Ultrastructure of Human Chordoma

(CANCER RESEARCH 28, 2115-2125, OctOber 1968]

Ultrastructure of Human'

RobertA. Erlandson, Bernard Tandler,2Philip H. Lieberman, and Norman 1.Higinbotham Division of Cytology, Sloan-Kettering Institute for Cancer Research, and Department of Pathology and the Bone Service of the De partment of Surgery, Memorial Hospital for Cancer and Allied Diseases, New York, New York 10021

SUMMARY published (5, 15, 29) ; each deals with a single case. The present article describes the fine structure of three sacrococcygeal Three sacrococcygeal chordomas, two of which were recur chordomas, with special emphasis on a unique complex of cyto rent, were examined by electron microscopy. The three tumors, plasmic organelles which was observed in each case. which were quite similar, consisted of cords, lobules, and clusters of cells embedded in a mucinous matrix. The so-called stellate MATERIALS AND METHODS and physaliferous cells represented the extremes of a develop mental sequence of tumor cells and were separated by a spec Specimens of sacrococcygeal chordomas were obtained from trum of morphologically intermediate cells. The physaliferous three patients by aspiration biopsy. Their case histories are cells appeared to arise from the stellate cells by a process of briefly summarized below: progressive cytoplasmic vacuolization. Some of the resulting Case 1. The patient was a 78-year-old white Jewish male vacuoles were so large that the nucleus and the cytoplasmic or who in 1950 underwent partial sacrectomy because of chordoma. ganelles were displaced to the cell periphery. Many vacuoles He remained symptom-free until 1965, when recurrent tumor contained deposits of glycogen. necessitated cobalt-60 therapy (6300 made, tumor dose) . The The most striking feature of the tumor cells was the consist tissue specimen was obtained late in 1966 about three hours ent association of mitochondria and endoplasmic reticulum in a after a single treatment of 300 mads. structurally ordered complex. In such complexes, single mito Case 2. The patient was a 60-year-old white Jewish female chondria alternated with single cistemnae, each organelle being who had undergone a partial sacrectomy for chordoma after separated from its neighbor by an interval of constant width. six months of rectal pain. The present specimen was from a The central portions of the mitochondria were so flattened that recurrent lesion removed in 1966. No radiotherapy had been the limiting membranes of opposite sides almost met ; at their given. ends, the mitochondria were bulbous and possessed a few Case 3. The patient was a 65-year-old white Jewish male angulated cristae. Beyond the lateral boundaries of the complex, who in 1966 underwent partial sacrectomy because of the the cisternae abruptly became smooth surfaced. The function presence of a chordoma. The specimen was obtained without of these unusual complexes is unknown. antecedent radiotherapy. For electron microscopy, small blocks of tissue were fixed INThODUCTION for one hour in a mixture of 2% acrolein and 6% glutaraldehyde (28) and postfixed for one hour in 2% osmium tetroxide (24) Chordoma, a tumor which usually appears in middle or late with added sucrose (7) . Both fixing solutions were buffered adult life, arises from remnants of the embryonic notochord with veronal acetate. After dehydration, the specimens were (20, 27) . The majority of these tumors occur at sites corre embedded in Maraglas-Dow Epoxy Resin 732 (11) . Thin see sponding to the ends of the notochord, 45 to 56% of reported tions were doubly stained with methanolic uranyl acetate (30) cases occurring in the sacrococcygeal region (25, 32) . While of and with lead citrate (26) , and were examined in a Siemens low malignancy, chordomas have a tendency to be locally in Elmiskop I electron microscope. vasive and destructive. A recent report by Higinbotham et at. Specimens for routine light microscopy were fixed in phos (19) has shown that following surgical removal, local recur phate-buffered formalin, embedded in paraffin, and stained with rences and metastases commonly occur. hematoxylin and eosin. Half-micron thick sections of epoxy Although the light microscopic characteristics of human embedded tissue were stained with toluidine blue using the chordomas have been described in numerous articles (6, 10, 12, method of BjÃ¶rkman (2) . Photomicrographs were taken with 14, 17, 31 ) , few studies of their ultrastructural organization a Zeiss standard WL microscope. have appeared. To date, only three such works have been OBSERVATIONS 1 This investigation was supported in part by Grant CA-08748 Light Microscopy from the National Cancer Institute, NIH. 2 Present address : School of Dentistry, Case Western Reserve In hematoxylin and eosin-stained paraffin sections, the tumors University, Cleveland, Ohio 44106. appeared to consist of two distinct cell types. The larger cell Received December 20, 1967; accepted June 13, 1968. type contained prominent vacuoles, and it is because of this

