Kaposi's sarcoma, classic and AIDS related 
Clinica/ and /aboratory study 
CLASSIC AND AIDS-RELATED KAPOSI'S SARCOMA 
AN ULTRASTRUCTURAL INVESTIGATION 
L. Celleno, A. Mastroianni, M. G. Borgia, F. Cottoni and D. Cerimele 
ABSTRACT 
Electron microscopy was used to study lesional biopsy specimens from 25 patients with Kaposi's sarcoma (20 with the 
classical form and 5 associated with AIDS). The study revealed that the AIDS-associated lesions were characterized by more 
rapidly developing damage to the capillary endothelium with respect to the classical lesions; tubuloreticular structures were 
also found more often within the cells of the former lesions. 
Our ultrastructural findings suggest that the endothelial cells of the affected blood vessels may be responsible for the 
histogenesis of the disease. In this study we were not able to demonstrate the presence of vira! particles within the cells of the 
classical lesions. Virus-like particles were observed within the AIDS-associated lesions, but there was no sign of vira! 
replication. 
KEYWORDS 
Kaposi's sarcoma, AIDS, ultrastructural findings 
INTRODUCTION 
Kaposi's sarcoma is a multilesional, vascular neoplasm 
which generally evolves slowly. Three main types have been 
distinguished on the basis of clinical, epidemiological and 
evolutionary features: the classical or sporadic form, the 
endemic, and the epidemic form that is associated with the 
acta dermatovenero/ogica AP A. Vol 2, 93, No 3 
Acquired Immunodeficiency Sindrome (AIDS) (1 , 2, 3, 4). 
Histologically Kaposi's sarcoma is characterized by new ly 
formed, angular or irregularly shaped vessels that often 
appear around the venules. In some cases the nuclei of the . 
cells that make up these vessels are thin and spindle-shaped. 
71 
Kaposi's sarcoma, classic and AIDS relared 
As the disease progresses these irregular vessels increase in 
nurnber, and scattered spindle-shaped cells become visible 
(41). Extravasated erythrocytes can be observed among 
collagen bundles. In advancedKaposi's sarcoma these spindle-
shaped cells are organized into bundles. Extravasated 
erythrocytes can still be seen occasionally, while perivascular 
infiltrates containing lymphocytes and plasmacells are 
common (5). 
The etiology and pathogenesis ofKaposi's sarcoma are still 
being debated in spite of nurnerous studies that have been 
carried out on the ultrastructure of this neoplasm (6-12, 14, 
17, 18, 20). 
Recent interest in this disease has stemmed from its 
association with AIDS, and the majority of ultrastructural 
studies conducted thus far have concentrated on this form 
(10-12), although some groups have attempted to compare 
the ultrastructural features of the epidernic and sporadic 
forms (13, 18, 19). 
Ultrastructural findings indicate that this singular 
neoplasm is composed of two cell populations (7, 13, 14). 
Electron rnicroscopy reveals, first, marked proliferation of 
capillaries with swollen endothelial linings that often occlude 
the lurnens. These newly formed vessels do not seem to be 
associated with a continuous basal lamina or with pericytes 
(7, 15, 16). 
A second population of spindle-shaped cells, still poorly 
defined from an ultrastructural point of view, then infiltrates 
the area surrounding these vessels. 
Another typical finding, especially in the early phases of 
the disease, is that of an inflarnmatory infiltrate composed of 
lymphocytes and plasma cells. This aspect of the disease 
becomes less evident with tirne, according to some 
investigators (15, 19, 21), although others have found that 
the infiltrates persist especially in those cases that are 
associated with AIDS (23). 
Electron rnicroscopy has demonstrated other features that 
are specific 10· Kaposi's sarcoma. Extravasated red blood 
cells, either single or in clurnps, can be seen in the dermis. 
Hyaline bodies, probably composed of erythrocytes, 
platelets and other substances deri ved from either blood (19, 
24) or tissue (fibrinogen, factor VID, AlAt, CEA, AFP) are 
also found. 
