BULLOUS LESIONS IN KAPOSIS-SARCOMA - CASE-REPORT

Bullous lesions have been only rarely described in Kaposi's sarcoma (K S), and their histopathologic features have never been described in de tail. We report a case of bullous lesions of KS in an 82-year-old Ital ian woman. The patient had typical smooth pale reddish-grey slightly-r aised KS plaques on the legs, present for at least 10 years. Several d ull grayish-pink blisters (0.5 to 2 cm in diameter) affected both dors a of her feet and ankles symmetrically. Two punch biopsies were taken, one from an infiltrated KS plaque on the right buttock and the other from a bullous lesion on the right foot. Histopathologically, the late KS plaque on the buttock showed typical features of KS, with an incre ased number of spindle cells arranged in short bundles and extravasati on of erythrocytes. The bullous lesion on the foot showed a full-thick ness vascular neoplasm involving the upper and lower dermis and the su bcutaneous fat. The upper portion of the lesion contained many newly f ormed, highly-dilated blood vessels, touching the overlying epidermis and separated from it by a narrow band of collagen and endothelial cel ls; wide, empty spaces characterized the superficial dermis, in which preexisting venules and bands of collagen associated with nonatypical endothelial cells floated. All these findings would suggest a lymphang iomatous lesion, if the presence of specific diagnostic criteria of KS were not recognizable at a deeper level of the lesion. Various criter ia actually suggest that the bullous lesion may be regarded as an epip henomenon of a KS plaque lesion: (a) full-thickness involvement of the reticular dermis and, in this case, also of the subcutaneous fat; (b) dense and patchy lymphoplasmocytic infiltrate typical of plaque lesio ns and, much less frequently, of patch lesions; (c) presence of ectati c blood vessels, filled with plasma and erythrocytes (pseudoangiomatou s findings), a nonpathognomonic but highly characteristic finding of t he plaque lesion; and (d) as in the KS plaque lesions, in the bullous lesion as well the reticular dermis was characterized by an increased number of anastomosing bizarrely shaped vascular spaces lined by nonat ypical endothelial cells. We hypothesize that the prevalence of lympha ngiomatous differentiation in the upper dermis represents one of the m any features of KS lesions. When present, it may correlate with the cl inical feature of a blister.