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feature that they are called â€œphysaliferouscells.â€•The smaller, The most striking feature of all the tumor cells was the con spindly cells, which appeared to be nonvacuolated, are usually sistent association of mitochondria and endoplasmic reticulum referred to as â€œstellatecells.â€•Both cell types, intermixed, were in a structurally ordered complex (Fig. 11) . In such a complex, arranged in cords, lobules, and clusters (Figs. 1, 2) . The rela single mitochondria alternated with single ergastoplasmic cis tive proportion of the two cell types varied from tumor to tu ternae, each organelle being separated from its neighbor by an mom and also in different sites within each specimen. The cell interval of approximately 500 A. As many as 10 layers of mito groupings were separated by a homogenous, mucinous matrix, chondria and 10 cistemnae were observed in some arrays. The and in one specimen they were surrounded by fibrous connec mitochondmia usually were long (about 2.3 @z)and dumbbell tive tissue as well as matrix. shaped. In their central portions, they were so attenuated that Much greater detail could be discerned in the thinner, tolu membranes of opposite sides almost met. At such points the idine blue-stained epoxy sections (Figs. 3â€”5).Not only physalif total thickness of the mitochondria measured as little as 340 erous and stellate cells were apparent, but a spectrum of A. The bulbous ends of the mitochondria were 10 times as morphologically intermediate cells as well. While the latter cells thick, measuring about 3400 A. These end portions frequently resembled stellate cells in form, they also possessed small cyto contained a few angulated cristae. The cistemnae were of the plasmic vacuoles. Many of the physaliferous cells contained rough-surfaced variety (RER), but at the lateral boundaries such large vacuoles that they assumed a typical â€œsignetringâ€• of the complex, which can be defined as the point where the shape (Fig. 3) . Some of the larger vacuoles contained a floe mitochondria end, the membranes abruptly became smooth culent material (Figs. 4, 5). (Figs. 13, 14) . In many cells, especially the physaliferous cells, The nuclei of the tumor cells frequently were highly irregular the smooth endoplasmic reticulum (SER) ramified throughout in size and contour. Many were multilobulated or had deep the cytoplasm (Figs. 7, 13). clefts. Occasional cells appeared to be binucleate. Intranuclear Solitary mitochondria, as well as solitary elements of RER, inclusions were present in many of the tumor cells, irrespective were infrequently seen. In contrast, a single distended cistern of cell type (Fig. 5) . These inclusions consisted of either a was frequently observed with several mitochondria in close dense spherical structure delimited by a light halo or a large relation (Fig. 12) . In such cistemnae, ribosomes were present mass of intermediate density surrounded by a very dense rim. primarily where mitochondria were apposed to the cistemnal The matrix, which appeared to be structureless, was stained membrane ; at other sites, the membranes usually were smooth. pink by the metachromatic toluidine blue, a tinctorial response Golgi complexes were present in many of the tumor cells, which was not shared by any other component of the tumors. being most abundant in the physaliferous cells, where they were usually situated near to or contiguous with the cytoplasmic Electron Microscopy vacuoles (Fig. 15) . The Golgi complexes consisted of closely Specimens from each of the three tumors studied were very packed, smooth cistemnae showing many fenestrations. Small similar at the ultrastructural level and are therefore described vesicles were numerous, and some were observed that were in composite. The electron microscope observations confirmed either budding or fusing with the Golgi cistemnae (Fig. 16). that stellate and physaliferous cells are not disparate cell types, Similar vesicles were sometimes joined to the limiting membrane but are related by a continuum of intermediate cells. Never of the vacuoles. theless, for the sake of convenience, this terminology is retained Many of the cytoplasmic vacuoles, large and small, con in this report. tamed glycogen (Figs. 6, 11) . Clusters of glycogen also were The aggregations of tumor cells were easily recognized at low abundant in both intermediate and physaliferous cells in those magnifications (Fig. 6) . The cells were irregular in outline, cytoplasmic areas which were rich in SER (Fig. 7) . Stellate frequently being locked together by interdigitating cellular cells contained little glycogen or SER, their cytoplasm being processes (Fig. 6, 7) . These processes often extended deep into characterized instead by the presence of bundles of tonofila adjacent cells. Desmosomes occasionally were present at such ments. sites. The extracellular matrix, at lower magnifications, appeared The nuclei of the tumor cells also were extremely irregular structureless, but it exhibited considerably greater electron in form. Deep incursions of cytoplasm gave many of the nuclei density than the vacuolar contents, exclusive of the glycogen. a multilobulated appearance (Figs. 8â€”10). These cytoplasmic At higher magnifications fine fibrils and granular material could intrusions, when viewed in cross-section, appeared as intra be observed scattered throughout the matrix. nuclear inclusions (Figs. 8, 9) . Such pseudoinclusions could be readily distinguished from true intranucleam inclusions for the DISCUSSION following reasons : (a) They were bounded by the nuclear en The mitochondrial-endoplasmic reticulum (MER) complexes velope, hence were delimited by two membranes. (b) They described in the prescnt study constitute the most prominent frequently were encompassed by condensed chromatin. (c) and striking ultrastructumal feature of the cells of human Nearly all contained cytoplasmic components .such as mito chordoma. These structures, which consist of alternating layers chondria and endoplasmic reticulum. True intranuclear inclu of RER and attenuated mitochondria, have not been described sions, on the other hand, were bound by a single membrane previously in any vertebrate cell type. A similar-appearing with no adjacent condensed chromatin and usually had an complex was illustrated, but not discussed, in a report on the empty appearance (Fig. 10) . Such inclusions were relatively fine structure of the corpus allatum of the moth of the silk @@ rare. worm, Bombyx mon (16).