The above features have been observed in both sporadic 
and epidernic forms of Kaposi's sarcoma. Most authors (14, 
18, 22) agree, in fact, that the two forms are identical from an 
ultrastructural point of view. Virus particles that 
morphologicallyresembleHTL V-ill virushave beenobserved 
in the neoplastic cells of AIDS-related Kaposi's sarcoma and 
are considered by some (13) to be pathognomonic for this 
form of the disease. However, the importance of this finding 
is stili open to debate. 
Normal endothelial cells (25) are characterized by 
72 
micropinocytotic vesicles, multivesicular bodies, Weibel-
Palade corpuscles, gap and tight intercellular junctions and a 
continuous basal lamina (26, 27). These latter organelles, 
studied for the first tirne in 1964, are considered to be 
ultrastructural markers for endothelials cells. Certain 
investigators who have studied the functions ofthe Weibel-
Palade corpuscles believe that they areinvolved in coagulation 
as storage areas for platelet factor ill (28) or, as suggested 
more recently, for von Willebrand's factor VID (29). 
These characteristics are absent or modified in the 
endothelial cells of the newly formed vessels of Kaposi's 
sarcoma. The intercellular junctions are altered and in some 
cases broken, and there are few organelles within the 
cytoplasm. 
The basal lamina appears fragmented and in some cases is 
absent (18). 
In addition to these alterations, the endothelial cells of 
AIDS-related Kaposi's sarcoma contain tuboloreticular 
structures identical to those that were first described in the 
1960's in human lymphoid cells (30). These structures have 
also been found in peripheral blood mononuclear cells from 
patients with various pathological conditions, including 
Figure 1: Early lesion from classical Kaposi's sarcoma: 
Weibel-Palade bodies and MVB are well evident in the 
cytoplasm. The basal lamina membrane around the cel/s 
appears almost normal (Original magnification 4600x). 
ac/a dermalovenerologica AP.A. Vol 2, 93, No 3 
Kaposi's sarcoma, c/assic and AIDS related 
autoimmune diseases, viral infections and neoplasms (31). 
There is an important correlation between the abnormal 
serum levels of alpha-interferon and the presence of 
tuboloreticular structures in patients with lupus erythematosus 
(31). Abnormally high serum levels of alpha interferon, and 
according to some authors (32), beta interferon, as well, are 
found in alrnost ali AIDS patients in which tubuloreticular 
structures appear in either lymphoid or endothelial cells. 
There is thus basic agreement over the ultrastructural 
identity of the two forrns ofKaposi's sarcoma, although some 
investigators place more value than others on the finding of 
HfL V-III like-virus particles in cells from the AIDS-related 
form of the disease (35). 
MATERIALS AND METHODS 
W e have recentl y used electron microscopy to examine the 
ultrastructural features of lesions from patients with the 
classical form of Kaposi's sarcoma and from others with 
Figure 2: Early lesion in AIDS-related Kaposi's sarcoma: 
involvement of endothelial cells is manifested by cytoplasmic 
necrotic phenomena.Around the vessel the pericyte shows an 
enlarged cytopl,asm and well developed RER (Original 
magnification 6200x). 
acta dermatovenerologica AP A. Vol 2, 93, No 3 
AIDS-related disease. 
The study was undertaken in an attempt to identify 
ultrastructural parameters of differentiation between the two 
forms as well as to learn more about the histogenesis of this 
singular neoplasm. 
On the basis of clinical data as well as that of histological 
parameters described recently by Bisceglia et al. (41), we 
divided ali available specirnens into the the following three 
categories: early growth-phase, mature growth-phase and 
aggressive growth-phase. 
A total of25 biopsies ofKaposi's sarcoma were exarnined: 
twenty-three of these specirnens came from male patients and 
the other two were from females. 
Twenty of the cases were classical forms of the neoplasrn; 
five were from patients with AIDS. 
