Rare Encounter: A Study of Oral Cavity Kaposi Sarcoma in Two Cases

Abstract Introduction/Objective Kaposi Sarcoma (KS) of the oral cavity, is an unusual vascular endothelial neoplasm and is the most common malignancy affecting the skin and internal organs in patients with AIDS. The tumor is caused by Human herpesvirus 8 (HHV-8). It rarely metastasizes and can be treated and totally cured by treating the AIDS disease. The oral cavity may be the only/ first site of KS, and therefore, is important in the diagnosis. The lesions present as multiple red-purple macules that develop into plaques or nodules. The hallmark microscopic features are spindle cell proliferation and irregular small, vascular slits, which often run parallel to the epithelium, as well as extravasated RBCs, with hemosiderin deposition and hyaline globules in 50% of lesions. HHV-8 nuclear staining is positive in all cases, which is crucial to differentiate it from other conditions with positivity for spindled cell markers: CD34, CD31, ERG, and FVIII R. The tumor can also be positive for lymphatic-specific markers (D2-40, LYVE-1, VEGFR3, and PROX1) Methods/Case Report We reviewed retrospectively archived cases from our TUH oral pathology database with available H&E slides diagnosed for Kaposi sarcoma between 2013 – 2023. We retrieved two confirmed cases, and we reviewed the slides and clinical information. Results (if a Case Study enter NA) Data were colleceted and analysed. Conclusion Incorporating Kaposi sarcoma into the differential diagnosis of pigmented red-purple vascular lesions in the oral cavity is of paramount importance. Detection of Kaposi sarcoma in this region bears significant prognostic implications, often serving as an initial sign of Kaposi sarcoma and indicating HIV infection. Lesions typically localize on the palate and gingiva. Heightened awareness of this clinical entity is crucial for facilitating early detection and treatment with antiretroviral drugs. Furthermore, the differential diagnosis for lesions with similar clinical presentations encompasses a broad spectrum, including benign conditions such as pyogenic granuloma, hemangioma, bacillary angiomatosis, and even granulation issue, as well as malignant tumors like angiosarcoma. It is noteworthy that considering Kaposi sarcoma in this context prompts pathologists to prioritize ordering stains for HHV-8. This diagnostic approach is supported by the exceptional sensitivity and specificity of HHV-8 stains, which exhibit 99% sensitivity and 100% specificity for diagnosing Kaposi sarcoma, while consistently yielding negative results in all other entities within the differential diagnosis.