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While among vertebrates the MER complexes appear to â€˜be demonstrated by the great difference in electron density be limited to chordoma cells, several examples of MER arrays, tween the two sites. In addition, the vacuoles remain unstained albeit of a somewhat different configuration, have been recog in 0.5-@&-thicksections stained with toluidine blue, while the nized in other cells. These occurred in the hepatic cell.@of rats matrix is stained an obvious pink. subjected to several different experimental procedures, includ Previous studies with the light microscope demonstrated the ing prolonged starvation (22), copper intoxication (1), and presence of glycogen in chordoma cell vacuoles by staining with partial hepatectomy (8) . Like the MER complexes of chordoma, Best's carmine (6, 9) or by the periodic acid-Schiff technic with the hepatic arrays consist of elements of endoplasmic reticulum diastase controls (9, 12) . These observations were confirmed alternating with elongated mitochondria. Although they are in by the present study. In the electron microscope, the vacuolar direct continuity with RER beyond the limits of the mito glycogen is momphologically similar to the glycogen in tie cyto chondrial stack, the cistemnal elements in the array are of the plasmic ground substance. The latter glycogen is in close topo smooth-surfaced variety, the exact reverse of the situation in graphic relation to the abundant SER, but, as in liver cells chordoma. Furthermore, instead of being separated from the (21), it is lodged in the interstices of the tubular reticulum mitochondria by an interval of fairly constant width, the and is not actually enclosed by membranes. In other cell types, smooth membranes are closely applied to the outer surface of glycogen occasionally has been observed engulfed by autophagic both sides of the mitochondria. Since the mitochondria also vacuoles (23) . However, the presence of a single unit membrane possess longitudinally oriented cristae, the result is a densely delimiting the chordoma cell vacuoles shows that these struc packed stack of membranes in which the precise identity of tures are not of the autophagic variety. If, in chordoma cells, individual membranes is not readily discernible. the two classes of glycogenâ€”vacuolar and cytoplasmicâ€”are At a simpler morphologic level, single cistemnae of endo identical, then the mode of entry of the cytoplasmic glycogen plasmic reticulum frequently have been observed in association into the vacuoles is unknown. with single mitochondria (13, 18). Such cistemnae parallel the In addition to cytoplasmic vacuoles, intranuclear vacuoles outer membrane of the mitochondria but are separated from also are present in chordoma cells. In the case described by the mitochondria by a gap equal to the intercisternal distance Friedmann et at. (15), some nuclei contained â€œpatchyâ€•in observed in parallel arrangements of RER, such as those found clusions of unknown nature. We have also observed several in exocrine cells. Fawcett (13) has suggested that in normal of these structures, and they apparently correspond to the cells, closely related mitochondria and RER cisternae may class of nuclear inclusions termed â€œsphaeridionsâ€•by BÃ¼ttner signify a transient juxtaposition