Ali samples were fixed in Karnovsky solution buffered to 
a pH of 7 .2 with cacodyl sodium. They were then fixed in 
osmium tetraoxide, dehydrated and embedded in an acrylic 
resin according to the method of Spurr. 
Ultrafine sections (thickness 45-65 nanometers) were then 
cut with an U!tracut E ultramicrotome (Reichen Jung), 
stained with uranyl acetate and lead citrate and examined 
with a Philips electron microscope. 
RESULTS 
EARL Y GROWTH-PHASE LESIONS 
Classic Kaposi's sarcoma: the principal alteration noted in 
the early lesions was that of the endothelial cells of the 
smaller capillaries. The volume ofthese cells was markedly 
increased. The cytoplasm protruded into the lumen of the 
vessels, and in many cases totally occluded them. Nuclear 
volume was also increased, and the nuclei themselves had a 
dentate appearance. 
Weibel-Palade corpuscles were present near the few 
mitochondria. 
The basal lamina of the involved capillary was normally 
present. 
The pericytes norrnally found around capillaries were 
sometimes absent (Fig. 1). 
Within the early lesions of sporadic Kaposi's sarcorna, 
normal capillaries which had not yet become involved in the 
sarcomatous process could also be observed. 
AIDS-related Kaposi's sarcoma: the ulu·asuuctural features 
of these specimens were, for the most part, similar to those of 
classic Kaposi's sarcoma. However, necrosis of the endo-
thelium was more common in these specimens. Tubu-
loreticular suuctures appeaiing asa continuation of the rough 
endoplasmic reticulum were also consistently seen. Necrosis 
oftheendothelium was occasionally accompanied by leakage 
of erythrocytes into the smrnunding dennis. 
The pericytes, were often absent or modified. The latter 
73 
Kaposi's sarcoma, c/assic and AIDS related 
were enlarged and contained well-developed rough 
endoplasmic reticulum in their cytoplasm. Numerous 
reduplications of the basal lamina were noted (Fig. 2). 
Figure 3: The microphotography shows the reduction of the 
intercellular junctionand ofthe intracytoplasmic organe/les 
(Original magnification 6200x). 
MATURE GROWTH-PHASE LESIONS 
Classical Kaposi's sarcoma: Ultrastructural examination of 
the lesi on at this stage revealed definitive breakdown of the 
vascular structure. The endothelial celi s had a totall y abnorrnal 
appearance. The cytoplasm contained very few organelles 
and was often involved in necrotic processes. 
The Weibel-Palade corpuscles were still present. The 
nucleus had become oval in shape with finely dispersed 
chromatin. There were far fewer intercellular junctions, and 
erythrocyte diapedesis had increased. The flattened red cells 
could be seen among the swollen endothelial cells surrounding 
the almost virtual lumen of the capillary. Tubuloreticular 
inclusions could be found in only a few of these specimens 
(Fig. 3). 
The basal membrane was clearl y reco gnizable but appeared 
fragmented and in some cases doubled. There was an 
74 
additional reduction in the number of pericytes, and their 
cytoplasmic processes were in contact with the basal 
membrane in only a few points around the capillaries. 
Figure 4: Extravasated erythrocites and spindle-shaped 
cel/s withf ew intracytoplasmic organelles are shown in these 
pictures. The spindle-shaped cells present only a fragmentecl 
basal lamina (Original magnification 4600x). 
Numerous erythrocytes undergoing phagocytosis were 
seen in the dermis around blood vessels. 
AIDS-related Kaposi's sarcoma: The cytoplasm of the 
endothelial cells contained almost no organelles with the 
exception of a few cistemae of the rough endoplasmic 
reticulum and an occasional saccule in the vicinity of the 
Golgi complexes. Around the blood vessels, the basal lamina 
could be seen only occasionally, and there were very few 
pericytes. Numerous erythrocytes could be observed within 
the surrounding dermis (Fig. 4). 
