Differentials
Bacillary angiomatosis
SIGNS / SYMPTOMS
Due to infection by Bartonella henselae. Red papules or nodules that mimic KS may involve the skin, soft tissue, lymph nodes, and internal organs with or without associated HIV infection.
INVESTIGATIONS
Tissue biopsy shows lobules of capillaries with epithelioid endothelial cells, apoptotic neutrophils, and extracellular bacteria (silver stain). Lesional cells are negative for latency-associated nuclear antigen-1 (LANA-1) of HHV-8 using immunohistochemistry. Microbiology studies for Bartonella microorganisms may be helpful.
Pyogenic granuloma
SIGNS / SYMPTOMS
Rapidly growing polypoid red mass with an epidermal collarette, often seen on the finger or lips; is unrelated to HIV infection.
INVESTIGATIONS
Tissue biopsy shows a benign lobular capillary proliferation. Lesional cells are negative for latency-associated nuclear antigen-1 (LANA-1) of HHV-8 using immunohistochemistry.
Dermatofibroma
SIGNS / SYMPTOMS
A benign lesion most commonly involving the skin with similar appearance to the papulonodular form of KS. Varying degrees of hemorrhage and pigmentation may be seen.
INVESTIGATIONS
Tissue biopsy shows a benign proliferation of spindle-shaped cells, many of which are reminiscent of histiocytes, together with varying amounts of collagen. Hemorrhage may be present. Lesional cells are negative for latency-associated nuclear antigen-1 (LANA-1) of HHV-8 using immunohistochemistry.
Angioma
SIGNS / SYMPTOMS
Benign vascular lesions, with/without underlying HIV infection, may mimic KS.
INVESTIGATIONS
Tissue biopsy shows a benign vascular proliferation or malformation that is negative for latency-associated nuclear antigen-1 (LANA-1) of HHV-8 immunostaining.
Pigmented purpuric dermatoses
SIGNS / SYMPTOMS
Patients present with orange-brown speckled discoloration of the lower limbs (Schamberg disease) that is unrelated to HIV infection.
INVESTIGATIONS
Tissue biopsy is characterized by extravasation of erythrocytes in the skin with marked hemosiderin deposition. This may mimic KS in the regressive phase.[47]
Hemangioendothelioma
SIGNS / SYMPTOMS
Low-grade vascular neoplasm that may mimic KS, usually involving the distal extremities of young individuals. Unrelated to HHV-8 and/or HIV infection.
INVESTIGATIONS
Histopathology of the tissue biopsy shows a vascular tumor containing endothelial cells, which may be kaposiform in appearance, with prominent intracytoplasmic lumina. Lesional cells are negative for latency-associated nuclear antigen-1 (LANA-1) of HHV-8 using immunohistochemistry.
Angiosarcoma
SIGNS / SYMPTOMS
May be more aggressive than KS with frequent recurrences that involve extensive areas of face and scalp, regional lymph nodes, lungs, and other organs. Unrelated to HHV-8 and/or HIV infection.
INVESTIGATIONS
Tissue biopsy shows an infiltrating vascular neoplasm containing spindle-shaped to epithelioid endothelial cells with marked atypia. HHV-8 immunoreactivity is typically negative.
EBV-associated smooth muscle tumor
SIGNS / SYMPTOMS
Typically young, severely immunosuppressed patients present with multifocal benign (leiomyoma) and/or malignant (leiomyosarcoma) tumors. The most common site of involvement is the brain.[48]
INVESTIGATIONS
Tissue biopsy shows spindle tumor cells with a smooth muscle immunophenotype that are EBV infected (EBER positive).
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