Scand J Haematol(l982) 29,250-256

CASE REPORT

Ultrastructural Aspects of Leukaemic Cells in Acute Myeloblastic Leukaemia

ANDRZEJ NOWAKOWSKI, JANINA HALLIOP & JERZY S. TARACH

Clinic of Haematology, Institute of Internal Medicine, Medical Academy and

Department of Electron Microscopy, Medical Academy, Lublin, Poland

Ultrastructural aspects of leukaemic cells in a case of myeloblastic leukaemia are described. Changes concerning of mitochondria1 ultrastructure, but primarily the presence of vast numbers of fibrillar structures in the cytoplasm of the examined cells were observed. These structures were spreading through their gradual widening to cover almost the whole cell cytoplasm, damaging its organellae and internal architecture. The nature of the observed changes remains unknown.

Key words: acute rnyeloblastic leukaemia - electron microscopy - fibrillar structures - leukaemic cells

Accepted for publication February 28, 1982

Correspondence to: Dr. Andrzej Nowakowski, Clinic of Haematology, Institute of Internal Medicine, Medical Academy, 20-090 Lublin, Jaczewskiego 8, Poland

Characterisation of the leukaemic cells may be significant not only in the prognosis it- self, but also in the treatment. As a rule we now apply cytochemical diagnostics to the investigation of leukaemic blasts. However, since it often fails to give a univocal answer, special techniques, like electron micro- scopy, should therefore be applied. Elec- tronmicroscopic examinations of acute leukaemic myeloblasts reveal a number of pictures not seen before, not easily yielding to interpretation (Huhn & Borchers 1968, Hayhoe & Cawley 1972, Schumacher et a1 1972, 1973, Bessis 1973, Cawley & Hayhoe 1973, Micu & Ruzicka 1975, Stenstam et a1 1975, Stavem et a1 1977).

We observed a case of acute myeloblastic leukaemia where the blastic cells showed

typical cytochernical features, but where light microscopy revealed the presence of forms other than Auer rods in their cyto- plasm. Electron microscopy was used to probe the nature of the observed changes in the blastic cells.

CASE REPORT

A 51-year-old woman was admitted in April 1980 because of genital bleeding, ecchymoses, suggillations, fever up to 39°C and pain in the limbs. Physical examination showed hepatosplenomegaly.

Laboratory examinations: ESR 115 mm/l h, Hb 4.96 mmol/l, RBC 2.7 x 101*/1, WBC 132 x 109/1 with paramyeloblasts 98 %, platelets 68.2 x lOg/l.

The bone marrow was hypercellular consisting of 98 % typical paramyeloblasts with high activity of

0036-.553X/82/08025(M7 $02.50/0 0 1982 Munksgaard, Copenhagen

ULTRASTRUCTURE OF AML CELLS 25 1

peroxidase but without PAS-positive substance. Our attention was drawn to the presence of pink spherical inclusion bodies in the cytoplasm. These were not Auer rods since they did not exhibit peroxidase ac- tivity. They usually gathered around the cell nucleus and, in cells with a slightly concave nucleus, in its convexity. The prothrombin time was prolonged to 20 s.

There was a slight proteinuria, but normal urinary sediment and normal renal function.

The patient received combination chemotherapy. On the second day of treatment, CNS haemorrhage sud- denly occurred and the patient died on the 5th d in the clinic. Autopsy showed: spleen weight 470 g, liver weight 2 500 g, several cerebral haemorrhagic and leukaemic foci.

MATERIAL AND METHOD

Examinations of bone marrow and peripheral blastic cells were performed. The material was fixed in cold 3 % glutaraldehyde in 0.1 mol/l cacodylate buffer, pH 7.4, with 1 % addition of saccharose for 1 h and then postfixed in 1% osmium tetroxide in 0.1 mol/l ca- codylate buffer, pH 7.4, according to the method de- scribed by Latalski et al (1976). After dehydration, the material was embedded in Epon 812. Ultrathin sections were obtained with Tesla BS 490 ultramicrotome and then examined and photographed with Tesla BS 613 electron microscope.

