Detection of KSHV in transbronchial biopsies in patients with Kaposi sarcoma

In transbronchial biopsies, Kaposi sarcoma (KS) is difficult to correctly diagnose by H&E staining due to the inherent vascular nature of the lung tissue, coupled with the subtle nature of the changes in early KS. Since KS-associated herpesvirus (KSHV) has been found in all clinical forms of KS, the detection of KSHV genomic DNA sequences and/or viral products may be helpful in the diagnosis of pulmonary KS. From their files during the past 10 years, the authors identified ten HIV/AIDS patients who were positive for KS in transbronchial biopsies and four HIV/AIDS patients with KS-negative transbronchial biopsies. Immunohistochemistry with antibodies against the latency-associated nuclear antigen (LANA-1 or LNA) of KSHV was performed. Nested polymerase chain reactions (PCR) with KSHV ORF-K1 or -K9 were performed in all cases, and the KSHV sequences were detected in 9/10 (90%) KS cases. Immunohistochemical analysis was able to detect 4/10 (40%) cases. One case was negative by both PCR and immunohistochemistry. Of the five KS cases that were not diagnosed definitively ("consistent with" or "suspicious for"), two were confirmed by both immunoreactivity and PCR. One of the negative control cases was positive for KSHV by PCR but not by immunohistochemistry. The patient was thereafter found to have a clinical history of pulmonary KS at another hospital. In conclusion, in transbronchial biopsies of the lung suspicious for KS, PCR is the most sensitive technique available for clinical diagnosis of KS. Immunohistochemistry analysis might be helpful in difficult pulmonary KS cases.