of the mitochondrion to a local and Horstmann (4), which are widely distributed in many site of energy utilization. However, the paucity of solitary species of normal and pathologic cells (3). In the chordoma mitochondria and solitary cistemnae in chordoma cells strongly studied by Spjut and Luse (29), a different type of intra indicates that the MER complexes are not transient structures. nuclear inclusion was present ; this was described as an area The functional significance of the MER complexes is not of cytoplasm trapped within the nucleus. In our material sun clear. It is obvious that stratification of the organel!es brings ilar configurations were common. It was clearly evident, how the maximum surface area of RER membranes into juxtaposi ever, that such inclusions were in direct continuity with the tion with mitochondria. Fig. 12 demonstrates that the presence cytoplasm and that they in fact represented cross-sections of of attached ribosomes is directly related to mitochondrial villiform cytoplasmic extensions. In addition to these pseudo propinquity. It is possible, though no direct proof exists, that inclusions, several examples of true intranuclear inclusions were in chordoma cells a high concentration of ATP is necessary to observed in the present study. These usually appeared as keep ribosomes attached to the membranes of the endoplasmic watery vacuoles bounded by a single membrane. Like the cyto reticulum. plasmic vacuoles, the cytogenesis of the nuclear vacuoles is Whatever their functional status, the MER complexes con unclear. stitute convenient morphologic markers. It is highly improb able that so unusual a structure could arise independently in ACKNOWLEDGMENTS unrelated cell types. Their presence in almost every cell in the The expert technical assistance of Roy R. Keppie and Mona three cases studied is compelling evidence that the different Brandreth is gratefully acknowledged. cell types are directly related and that they probably represent a developmental sequence. REFERENCES The progressive increase in the degree of vacuolization also supports the concept of a single cell type in chordoma. Small 1. Barka, T., Scheuer, P. J., Schaffner, F., and Popper, H. Stmuc vacuoles, which are present in the stellate cells, increase in tural Changes of Liver Cells in Copper Intoxication. Arch. dimension in the intermediate cells and may attain enormous Path., 78: 331â€”349,1964. size in the physalifemous cells. There is no doubt, as Cancilla 2. BjÃ¶rkman, N. Low Magnification Electron Microscopy in His et at. (5) have observed, that many of the larger so-called to!ogical Work. Acta Morphol. Neer!. Scand., 4: 344-348, 1962. vacuoles apparent in routine light microscopic preparations are 3. BÃ¼ttner, D. W. Haben die Sphaeridien in den Zellkernen Kran ker Gewebe Eine Pathognomische Bedeutung? Virchows Arch. in reality large extracellular spaces demarcated by cell proc Pathol. Anat. Physiol. Klin. Med., 543: 142â€”163,1967. eases. However, the vacuoles examined by us in the electron 4. BÃ¼ttner, D. W., and Horstmann, E. Das Sphaeridion, Eine microscope were predominantly cytoplasmic. That these vac Weit Verbreitete Differenziemung des Karyoplasma. Z. Zell uoles had no continuity with the extracellular matrix was forsch. Mikroskop. Anat. Abt. Histochem., 77: 589-605, 1967.