Aggregated tubuloreticular su·uctures (TRS) were fre-
quently found within the rough endoplasmic reticulum or as 
directextensions of it. In othercases weobse1ved "ve1micellar 
bodies" in cytoplasm of the endothelial cells (Fig. 5). The 
latter structure is made up of intenwining filaments or rod-
like elements. 
acta dermatovenerologica A.P.A. \lot 2, 93, No 3 
Kaposi's sarcoma, classic and AIDS related 
Spindle-shaped cells werepresent around the altered vessels. 
The oval nuclei of these cells were in central or polar 
positions, and there were veryfew organelles in the cytoplasm. 
Figure 5: In the cytoplasm of the endothelialcells intertwining 
filaments are found in the AIDS-related Kaposi's sarcoma 
(Original magnification 13000x). 
The insert shows as these structures are made by 
interconnecting filaments or rod-like elements (Original 
magnification 36000x). 
Weibel-Palade corpuscles were absent. In some cases, the 
spindle-shaped cells were loosely attached to one another 
forming one ortwo layer strips. The strips sometimes seemed 
to enclose small, vascularlike spaces that were optically 
empty (Fig. 6), 
AGGRESSIVE GROWTH-PHASE LESIONS 
Classic Kaposi's sarcoma: The predominant feature ofthe 
specirnens from older lesions was the presence ofnumerous 
spindle-shaped cells that were difficult to characterize from 
an ultrastructural point of view (Fig. 7). These cells had oval 
nuclei with chromatin dispersed in fine strands or, in some 
cases, clumped in the nuclear periphery. The cytoplasm 
acta dermatovenerologica A.P.A. Vol 2, 93, No 3 
contained few organelles and mitochondria. There were no 
multivesicular bodies or Weibel-Palade corpuscles. 
In some specimens (Fig. 8), individual cells were scattered 
Figure 6: Endothelial cells are joined to forma vascular-like 
structure with almost no lumen bounded by a basal membrane 
(Original magnification 8000x). 
throughout the dermis, whereas in others, they were arranged 
in rows. In other areas two such rows seemed to surround 
optically empty, vascular-like spaces, Throughout the field 
extravasatedred cells being digested by phagocytes could be 
observed. Intact capillaries were present in the midst of those 
that presented the alterations previously described in more 
recent lesions. 
AIDS-related Kaposi's sarcoma: In these lesions the great 
majority of the capillaries examined showed profound 
alterations. In some cases, spindle-shaped cells were seen 
loosely joined together and scattered throughout the tissue, 
Numerous extravasated erythrocytes could be seen among 
these cells (Fig. 9). 
Histiocytes and fibroblast-like cells showed phagocytosis 
of the red blood cells (Fig. 10). The spindle-shaped cells did 
not appear to contain viral particles but, in some cells. it was 
possible to observe ulu·asuuctural features 0f "vermicellar 
75 
Kaposi's sarcoma, classic and AIDS related 
bodies" and tubuloreticular structures, as we have already 
described in mature growth-phase lesions. 
DISCUSSION 
The ultrastructural study described here has allowed us to 
clarify some features of Kaposi's sarcoma. 
One of the major purposes of this study was to determine 
whether electron-microscopy could reveal differences 
between the two forms of this neoplastic process. 
Figure 7: Spindle-shaped cells with elongated nuclei and 
poorly characterized cytoplasm can be seen within the 
dermis (Original magnification 7200x). 
Our findings do not indicate any qualitative difference 
between the classic lesion and those associated with AIDS. 
However, the fact that certain features seemed to be more 
or less common in one form or another may be significant. 
The AIDS-related lesions seemed, in fact, to be associated 
with a more rapid and extensive destruction of endothelial 
structures of the capillaries. Capillary changes in lesions 
from patients with classical Kaposi's sarcoma evolved more 
gradually, and the degree of damage seen in the early AIDS-
associated lesions was reached only in the more advanced 
lesions of this type (13, 14). 
