THE DIAGNOSIS C. Primary Intraoral Melanoma
Higher power magnification of the papillary mass shows irregularly-shaped, large, darkly-staining cells scattered throughout the epithelium. These cellular changes are indicators of possible malignancy. Some of the basal cells show faint localized pigmentation. The scattering of the individual large cells is called“ pagetoid” spread and appears in several pathologic conditions( Fig. 4). Given this presentation, it did not appear to simply be a papilloma, so additional immunohistochemical stains were ordered. S100, SOX10, and melan-A immunohistochemical stains were positive in the malignant cells( Fig. 5). PRAME was negative and cytokeratin AE1 / 3 was negative in malignant cells but positive in epithelial cells. This pattern of staining and the histopathological presentation supports the diagnosis of intraoral melanoma. The patient subsequently denied any history of cutaneous melanoma. In the absence of a known primary elsewhere in the body, we considered this to be a primary intraoral melanoma. The patient was referred for further evaluation and management.
Primary intraoral melanoma is a rare, high-grade malignancy arising from the transformation of melanocytes, which are neuroectodermal cells that are responsible for producing melanin. [ 1 ] These tumors account for approximately 1 % of all melanomas and only 0.5 % of all intraoral malignancies. [ 2 ] Intraoral melanomas are reported across a broad age range from 20 to 80 years of age, with a male predilection.[ 2 ]
Oral melanomas with a papillary architecture are exceedingly rare but have been documented in literature. [ 3, 4 ] One reported case of papillary melanoma of the oral cavity was a known metastasis. [ 3 ] However, this morphology is most frequently seen in sinonasal melanomas. [ 4 ] Oral melanomas often remain asymptomatic until advanced stages and have a poor prognosis, making early diagnosis critical. [ 3 ] Due to its diverse clinical and histopathologic manifestations, oral melanoma can mimic other entities, complicating diagnosis. Additionally, this lesion breaks most of the“ ABCDE” rules of melanoma in that the lesion was not Asymmetric, it did not have an irregular Border, and it was not multi-Colored. In support of a melanoma diagnosis, its Diameter was greater than 6mm, and it had Evolved over a short time. In such a case, a detailed medical history to rule out metastasis and a full immunohistochemical work-up is essential for a definitive and accurate diagnosis. The patient subsequently underwent an infrastructure maxillectomy for residual melanoma. No perineural, lymphovascular, or bone invasion was noted, and all submitted lymph nodes were negative for tumor.
Figure 4
Confluent nests of malignant cells within the connective tissue invading the superficial epithelium( pagetoid spread). Rare pigmentation is indicated by the arrow( H & E, 200x).
Figure 5
Melan-A immunohistochemical stain highlighting the cytoplasm of the malignant cells, confirming a melanocytic lineage( 100x).
30 MAY / JUNE 2025 | PENNSYLVANIA DENTAL JOURNAL