transmission electron microscopy. The present study suggests that the analysis of cancer stem cell marker and vasculogenic mimicry may be an important auxiliary tool for the diagnosis of MM.

Metastatic Undifferentiated Melanoma Mimicking a Primary Bone Tumor: A Potential Diagnostic Pitfall

“…The diagnosis required transmission electron microscopy analysis, revealing the presence of mature melanosomes and premelanosomes in the tumor cells. 20 This case differs from ours and those in existing reports of sinonasal melanoma in which the primary tumor retained strong expression of classic melanocytic markers. 20,21 In summary, we report a very rare case of UM transforming and metastasizing from a primary sinonasal melanoma in which the former displayed OLGCs mimicking a primary bone tumor.…”

“…20 This case differs from ours and those in existing reports of sinonasal melanoma in which the primary tumor retained strong expression of classic melanocytic markers. 20,21 In summary, we report a very rare case of UM transforming and metastasizing from a primary sinonasal melanoma in which the former displayed OLGCs mimicking a primary bone tumor. Importantly, the mutation identified in the original primary tumor, a Q61H mutation in codon 61 of the KRAS gene, was retained in the UM even in the setting of loss of typical melanocytic markers.…”

“…The diagnosis required transmission electron microscopy analysis, revealing the presence of mature melanosomes and premelanosomes in the tumor cells. 20 This case differs from ours and those in existing reports of sinonasal melanoma in which the primary tumor retained strong expression of classic melanocytic markers. 20,21…”

“…There is only 1 published case of primary sinonasal malignant melanoma with undifferentiated features. 20 The authors reported a 41-year-old man from China with a primary dedifferentiated sinonasal melanoma mimicking a poorly differentiated carcinoma, expressing epithelial markers (ie, EMA, pancytokeratin) in the absence of HMB-45, Melan-A, S100, and SOX10 expression. The diagnosis required transmission electron microscopy analysis, revealing the presence of mature melanosomes and premelanosomes in the tumor cells.…”

Immunohistochemical and Molecular Features of Melanomas Exhibiting Intratumor and Intertumor Histomorphologic Heterogeneity

“…Alternatively, the detection of overlapping mutations demonstrated in our current study may help pathologists accurately diagnose primary melanoma in cases with unusual histophenotypic presentations which may lead to a misdiagnosis of dedifferentiated or collision tumor, and may be useful in the diagnosis of histomorphologically heterogeneous metastases mimicking carcinoma or unclassified sarcoma [12]. Also, loss or gain of genetic alterations present only in metastatic lesions may reveal therapeutically actionable targets that can significantly impact the clinical management of patients with melanoma refractory to conventional therapy [13,14,15,16,17,18].…”