76 
Another finding that seemed to differentiate the two types 
of lesions was the increased frequency with which 
tubuloreticular inclusions were observed in the lesions 
associated with AIDS, a feature that has already been noted 
by others (13, 36). 
Various studies, in any case, consider the tubuloreticular 
structures just an indirect evidence of viral infection; in fact, 
it was possible to find this feature in cells affected by 
autoimmune diseases or after interferon-therapy (31, 32). 
Ali of the AIDS specimens we examined contained these 
Figure 8: Spindle-shaped cells and erythrocytes within the 
dermis. Some of the cells appearwhole while others are being 
phagocytized (Original magnification 7200x). 
structures as opposed to only two of those from the classic 
group, and in these laner cases, they were difficult to find. 
Wedidnot observe viral-likeparticles within the cells from 
AIDS-associated lesions, but we found "ve1micellar bodies" 
in the cytoplasm of these cells. The morphology of these 
plexiform inclusions is better appreciated in relatively thick 
sections; in extremely thin sections, it appears as dense 
granules that may be confused with clumps of disintegrating 
nuclear andnucleolar material. The diameters of the ve1micular 
rods are similar to those of viral cores. 
These inclusions are described, by some authors, in nucleus 
acta dermatovenerologica A.P A. Vol 2. 93, No 3 
Kaposi's sarcoma, classic and AIDS relaled 
or even in the cytoplasm of cells infected by respectevely 
DNA or RNA-virus and probably represent deranged or 
frustrated core-viral production (43, 44). 
We did not find "vermicellar bodies" or vira! particles in 
the classical form of Kaposi's sarcoma, whereas others ( 42) 
found vira! particles in this form of Kaposi's sarcoma in 
Greece. 
Another important objective of our study was that of 
clarifying the histogenetic origin of Kaposi's sarcoma. Our 
findings, togetber with those of the literature (33, 34, 3 7) , 
Figure 9: Spindle-shaped cells and extravasated erythrocytes 
characterize an advanced AIDS-related lesion (Original 
magnification 4500x). 
suggest that the process originates in endothelial cells. 
Whereas only a few of the spindle-shaped cells present in 
these lesions could be identified as endothelial cells on the 
basis of electron-microscopy findings, the results of recent 
irnmunohistochemical studies (38) revealed that the cells 
presented at least one of the characteristics of normal 
endothelial cells . 
acta dermatovenerologica A.P.A. Vol 2, 93, No 3 
This study (38) demonstrated the presence of the CD34-
antigens on severa! celi types, including dendritic cells of the 
dermis, perifollicular cells, and, more significantl y, endothelial 
cells; in Kaposi's sarcoma both the proliferating endothelial 
cells and those that are spindle-shaped present the CD34-
antigen. 
This finding, together with those ofFink (39) andNickoloff 
( 40), argue for an endothelial ratherthan fibroblast derivati on 
of these spindle-shaped cells. Certain properties, such as the 
capacity to form regular and well-defined vessels, are !ost 
Figure 10: Fibroblast-like cel/s engaged in phagocytosis of 
extravasated erythrocytes (Original magnification 4500x). 
during theneoplastic evolution and cells acquire other features 
that are more characteristic of fibroblast. This interpretation, 
together with the study conducted by Nickoloff et al. (40), is 
further supported by the fact that the ultrastructural similarities 
between the endothelial and spindle-shaped cells were greater 
in cells lying close or adjacent to one another than in those 
separated by greater distances . 
77 
Kaposi's sarcoma, c/assic and AIDS related 
REFERENCES 
1) Cerimele D, Massarelli G. In: Rondanelli E G: "AIDS la 
sindrome da immunodeficienza acquisita". Piccin Nuova 
libreria 1987, 1979-201. 
2) Smitch EC, Helmes B.G.T. Malignant disease in the 
natives ofNigeria. An analysis of 500tumors. Ann Trop Med 
Parasitol 1934 2, 28:641. 
