Current and Future Tools for Diagnosis of Kaposi's Sarcoma

Abstract

Kaposi's sarcoma (KS) is a rare, atypical malignancy associated with immunosuppression and can be qualified as an opportunistic tumor, which responds to immune modulation or restoration. Four different epidemiological forms have been individualized (AIDS-related, iatrogenic, endemic or classic KS). Although clinical examination is sufficient to diagnose cutaneous lesions of KS, additional explorations are necessary in order to detect lesions involving other organs. New histological markers have been developed in recent years concerning the detection of HHV-8 latent or lytic proteins in the lesions, helping to confirm the diagnosis when it is clinically doubtful. More recently, the evaluation of the local immune response has also been shown to provide some guidance in choosing the appropriate therapeutic option when necessary. We also review the indication and the results of conventional radiological imaging and of non-invasive imaging tools such as ¹⁸F-fluoro-deoxy-glucose positron emission tomography, thermography and laser Doppler imaging for the diagnosis of KS and for the follow-up of therapeutic response in patients requiring systemic treatment.

Keywords: FDG-PET; Kaposi’s sarcoma; diagnostic; non-invasive imaging tools; staging.

Figure 1

Examples of KS clinical lesions. (A) red and pink papules in a patient with classic KS (early stage). (B) nodular lesions on the foot in a patient with a more agressive form of classic KS. (C) violin macule and nodule of the palate in a patient with AIDS-KS. (D) voluminous ulcerative tumor in a patient with an anaplastic form of endemic KS.

Figure 2

Histopathology of Kaposi sarcoma (KS). (A) Patch-stage KS showing dissection of dermal collagen by ectatic vascular spaces (H&E, ×50). (B) Small native vessels protrude into abnormal vascular spaces forming the promontory sign, admixed with lymphocytes and plasma cells (H&E, ×200). (C,D) Nodular-stage KS showing fascicles of spindled cells with slit-like vascular channels containing erythrocytes (H&E ×20 and ×200). (E) The spindled tumor cells are positive for ERG (ERG antibody, ×200) (F) Tumor cell nuclei demonstrate immunoreactivity for HHV-8 (LNA-1 antibody, ×200).

Figure 3

Pulmonary involvement in a 47-year-old male with AIDS-KS. Chest radiography (A) shows perihilar infiltrates in the mid and lower lung zones. Chest CT shows bilateral linear and nodular peribronchovascular interstitial thickening with symmetrical distribution in axial (B) and coronal planes (C) associated with ill-defined nodules (arrows) and interlobular septal thickening.

Figure 4

Thoracic involvement in KS. (A) Highly abundant right pleural effusion and low abundance left pleural effusion with peribronchovascular thickening (arrow). (B) Nodule with halo sign in the left superior lung (arrow). (C) Bilateral pleural effusion on contrast-enhanced CT-scan. (D) Interlobular septal thickening (arrow) in a secondary pulmonary lobule of middle and lower lungs.

Figure 5

A 27-year-old man, three months after renal transplant. Chest CT-scan showing (A) bilateral pleural effusion, peribronchovascular thickening in the lower lungs (arrow) with irregular narrowing of the bronchial lumen. Contrast-enhanced abdominal CT showing in axial (B) and coronal (C) planes soft-tissue infiltration (arrows) of pancreatic and retroperitoneal lymphadenopathy (arrows) due to pathologically proven KS.

Figure 6

A 29-year-old man with cutaneous, hepatosplenic and lymph nodes involvement in KS. (A) Coronal plane contrast-enhanced abdominal CT showing hepato-splenomegaly as well as cutaneous and subcutaneous nodules (arrow). Contrast-enhanced chest CT showing enlarged subcarinal lymph nodes ((B), arow), irregularity of the pleural surface ((B), asterisk) and abnormally enlarged lymph nodes in the retroperitoneum ((C), arrow) due to histologically confirmed KS.

Figure 7

Head CT in a 34-old-year man. It shows lytic left parietal lesion in axial (A) and sagittal (B) planes and a left vertebral osteolytic cervical lesion (C3) in the axial plane ((C), arrow).

Figure 8

Foot CT-scan (A) and MRI (B–D) of a 38-year-old man with AIDS-KS. Coronal plane CT (A) showing multiple osteolytic lesions (arrows), with MRI showing hypo-intensity on T1-weighted images ((B), white arrows), hyper-intensity on T2 weighted images ((C), white arrows) and important soft tissue signal enhancement after gadolinium injection ((D), black arrows) in sagittal slices.

Figure 9

Examples of positive FDG-PET in three patients with KS. (A) Maximal intensity projection (MIP) PET and axial plane PET/CT fusion images in a 20-year-old male with iatrogenic immunosuppressive KS (liver transplant) showing involvement of palatine tonsils, cervical and abdominal lymph nodes and the spleen. (B) MIP PET and axial plane PET/CT fusion images in a 57-year-old male with endemic KS showing involvement in the right adrenal gland, both feet (skin and subcutaneous involvement) and possibly of the right thigh muscles (not histologically confirmed). (C) MIP PET and axial plane PET, CT and PET/CT fusion images in a 58-year-old male with iatrogenic immunosuppressive KS (heart transplant) showing diffuse nodular lung involvement.