Mesenchymal-to-endothelial transition in Kaposi sarcoma: a histogenetic hypothesis based on a case series and literature review.

ObjectivesAlthough several studies have been conducted regarding Kaposi sarcoma (KS), its histogenesis still remains to be elucidated. The aim of our study was to analyze the immunophenotype of Kaposi sarcoma and to present a hypothesis about the histogenesis of this tumor, based on a case series and a review of relevant literature.MethodsIn 15 cases of KSs diagnosed during 2000-2011, the clinicopathological features were correlated with the immunoexpression of c-Kit, SMA, CD34, CD31, vascular endothelial growth factor (VEGF), COX-2, c-KIT, smooth muscle antigen (SMA), and stem cell surface marker CD105.ResultsBoth CD105 and c-KIT rate of the spindle-shaped tumor cell positivity increased in parallel to the pathological stage. All cases displayed CD105 and weak c-KIT positivity in the endothelial cells. SMA, VEGF, and COX-2 were focally expressed in all cases. CD34 marked both endothelium and spindle-shaped tumor cells. No c-KIT expression was noticed in KS of the internal organs.ConclusionsKS seems to be a variant of myofibroblastic tumors that originates from the viral modified pluripotent mesenchymal cells of the connective tissue transformed in spindle-shaped KS cells, followed by a mesenchymal-endothelial transition and a myofibroblastic-like differentiation. This paper mailnly showed that KS cannot be considered a pure vascular tumor

Immunohistochemical features of a plaque-stage Kaposi sarcoma diagnosed in a 75-year old male that presented a nodule on the sole (case 7).

<p>A- Diffuse expression of CD34; B - Endothelial positivity of CD105; C - Focal expression of c-KIT; D - Focal expression of SMA.</p

Immunohistochemical particularities of a nodular-stage Kaposi sarcoma diagnosed in a 53-year old male that presented a nodule on the thigh (case 3).

<p>A - Diffuse expression of COX-2; B – VEGF is diffusely expressed in the spindle-shaped tumor cells with focally slit-like leaky pseudovascular spaces; C - CD34 marks both endothelial cells (e) and the perivascular tumor cells (p) but the middle vascular layer (m) was negative; D - SMA expression can be seen in the middle vascular layer and the perivascular tumor cells.</p

Clinicopathological and immunohistochemical features of patients with Kaposi sarcoma (F = female; M = male; V = vessels; T = tumor cells; ± referes to focal positivity and + represents diffuse expression).

<p>Clinicopathological and immunohistochemical features of patients with Kaposi sarcoma (F = female; M = male; V = vessels; T = tumor cells; ± referes to focal positivity and + represents diffuse expression).</p

Immunohistochemical features of a nodular-stage Kaposi sarcoma diagnosed in a 65-year old male that presented a nodule on the sole (case 1).

<p>A- Diffuse expression of CD34; B – Diffuse expression of CD105 in the endothelial cells and spindle-shaped tumor cells; C - Diffuse expression of c-KIT in the spindle-shaped tumor-cells without endothelial positivity; D - Focal expression of SMA.</p