3) Thijs A. L'angiosarcomatose de Kaposi au Congo Belgaet 
Ruanda Burundi. Ann Soc Belg MedTrop 1957; 37: · 
295-307. 
4) Centers for disease control. Update on acquired immune 
deficiency syndrome (AIDS) in United States. MMWR 1982; 
31:507. 
5) Ackerman B.A. 1985 Hystologic features of Kaposi's 
sarcoma and simulators of it. Kaposi's sarcoma D. Cerimele. 
Spectrum publication, inc. 
6) Otto H.F. et al.Kaposi's sarcoma and AIDS. Lightfeatures 
including cytoskeleton. Laryng Rhin Otol ·1985; 181: 88 
(ABSTR.). 
7) Murray J.L, Lothe F. The histopathology of KS. Acta Un. 
Jnt Cancer 1962; 18: 413-28. 
8) Hashimoto K, Lever W.F. K. Sarcoma; histochemical and 
electron microscopic studies. J invest De1matol 1964; 43: 
539-49 
9) Pepler W.J, Theron J.J. An elecu-on microscope study of 
KS hemangiosarcoma. J pathol bacteriol 1962; 83: 521-5. 
1 O) Dorfman R.F. the ultrastructure of KS. Lab. Invest 1964; 
13: 939. 
11) W aldo Ed, · E Coll. The ultrastructure of vascular tumor; 
additional observations and a review of the literature. Pathol. 
Annu 1979; 12 (2): 279-305. 
12) Tucker J.A. Malignancies in the AIDS. J. Electron. 
Microscop. Tech 1988; 8 (1): 137-58. 
13) Konrad K, Schenk P. et al . Tubuloreticular structures in 
Kaposi's sarcoma; a comparison of the classical and AIDS-
associated forms. Acta Derm. Vener. 1986; 66: 207-12. 
14) NewlandJRet al. Jntraoral Kaposi's sarcoma a correlated 
78 
lightmicroscopic, ultrastructural, and immunohistochemical 
study. Oral. Surg. Oral. Med. Oral. Pathol. 1988;6 6: 48-58. 
15) Schenk L, e Konrad K. ulu·astructure ofKaposi's sarcoma 
in AIDS. Arch. Otorhin. 1985; 242: 305-13. 
16) Schenk P. Ultrastructural morphology ofKS in the head 
and neck region of patient with AIDS. Laryng. Rhin. Oto! 
1986; 65: 604-11. 
17) Kostianowsky M, Kangy H, Grimley PM. Disseminated 
tuboreticular inclusions in acquired immunodeficiency 
sindrome (AIDS). Ultrastruct Pathol. 1983; 4: 331-6. 
18) Leu HJ, Odermatt EB . Multicentric angiosarcoma. 
Virchows Arch. (Pathol. Anat.) 1985; 408: 29-41. 
19) McNutt N. S, Van Fletcher, Conant M. A. Early lesions 
of Kaposi's sarcoma in homosexual men. An ultrastructural 
comparison with other vascular proliferations in skin". Am. 
J. Pathol. 1983; 111: 62-77. 
20) Bendelac A, Kanitakis J. et al. Basement membrane in 
KS.; an immunohistochemical and ultrastructural study. 
Path. Res. Pract. 1985; 180: 626-32. 
21) Kuntz AA, Gelderbrom HR et al. Ultrastructural findings 
in oral Kaposi's sarcoma (AIDS). J. Oral Pathol. 1987; 16: 
372-9. 
22) Ackerman AB. Subtle clues to diagnosis by elecu·on 
microscopy; the patch stage of Kaposi's sarcoma". Am. J. 
Dermatopathol. 1979; 1: 165-72. 
23) Schulze H.J. et al. Initial lesions ofHIV related Kaposi's 
sarcoma - a histological, Immunohistochemical, and 
ultrastructural study". Arch. Dermatol. Res. 1987; 279: 
499-503. 
