ELECTRON MICROSCOPIC STUDY OF XANTHOMA CELLS* TAMOTSU IMAEDA, M.D.
nuclei. The cytoplasm contains a number of lipid
The xanthoma cell, which is one of the lipid
drops stained red by Nile blue. All drops show by light microscopy. However, with the resolv- double refractile property under the polarization ability of light microscope, it is difficult to con- microscopic observation. Neither giant cells nor deposited cells, has been studied histochemicall3l
firm the morphological process of lipid deposition
eosinophilic cells are demonstrated in this lesion.
ultra-thin sectioning has been of value.
seminata and eosinophilic granuloma. Xanthoma
Concerning xanthomatous tissue of skin, in the xanthoma cell. In order to facilitate the study of the cytoplasmic elements of this cell, many workers have mentioned following three the application of the electron microscope and diseases: xanthoma tuberosum, xanthoma dis-
This paper is a study of some structural tuberosum is one of the lipidoses and the other changes which appear in the xanthoma cell and the development of lipid droplets which has been elucidated by electron microscopy and ultra-thin
two diseases belong to the group of primary
xanthoma tuberosum, is easily distinguished from other two diseases by the absence of eosinophilic cells which is characteristic of eosinophilic granuloma, and by the clinical picture which is different from that of xanthoma disseminata.
reticuloendothelial diseases (3, 5, 10, 12, 13).
MATERIAL AND METHODS
The lesion investigated in the present study,
Specimens of xanthoma were obtained from one
of yellow nodules of the elbow of twenty four years old female. The tissue was cut into small chips and immersed in 1% osmium tetroxide solution buffered with phosphate at pH 7.4 and
INTERPRETATION OF ELEcTa0N MIcEOGRAPH5
The electron microscopic observation demonstrates xanthoma cells to be modified forming intricate pseudopods and comprising numerous large clearly defined vacuoles (Fig. 1). These vacuoles show a lucent appearance and are delimited by an electron-dense membranous layer. Some vacuoles contain less dense masses in the interior (Fig. 3). Moderately dense bodies, which show round or oval shapes and are spotted with denser substances, are distributed together with vacuoles.
prepared to be isotonic with sucrose.
After the fixation for 4 hours, tissues were dehydrated with aceton in refrigerator for 1 hour without washing and immersed in a mixture of n-butyl methacrylate (60%) and methyl methac-
rylate (40%) at room temperature for about 30 minutes. The samples were then polymerized at 550 C for 5 hours. Ultra-thin sections were made with Nippon lJltra-microtome and the thin sections were mounted on copper grids covered with
formvar. The electron microscope used in the present investigation was Akashi Tronscope They measure 400—900 mji in diameter and are usually not limited by membranes (Fig. 2). Occa-
model 50. In order to examine with histocbemical technics, tissues were fixed with 10% formalin solution and frozen sections were made. Sections were observed
with polarization microscope and some of them were stained by the use of Nile blue.
sionally mitoehondrial cristae-like textures are resoluted in their matrices (Fig. 5). Besides these figures, volute or onion-like figures are visible in the cytoplasm. A transitional figure, which is modified to contain the
lucent areas in dense bodies, is also found
Biopsied tissue consists of numerous foamy cells which arc packed closely in masses between collagen bundles. These large foamy cells have
(Fig. 2, Fig. 4). Distinguished from the aggregation of Palade's particles, moderately dense smaller substances,
thought to be pinocytotic lipid droplets, are granular cytoplasm and large round or oval dispersed in the cytoplasm and develop a tendency to coalesce with each other (Fig. 2).
From the Instituto Venezolano de Investi-
gaciones Cientificas, Caracas, Venezuela, and the Leprosy Research Laboratory, Kyoto University School of Medicine, Kyoto, Japan. Received for publication August 6, 1959. 331
Cytoplasmic organdIes are abundantly observed, being compacted by numbers of vacuoles
and dense bodies. Mitochondria are easily distinguished by their distinctive structure from
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Fin. 1. Xanthoma cell contains dense bodies and vacuoles, and possesses intricate pseudopods. Collagen bundles (C) are located near the cell.
