From the Guidelines
Diagnosis of Kaposi's sarcoma requires a combination of clinical examination and histopathological confirmation, with a skin biopsy and immunohistochemical staining for human herpesvirus 8 (HHV-8) latency-associated nuclear antigen being essential for a definitive diagnosis. The diagnostic process typically begins with identification of characteristic skin lesions, which appear as purple, red, or brown patches or nodules on the skin, mucous membranes, or internal organs. A thorough clinical examination is necessary to identify these lesions and to assess the extent of disease. According to the NCCN clinical practice guidelines in oncology, version 2.2019 1, management of AIDS-related Kaposi sarcoma depends on location and extent of disease, highlighting the importance of accurate diagnosis.
Key features of the diagnostic process include:
- Identification of characteristic skin lesions
- Skin biopsy of the suspected lesion to examine for typical histological features
- Immunohistochemical staining for HHV-8 latency-associated nuclear antigen
- Additional diagnostic workup, such as endoscopy, bronchoscopy, and imaging studies, to assess the extent of disease
- Measurement of CD4 count and HIV viral load in HIV-positive patients
- Classification of the type of Kaposi's sarcoma, as this impacts treatment decisions, with options including ART alone for limited cutaneous disease, or ART with clinical trial or systemic therapy for advanced disease 1.
Early diagnosis is crucial, as treatment approaches vary based on disease extent, type, and underlying conditions, and the goal of therapy is to reduce or reverse symptoms, mitigate end organ damage, and achieve long-term disease control. The use of glucocorticoids should be avoided in patients with active or prior Kaposi sarcoma, given the potential to cause significant flares or relapses 1. Overall, the survival of patients with AIDS-related Kaposi sarcoma has greatly improved, and long-term survival can be the goal for many patients 1.
From the Research
Diagnosis of Kaposi's Sarcoma
- The diagnosis of Kaposi's sarcoma (KS) is primarily based on clinical features and confirmation by histology with immunohistochemistry 2.
- Clinical examination is sufficient to diagnose cutaneous lesions of KS, but additional explorations are necessary to detect lesions involving other organs 3.
- New histological markers have been developed to detect HHV-8 latent or lytic proteins in the lesions, helping to confirm the diagnosis when it is clinically doubtful 3.
- The evaluation of the local immune response can also provide guidance in choosing the appropriate therapeutic option when necessary 3.
Diagnostic Tools
- Conventional radiological imaging and non-invasive imaging tools such as 18F-fluoro-deoxy-glucose positron emission tomography, thermography, and laser Doppler imaging can be used for the diagnosis of KS and for the follow-up of therapeutic response in patients requiring systemic treatment 3.
- Histopathological and immunohistochemical analyses are essential for the diagnosis of KS 4.
- HHV-8 immunohistochemically biopsy-proven diagnosis of KS should be the gold standard 5.
Challenges in Diagnosis
- KS can masquerade as other entities, delaying prompt diagnosis 6.
- A high index of suspicion is required to diagnose ocular KS as these lesions can be mistaken for alternative entities 6.
- Clinical and histological discordance rates can be high, emphasizing the need for biopsy and HHV-8 LAN-1 immunophenotyping for all clinical lesions suspicious of KS 5.