24) Massarelli G et al. Hyaline bodies in Kaposi's sarcoma: 
an immunocytochemical and ultrasu·uctural study''. Appl. 
Pathol 1989; 7: 26-33. 
25) Pathobiology of cell membranes, II, 1980, edited by BF 
Trump / A.U. Arstilia. Pag. N. 429. 
26) Weibel E.R. Neue cytoplasmatische Komponenten von 
Endotelzellen". Acta Anat. 1964; 59: 390. 
acta dermatovenerologica AP.A. Vol 1, 93, No 3 
Kaposi's sarcoma, classic and AIDS related 
27) Weibel ER, Palade GE. "New cytoplasmic components 
in arterial endothelia" J. Cell. Biol. 1964; 23:101-12. 
28) Siegel A and Liischer EF. Non identity of the a granules 
of human blood platelets with typical lysosomes". Nature 
1967; 215:745-47. 
29) Warhol M.J. The ultrastructural localization ofWillebrand 
factor in endothelial cell". Am. J. Pathol. 1984 117: 310-15. 
30) Schaff Z., Barry D.W. et al. Cytochemistry of 
tuboloreticular structures in lymphocites from patients with 
sisternic lupus erythematosus and in human lymphoid cells" 
Lab. lnvest 1973; 29: 577-86. 
31) Grimley P.M., Schaff Z. Significance of tubuloreticular 
structures in the pathobiology ofhuman disease. Pathobiol. 
Annu 1976; 6: 221-57. 
32) Grimley P.M. et al. TRS in patients with AIDS inter-
feron-related effects in circulating t cells monocytes" in: 
Friedman-Kien AE, Laubenstein L. J..: "AIDS: The epidemic 
ofKaposi's sarcoma andopportunistic infections"New York, 
Masson publishers U.S.A. inc. 1984; 181-92. 
33) Safai B. Kaposi's sarcoma; an overview of classical and 
epidernic forms. In: Broder S. Ed.: AIDS, modem concept 
and therapeutical challenges. Basel, Dekker 1987: 205. 
34) Russel Jones R, Spaull J et al. Histogenesis ofKaposi's 
sarcoma in patients with and without acquired 
immunodeficiency syndrome (AIDS). J. Ciin. Pathol. 1986: 
39: 742-9. 
35) Gyorkey F, Sinkovics H. G, Melnick J. C, Gyorkey P. 
Retroviruses in KS in AIDS. (Letter). N. Engl. Journal of 
Med 1984; 311: 1183-4. 
36) Marquart K. H. Tubureticular structures in Kaposi's 
sarcoma cells are not an ultrastructural marker for AIDS. 
(Letter) ActaDerm Venereol 1987; 67: 367. 
37) Nadji M. et al. KS immunohistologic evidence for an 
endothelial origin. Arch. Pathol. Lab. Med. 1981; 105: 
274-5. 
38) NickoloffBJ. Thehuman progenitorcell antigen (CD34) 
is localized on endothelial cells, dermal dendritic cells and 
perifollicular cells in formalin-fixed normal skin and on 
proliferating endothelial cells and stromal spindle-shaped 
cells in Kaposi's sarcoma. Arch Derm 1991; 127: 523-529. 
39) Fink L. et al. Expression of the CD-34 gene in vascular 
endothelial cells. Blood 1990; 75: 2417-26. 
AUTHORS' ADDRESSES 
Dr. Leonardo Celleno, Dept. of Dermatology Catholic University of Sacred Heart 
Largo A. Gemelli, 8 - 00168 Rome, Italy 
A. Mas1rnianni M.D. san1e address 
M. G. Borgia M.D. same address 
D. Cerimele M.D. same address 
F. Cottoni M.D. Dept. ofDermatology, University of Sassari, Sassari, Italy 
acta dermatovenerologica A.P A. Vol 2, 93, No 3 79