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New pitfalls in the diagnosis of Kaposi sarcoma

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By Warren R. Heymann, MD
June 16, 2016

Human Herpes Virus-8 (HHV-8) is the common denominator in all forms of Kaposi sarcoma (KS) — classic, endemic, post-transplant/immunosuppressive, and epidemic/HIV. Virtually all cases will demonstrate HHV-8 by immunohistochemistry in all types.

Manuraj et al present the instructive case of a 46 year-old HIV- positive man with characteristic lesions of KS, both clinically and histologically, with the exception that the immunohistochemistry (IHC) for HHV-8 latent nuclear antigen was repeatedly negative.  The patient was treated with Atripla and had a very low viral load (<40 copies/ml).  Although in situ hybridization would have been an excellent alternative to determine the presence of HHV-8 in the samples, this was not available to the authors. They were able to document HHV-8 infection utilizing PCR on the paraffin blocks using primers for the ORF 26 gene. The authors surmised that negative immunohistochemistry for HHV-8 may be more common than this isolated report, especially for those with low HIV viral loads. This report highlights the fact that one cannot rely exclusively on the presence of HHV-8 positivity to secure a diagnosis of KS (1).

Clinicians and dermatopathologists also should be aware of the recently described “Pyogenic Granuloma-like Kaposi’s Sarcoma” (PGLKS). These lesions are seen in HIV-negative men older than 60 years. Lesions are solitary, acral, usually on the hands, and clinically look like polypoid, pedunculated pyogenic granulomas. Histologically they mimic PGs, however they stain positively for HHV-8 on IHC. As opposed to classical KS (which characteristically stains for lymphatics with D2-40) stains for D2-40 are negative in PGLKS. The authors surmise that these are early lesions of KS that have not yet maturely differentiated to demonstrate lymphatic differentiation. As there are few reports of PGLKS in the literature, it is difficult to know how to follow these patients. Future studies will help guide management.

As I remind our residents, when you see a PG in an adult, don’t just cauterize the lesion, biopsy it. Certainly you don’t want to misdiagnose an amelanotic melanoma. I don’t think you would want to miss a PGLKS either.

1. Manuraj S, et al. Negative HHV-8 immunoreactivity in HIV associated Kaposi’s sarcoma. J Cutan Pathol 2016; 43: 626-8.
2. Cabibi D, et al. D2-40 negative pyogenic granuloma-like Kaposi’s sarcoma: Diagnostic features and histogenic hypothesis of an uncommon skin tumor in HIV-negative patients. Pathol Res Pract 2015; 211: 528-32.

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