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5. Cancilla, P., Morecki, R., and Hurwitt, E. S. Fine Structure 20. Horwitz, T. Chordal Ectopia and Its Possible Relation to of a Recurrent Chordoma. Arch. Neurol., 11: 289â€”295,1964. Chordoma. Arch. Pathol., 31: 354â€”362,1941. 6. Cappell, D. F. Chordoma of the Vertebral Column with Three 21. Jones, A. L., and Fawcett, D. W. Hypertrophy of the Agranu New Cases. J. Pathol. Bacteriol., 31 : 797â€”814,1928. lar Endoplasmic Reticulum in Hamster Liver Induced by 7. Caulfield, J. B. Effects of Varying the Vehicle for 0504 in Tis Phenobarbital (With a Review on the Functions of This Or sue Fixation. J. Biophys. Biochem. Cytol., 5: 827â€”830,1957. gane!!e in Liver) . J. Histochem. Cytochem., 14: 215â€”232,1966. 8. Claude, A. Mitochondrial Cristae During Liver Regeneration. 22. Novikoff, A. B., Essner, E., and Quintana, N. Golgi Apparatus Protoplasma, 68: 275â€”282,1967. and Lysosomes. Federation Proc., 23: 1010â€”1022,1964. 9. Crawford, T. The Staining Reactions of Chordoma. J. Clin. 23. Novilcoff, A. B., and Shin, W. Y. The Endoplasmic Reticulum Pathol., 11: 110â€”113,1958. in the Golgi Zone and Its Relations to Microbodies, Golgi 10. Dahlin, D. C., and MacCarty, C. S. Chordoma; A study of 59 Apparatus and Autophagic Vacuoles in Rat Liver Cells. J. Cases. Cancer, 5: 1170â€”1178,1952. Microscopie, 5: 187â€”206,1964. 11. Erlandson, R. A. A New Maraglas, D. E. R. 732, Embedment 24. Palade, G. E. A Study of Fixation for Electron Microscopy. for Electron Microscopy. J. Cell Biol., 22: 704â€”709,1964. J. Exptl. Med., 95: 285â€”298,1952. 12. Evans, R. W. Histological Appearances of Tumors, pp. 151â€”163. 25. Pendergrass, E. P., Schaeffer, J. P., and Hodes, P. J. The Head Baltimore : Williams & Wilkins Co., 1966. and Neck in Roentgen Diagnosis, Ed. 2, pp. 989-993. Spring 13. Fawcett, D. W. The Cell : Its Organelles and Inclusions. Phil field, Ill. : Charles C Thomas, 1956. adelphia: W. B. Saunders Co., 1966. 26. Reynolds, E. S. The Use of Lead Citrate at High pH as an 14. Fletcher, E. M., Waltman, H. W., and Adson, A. W. Sacrococ Electron-Opaque Stain in Electron Microscopy. J. Cell Biol., cygeal Chordomas ; A Clinical and Pathologic Study. Arch. 17: 208â€”212,1963. Neurol. Psychiat., 33: 283â€”299,1935. 27. Ribbert, H. Geschwu!st!ehre fÃ¼rArzte and Studirende. pp. 149â€” 15. Friedmann, I., Harrison, D. F. N., and Bird, E. S. The Fine 152.Bonn: F. Cohen,1904. Structure of Chordoma with Particular Reference to the Phys 28. Sandborn, E., Koen, P. F., McNabb, J. D., and Moore, G. aliphorous Cell. J. Clin. Pathol., 15: 116â€”125,1962. Cytoplasmic Microtubules in Mammalian Cells. J. Ultrastruct. 16. Fukuda, S., Eguchi, G., and Takeuchi, S. Histological and Res., 11: 123â€”138,1964. Electron Microscopical Studies on Sexual Differences in Struc 29. Spjut, H. J., and Luse, S. A. Chordoma: An Electron Micro ture of the Corpora Allata of the Silkworm, Bombyx mon. scopic Study. Cancer, 17: 643-656, 1964. Embryologia, 9: 123â€”158,1966. 17. Gentil, F., and Coley, B. L. Sacrococcygeal Chordoma. Ann. 30. Stempak, J. G., and Ward, R. T. An Improved Staining Surg., 127: 432-455, 1948. Method for Electron Microscopy. J. Cell Biol., 22: 697â€”701, 18. Hertig, A. T., and Adams, E. C. Studies on the Human Oocyte 1964. and Its Follicle. I. Ultrastructural and Histochemical Observa 31. Stewart, M. J., and Morin, J. E. Chordoma: A Review with tions on the Primordial Follicle Stage. J. Cell Biol., 34: 647â€” Report of a New Sacrococcygeal Case. J. Patho!. Bacteriol., 675, 1967. 29: 41â€”60,1926. 19. Higinbotham, N. L., Phillips, R. F., Farr, H. W., and Hustu, 32. Utne, J. R., and Pugh, D. G. The Roentgenologic Aspects of H. 0. Chordorna-: Thirty-Five Year Study at Memorial Hospi Chordoma. Am. J. Roentgeno!. Radium Therapy Nuc!. Med., tje.!. Cancer, 20: 1841â€”1856,1967. 74: 593-608, 1955.

