Primary Intraparotid Lymph Node Kaposi Sarcoma in an HIV-negative Patient with Chronic Hepatitis B Receiving Antiviral Therapy: A Rare Case Report

Technical Summary: Primary Intraparotid Lymph Node Kaposi Sarcoma in an HIV-Negative Patient with Chronic Hepatitis B

Problem Statement
Kaposi sarcoma (KS) is a vascular neoplasm driven by human herpesvirus-8 (HHV-8), typically manifesting in immunocompromised populations, particularly those with HIV infection. While KS can involve lymph nodes, primary involvement of an intraparotid lymph node is exceptionally rare, especially in HIV-negative individuals. Most documented cases of parotid KS represent secondary involvement in the context of disseminated HIV-associated disease. Furthermore, the coexistence of KS with chronic Hepatitis B virus (HBV) infection is an unestablished association, with no clear causal link defined in existing literature. This case addresses the diagnostic challenge of identifying an isolated intraparotid KS lesion in a patient without classic risk factors (HIV, immunosuppression) and explores the clinical implications of concurrent chronic HBV infection under antiviral therapy.

Methodology
The study presents a single-case report of a 58-year-old HIV-negative male with well-controlled chronic hepatitis B (on antiviral therapy with tenofovir) presenting with a painless, slowly enlarging right parotid mass.

• Diagnostic Imaging: Contrast-enhanced computed tomography (CT) identified a well-defined, enhancing lesion (21 mm) in the superficial lobe of the right parotid gland.
• Biopsy and Surgical Intervention: An initial ultrasound-guided core biopsy was non-diagnostic, yielding only nonspecific fibrovascular tissue. Consequently, the patient underwent a right superficial partial parotidectomy with retrograde identification and preservation of the facial nerve branches.
• Pathological Analysis: The excised specimen underwent histological examination and immunohistochemical staining. Key markers included CD31, HHV-8, ERG, TLE1, S100, cytokeratin (CK), smooth muscle actin (SMA), and Desmin. A Ki-67 proliferation index was also calculated.
• Staging and Follow-up: Post-operative whole-body PET/CT was performed to rule out systemic disease. The patient was followed for 19 months to monitor for recurrence.

Key Results

• Histopathology: Microscopic analysis revealed a tumor originating within an intraparotid lymph node rather than the salivary parenchyma. The lesion featured angiomatoid, slit-like vascular spaces containing red blood cells, surrounded by spindle cells in intersecting fascicles.
• Immunohistochemistry: The tumor cells were positive for endothelial markers (CD31, ERG), HHV-8 (confirming KS), and TLE1. The Ki-67 proliferation index was 50%. The cells were negative for S100, CK, SMA, and Desmin, ruling out other spindle-cell neoplasms and carcinomas.
• Clinical Outcome: The surgical margins were negative. Post-operative PET/CT scans on two separate occasions showed no evidence of residual tumor or systemic dissemination. The patient remained disease-free after 19 months of follow-up without adjuvant chemotherapy or radiotherapy.
• Comparative Analysis: A review of previous literature indicates that while parotid KS has been reported in HIV-negative patients (e.g., Puterman et al., 1983; Pagani et al., 2009), the combination of an isolated intraparotid lymph node lesion, HIV-negative status, and concurrent chronic HBV infection under antiviral suppression has not been previously documented.

Key Contributions

• Rare Presentation: This report documents an exceptionally rare instance of primary Kaposi sarcoma arising specifically within an intraparotid lymph node in an HIV-negative, immunocompetent patient.
• Diagnostic Clarification: The case underscores the limitations of non-invasive imaging and core biopsy in diagnosing parotid KS, noting that imaging often mimics benign salivary tumors (e.g., pleomorphic adenoma) and biopsies may yield inconclusive results due to the heterogeneous architecture of KS. It reinforces the necessity of complete surgical excision for definitive diagnosis when suspicion persists.
• Management Strategy: The study supports the efficacy of surgical excision alone for localized, primary parotid KS in HIV-negative patients, avoiding the need for systemic chemotherapy or radiotherapy when negative margins and no systemic disease are confirmed.
• HBV Association: While the authors do not establish a causal link, the report highlights the coexistence of chronic HBV (controlled by antivirals) and KS, suggesting this association warrants further investigation in larger studies, though it may currently be considered incidental.

Significance and Claims
The paper claims to present the first reported case of isolated intraparotid lymph node KS in an HIV-negative patient with chronic HBV receiving antiviral therapy. The authors assert that this case expands the limited literature on atypical KS presentations, demonstrating that KS should remain a differential diagnosis for atypical parotid masses even in the absence of HIV infection or disseminated disease. The significance lies in broadening the clinical spectrum of KS to include localized, isolated lymph node lesions in immunocompetent hosts, thereby facilitating earlier diagnosis and appropriate surgical management while avoiding unnecessary systemic treatments. The authors maintain a modest stance, acknowledging that the rarity of the case limits broad generalizations and that the relationship between chronic HBV and KS pathogenesis remains speculative and requires further multicenter investigation.