Diagnosis of Kaposi Sarcoma by a Modified Fine Needle Aspiration Method Combining Cell Block in Chinese Patients with Human Immunodeficiency Virus/Acquired Immunodeficiency Syndrome
Kaposi’s sarcoma (KS) is a low-grade vascular tumor that is among the most common neoplasms reported in patients with acquired immunodeficiency syndrome (AIDS). The disease is characterized by the development of dark or brown macules, plaques, or nodules on the skin and mucous membranes, which may bleed or ulcerate. In advanced stages, KS can also involve lymph nodes and visceral organs. Four types of KS have been identified based on epidemiological and clinical characteristics: classic KS, endemic KS (prevalent in equatorial Africa), AIDS-associated KS (AIDS-KS), and iatrogenic KS. The diagnosis of KS is critical for timely intervention, particularly in immunocompromised patients such as those with HIV/AIDS.
Fine needle aspiration cytology (FNAC) is a widely used diagnostic technique for evaluating lesions in organs such as the breast, thyroid gland, skin, and superficial lumps, as well as enlarged lymph nodes. FNAC is favored for its simplicity, cost-effectiveness, minimal invasiveness, safety, and rapid results with high diagnostic accuracy. Despite its advantages, there is limited literature on the use of FNAC combined with cell block preparation for diagnosing KS. This study evaluated the efficacy of this modified FNAC method in diagnosing KS among Chinese patients with HIV/AIDS.
The study enrolled 771 HIV-infected patients with lymphadenopathy or superficial lumps who were admitted to the Department of Pathology at Beijing Ditan Hospital, Capital Medical University, between June 2009 and February 2019. FNAC was performed on all patients after obtaining informed consent. The procedure was carried out without anesthesia using an auto-vacuumed syringe, which facilitated the collection of sufficient material for both smears and cell block preparation. The aspirated material was flushed onto slides to create thin smears, which were immediately fixed with 95% ethyl alcohol and stained with Hematoxylin and Eosin (H&E) for cytological examination. The remaining material was processed into cell blocks using ethanol coagulation and formaldehyde fixation. The cell blocks were treated similarly to surgical biopsy specimens, including formalin fixation, paraffin embedding, and sectioning at 4 to 5 mm thickness, followed by H&E staining and immunohistochemical staining.
Immunohistochemical analyses were performed using the avidin-biotin-peroxidase method with the Leica Autostaining System. The following antibodies were used: CD31, CD34, factor VIII, HHV-8, smooth muscle actin (SMA), Desmin, S-100, Vimentin, and Cytokeratin (CK AE1/AE3). CD4+ T cell counts were determined using flow cytometry. The study adhered to ethical standards and was approved by the Ethics Committee of Beijing Ditan Hospital.
Of the 771 patients, 16 (2.1%) were diagnosed with KS. All KS patients were male, with an average age of 37.3 ± 10.6 years. The distribution of KS lesions included lymph nodes (8 cases: 4 cervical, 3 inguinal, and 1 posterior), oral mucosa (3 cases), and subcutaneous nodules (5 cases). The average age of patients with lymph node involvement (29.5 ± 4.8 years) was significantly lower than that of patients with subcutaneous nodules or oral mucosa involvement (P = 0.002 and <0.001, respectively). The average CD4+ T cell count for all KS patients was 83.9 ± 58.2/mL, with no correlation between CD4+ T cell count and age or lesion site.
Cytological examination of the smears revealed hypercellular features with plump spindle cells in a hemorrhagic background. The cells exhibited a moderate amount of eosinophilic cytoplasm, oval to spindle nuclei with mild pleomorphism, inconspicuous nucleoli, and finely granular chromatin. Few mitotic figures were observed, mimicking a low-grade spindle cell neoplasm. However, other histological features such as erythrocyte exosmosis and hemosiderin deposition were difficult to identify due to the hemorrhagic background.
The cell block sections provided a clearer view of the vasoformative architecture, characterized by proliferating blood vessels arranged in slit-like spaces and fascicles filled with red blood cells. These spaces were separated by spindled cells with moderate eosinophilic cytoplasm and mild to moderate nuclear atypia. Inflammatory cells, primarily lymphocytes, were observed at the tumor periphery. The morphological features of the cell blocks were similar to those seen in histopathology and were invaluable for definitive diagnosis.
Immunohistochemical staining revealed that the tumor cells were highly positive for CD31, CD34, factor VIII, Vimentin, and HHV-8. Negative results were obtained for SMA, Desmin, S-100, and CK AE1/AE3. Specifically, CD31 was expressed in 15 cases, CD34 in 16 cases, factor VIII in 13 cases, Vimentin in 16 cases, and HHV-8 in 14 cases. HHV-8 immunohistochemistry is particularly diagnostic for KS, as it is specific to the disease and is detected in the nuclei of KS spindle cells.
The study confirmed that KS is more prevalent in males, with all diagnosed patients being male. This aligns with previous studies reporting a male-to-female ratio of approximately 10:1 to 15:1. Lymph node involvement was more common in younger patients, with an average age of 29.5 ± 4.8 years, reflecting the higher prevalence of HIV in individuals aged 20 to 40 years. The lower extremities were the most common site for skin lesions, accounting for 60% of cases. Oral involvement, observed in 18.8% of cases, is highly indicative of AIDS-related KS.
Surgical biopsy remains the gold standard for KS diagnosis but is often costly, time-consuming, and associated with complications. FNAC, particularly when combined with cell block preparation, offers a viable alternative. The modified FNAC method used in this study, which employs an auto-vacuumed syringe, ensures the collection of sufficient material for both smears and cell blocks. This approach allows for cytomorphological, morphological, and immunohistochemical evaluation, significantly enhancing diagnostic accuracy.
The diagnostic accuracy of FNAC has been reported to be as high as 98.9% in some studies, increasing to 100% when combined with cell block preparation. The success of FNAC largely depends on the experience of the pathologist, as an experienced practitioner can perform on-site adequacy assessments and repeat the procedure if necessary to obtain adequate material.
In conclusion, the study demonstrated that FNAC combined with cell block preparation is a reliable and effective method for diagnosing KS in patients with HIV/AIDS. The cytomorphological and immunohistochemical features of cell blocks provide high diagnostic accuracy, making this approach a valuable tool in the management of KS. The findings underscore the importance of integrating FNAC and cell block techniques in clinical practice, particularly in resource-limited settings where surgical biopsy may not be feasible.
doi.org/10.1097/CM9.0000000000001137
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