the dense bodies and are infrequently situated adjacent to vacuoles (Fig. 3). Neither swelling of mitochondria nor osmiophilic inclusions can be noted. Organized ergasto-
plasms are distributed in large numbers, but the evidence which indicates an intimate correlation with lucent vacuoles is not observed. The Golgi complex consists mostly of flattened sacs and vesicles. It seems likely that this apparatus has
deposits result from the uptake of increased blood cholesterol, or from the increased supply of
blood cholesterol. The former corresponds to xanthoma tuberosum, while the latter corresponds to eosinophilic granuloma and xanthoma disseminata (8, 9, 10, 11, 12, 13). Since the mate-
rial examined in the present study is xanthoma tuberosum, the mechanism of lipid deposition may belong to the increased uptake of blood
no real connection with the large vacuoles lipids. The electron micrographs exhibit various (Fig. 2). Collagen fibrils are present in the extracellular figures in the cytoplasm of xanthoma cells: environment of xanthoma cells. Surrounded with namely dense bodies, volute or onion-like figures collagen fibrils, dark smaller cells arc also located. and lucent large vacuolcs. Generally dense bodies These cells may belong to the group of fibro- are observed in cells containing a small number cytic cells (Fig. 6). Frequently these dark cells of vacuoles. In addition to the occurrence of dense
contain both dense bodies and lucent vacuoles (Fig. 7). On the light microscopic level, they are not distinguishable from xanthoma cells which have light cytoplasm as described earlier. DIscussIoN
bodies, numerous smaller dense substances, thought to be pinocytotic droplets, are distributed in cytoplasm. These pinocytotic droplets coalesce with each other and develop into dense bodies. This process is similar to that of the formation of opaque droplets in lepra cell,
Regarding the occurrence of foamy cells in which is one of lipid deposited cells (5). It is assumed, therefore, that the occurrence of xanthomatous tissues, it is believed that lipid
- • ft
V • - t.11
2. One of young xanthoma cells. Dense bodies (D) are spotted by denser substances. Lucent
areas appear in some dense bodies. Volute figures (Vf) and lucent vacuoles (V) are also exhibited in the cytoplasm. Golgi complex (G) is situated near these figures, but does not indicate positive correlation with both dense bodies and vacuoles. Excepting distinctive dense bodies, pinocytotic droplets are distributed and show a tendency to coalesce with each other (arrow).
t -C p
FIG. 3. One of well developed xanthoma cells. Lucent large vacuoles (V), delimited by membranous layer, occupy almost all area of cytoplasm. Mitochondria (M) are in contact with these vacuoles but the intimate relationship is not visible between them. Small number of dense bodies (D) are also demonstrated. Enclosing xanthoma cell, collagen bundles (C) are observed. 334
4., 'it,,. ,
FIG. 4. Picture shows minute vesicles in dense
FIG. 5. Mitochondrial cristae-like texture is
resoluted in dense body (arrow).
:i' I., -
At Fxo. 6. In the surroundings of well developed xanthoma cell, smaller dark cells, thought to be fibrocytic cells, are observed. They show the intimate correlation with collagen bundles (C).
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st Fcc. 7. Dark xanthoma cell (upper right) and light xanthoma cell (lower left) are exhibited in this
picture. In dark cells, cytoplasmic organelles are more compacted with numbers of characteristic figures.
numbers of pinocytotic droplets and of dense As a result, it seems likely that there is not an bodies is indicative of the fact that these cells intimate relationship between mitochondria and are the incipient stage in the process of lipid dense bodies in xanthoma cells. The cristae-likc texture in dense bodies may represent a certain deposition. In dense bodies, minute lucent vesicles appear profile of lipid metabolism of mitochondria which was suggested by Lever in the study of adreno-
frequently. The intermediate figures between them and volute figures are also found. From
cortical cells and also by Imaeda in fat cells
these findings, it is believed that volute or onion-
(4, 7), or it may represent a micelle formation of
like figures arise from the vesiculation in lipoprotein in dense bodies. dense bodies. With the further development of these changes,
volute figures grow into lucent vacuoles. In the mature xanthoma cells, in which large vaeuoles occupy almost all areas of cytoplasm, the decrease of distribution of dense bodies is noted. This evidence also suggests that dense bodies are converted to lucent vacuoles. Concerning mitochondrial appearance in lipid deposited cells, it has been elucidated that mito-
Concerning the correlation between submicroscopic structures mentioned above and chemical
components, it is not easy to determine which components correspond to any of the following: cholesterol, its esters, neutral fat, and phosphatide, etc. According to Bahr and Imaeda (1, 2,
4, 5), free cholesterol shows a slight osmiophilic property, but organic substances containing unsaturated fatty acids give a dense or moderately chondria combine with lipid and change to osmio- dense appearance under the condition of osmic philic substances surrounded by double mem- acid fixation and electron microscopic observabrane (4, 6, 7). In xanthoma cells, infrequently tion. Based on these results, it is apparent that
dense bodies have cristae-like texture in their electron transparent vaeuoles do not contain matrices. But the transitional figures between unsaturated fatty acid but that dense bodies are mitochondria and dense bodies do not appear. composed of unsaturated fatty acid. The problem
of the localization of cholesterol and its esters, however, remains unresolved. SUMMARY
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THE JOURNAL OF INVESTIGATIVE DERMATOLOGY
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