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Figs. 1â€”5are light micrographs. Figs. 1 and 2 are of paraffin-embedded material, while Figs. 3â€”5are of half-micron-thick sections of epoxy-embedded tissue. Fig. 1. An area of tumor showing strands of vacuolated physaliferous cells and small stellate cells separated by large areas of in tracel!ular matrix. H & E, X 120. Fig. 2. Typical tumor cells embedded in a dense, collagenous matrix. H & E, x 120. Fig. 3. This section shows physaliferous cells displaying varying degrees of vacuolization. Some are of the â€œsignet-ringâ€•type,with the nucleus and cytoplasm displaced to the cell periphery by a large vacuole (arrows) . The stel!ate cells are smaller and have a denser cytoplasm. The cells are stained various shades of blue, while the matrix is stained pink. Toluidine blue, X 400. Fig. 4. A higher power micrograph showing numerous intracellular vacuoles, some of which contain flocculent material (Vi) . The difference in staining between the clear vacuoles (V2) and the intercellular matrix is obvious. Note the small vacuoles in the stellate cell at the upper right. Toluidine blue, X 1350. Fig. 5. Two types of nuclear inclusions are present in this bibbed nucleus. One type is a transversely sectioned process of cyto plasm, thus constituting a pseudoinclusion (P1). In this connection, note the deep clefts in the nuclear membrane of the larger lobe. Two true intranuclear inclusions (INI) are demarcated by a halo of low density. The darkly stained nuclear structures are nucleoli. The adjoining cell contains a large vacuole (V) filled with flocculent material. The dense structures (@) in the cytoplasm are mito chondrial endoplasmic reticulum complexes. Toluidine blue, X 1880. Figs. 6â€”16are electron micrographs of thin sections stained serially with umanyl acetate and lead citrate. Fig. 6. Survey micrograph of chordoma cells. A physaliferous cell containing a huge vacuole (V) is at the upper left. The other cells are of the stellate type. They are characterized by a highly filamentous cytoplasm and by a relative paucity of vacuoles. At the right is a series of cell processes, each of which is enwrapped by other cells. This cellular interdigitation is common among all types of chordoma cells. Clusters of glycogen are distributed throughout the cytoplasm, being especially prominent in the cell process at the upper right. x 7,500. Fig. 7. A cytoplasmic process surrounded by portions of two other cells and bound to them by small desmosomes (D). The proc ess contains numerous filaments (F) , which appear as dots or granules in transverse section. The surrounding cells have abundant smooth endoplasmic reticulum (SER). x 24,000. Fig. 8. A nucleus demonstrating two types of nuclear inclusions. The large central vacuole appears to be within the nucleus but actually is contained in a cytoplasmic extension, here seen in cross-section. A narrow rim of cytoplasm that includes a mitochondrion (arrow) envelops the vacuole. The cytoplasmic process is demarcated by nuclear envelope (E) with associated condensed chromatin. A similar process (*), also in transverse-section but without vacuoles, is seen at the upper left. A true intranuclear inclusion (NB) of the nuclear body type is present at the lower right of the nucleus. NU, nucleolus. X 11,000. Fig. 9. A nucleus displaying many pseudoinclusions, some of which contain cytoplasmic vacuoles. X 21,000. Fig. 10. A group of true intranuclear inclusions. These usually are clear vacuoles with a single limiting membrane. Unlike the pseudoinclusions, no chromatin is condensed at their periphery. A nucleolus is at the lower right. x 21,600. Fig. 11. A typical mitochondria! endoplasmic reticulum complex. The regular alternation of organelles is well demonstrated. The mitochondria are attenuated in their central regions and bulbous at their ends. Elements of smooth endoplasmic reticulum and Golgi complex are present in the cytoplasm. Small clusters of glycogen are scattered through the cytoplasm, and a deposit of this substance is present in a vacuole (arrow). A portion of the nucleus is at the left. X 59,000. Fig. 12. Distended endoplasmic reticulum cisternae with associated mitochondria. Note that ribosomes are present on the cistemnal membranes primarily where mitochondria are closely apposed to the membrane. X 50,000. Fig. 13. A mitochondrial endop!asmic reticulum complex in a region rich in smooth endoplasmic reticulum. Note the transition of rough into smooth endoplasmic reticulum at the periphery of the complex (arrow). This area is shown at higher magnification in the next micrograph. x 33,000. Fig. 14. An enlarged portion of Fig. 13, showing the direct continuity of rough endoplasmic reticulum and smooth endoplasmic reticulum. X 48,000. Fig. 15. A Golgi complex displaying the fenestrated appearance typical of this organel!e in chordoma cells. A cytoplasmic vacuole is present at the top of the micrograph. x 44,000. Fig. 16. A grazing section of a fenestrated Golgi cistern. Several vesicles appear to be in continuity with the Golgi membrane (arrow). X 55,000.

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OCTOBER 1968 2125

Robert A. Erlandson, Bernard Tandler, Philip H. Lieberman, et al.

Cancer Res 1968;28:2115-2125.

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