RESULTS

The blastic cells were predominantly round in shape with a very small number of cyto- plasmic ledges. They had, however, large nuclei. Blast nuclei had a round or oval shape with a small irregularity in more mature cells. Undulating nucleus membrane had irregularities directed inward towards the karyoplasm. Nucleus chromatin was spread evenly. Marginal chromatin concentrations, typical for more mature cells, were not observed within the karyoplasm. In some blastic cells a clear nucleolus could be seen, in most of them we could also observe a

widening of the space between nuclear membranes.

In the blast cytoplasm, we observed round or oval mitochondria, ribosomes (both those lying loosely and those attached to mem- branes) and the channels of smooth endo- plasmic reticulum (SER). Neither the Golgi structures nor granules were observed. In the basic cytoplasm of all the cells there occurred numerous fibrillar structures spread within its entirity or grouped most often near the cell nucleus (Figure 1).

Among the disorderly spread fibrillar structures, one could see normal mito- chondria as well as the membranes of endo- plasrnic reticulum. In some blastic cells these structures were seen to come closer to the cell nucleus, to concentrate and con- solidate into strands of fibrillar substance which had no organellae inside. Then, the fibrillar structures were pushing the re- maining organellae towards the nucleus and encircling them (Figure 1).

A later phase in the development of this process is the situation when - inside the circular strand of fibrillar structures - cyto- plasmic organellae occur among which there are: mitochondria with a disturbed system of cristae, widened channels of SER and RER (rough endoplasmic reticulum) as well as electron-dense concentrations of granular and membranous material (Figures 1, 2). Inside mitochondria we could also observe the presence of bright areas be- tween the damaged cristae mitochondriales (Figure 2). We did not notice virus-like particles but we observed small electron dense bodies (Figure 3). In some blastic cells fibrillar structures surrounded electron dense amorphic material, within which there were no identifiable subcellular struc- tures (Figure 2).

252 NOWAKOWSKI, HALLIOP & TARACH

Figure 1. Leukaemic myeloblast. N = nucleus, M = mitochondrium, F = fibrillar structure, ER = endoplasmic reticulum ( X 42000).

ULTRASTRUCTURE OF AML CELLS 253

Figure 2. Leukaemic myeloblast. N = nucleus, M = mitochondrium, F = fibrillar structure, AM = amorphic material ( x 42000).

254 NOWAKOWSKI, HALLIOP & TARACH

Figure 3. Leukaemic rnyeloblast. N = nucleus, M = mitochondrium, F = fibrillar structure, DB = dense bodies ( x 25000).

ULTRASTRUCTURE OF AML CELLS 255

DISCUSSION

Electron microscopy of leukaemic myelo- blasts reveals a number of interesting dis- turbances of their ultrastructure. Both in the case of normal (Huhn & Stich 1969, Cawley & Hayhoe 1973) and leukaemic myeloblasts (Hayhoe & Cawley 1972, Schu- macher et a1 1972, 1973, Cawley & Hayhoe 1973) there have been reports on the pres- ence of single myelin and fibrillar structures and even, as in the latter case, fibres form- ing into strands, but we have not come across reports describing of such an ac- cumulation of fibrillar structures as those found by us anywhere in the available litera- ture.

Somewhat similar observations to ours, though referring to plasmocytes, were re- ported by Ogawa et al (1976). These authors identified vast numbers of fibrillar structures localized intracellularly with amyloid fibres. In our case there were no grounds for considering the amyloid fibres to be the primary or secondary cause of the observed changes. On the other hand, we wondered if they could be peculiar forms of Auer rods. However, on the basis of the outer appear- ance of these changes, and our observations of their gradual development, we came to the conclusion that they are peculiar dis- turbances of the ultrastructure of leukaemic cells in the form of such an accumulation of fibrillar substance.

In agreement with the reports of Shira- hama & Cohen (1967) and Zucker-Franklin & Franklin (1970) these changes did not have amyloid nature and moreover, they were not Auer rods (Huhn & Borchers 1968). It seems that they are not widened RER channels which, as Stavem et a1 (1977) suggest, are the initial form of Auer rods,

since we observed them inside the described fibrillar structures.

On the basis of the observed changes in the examined leukaemic myeloblasts one could attempt a classification of the order of appearance and the increase of the patho- logical changes producing fibrillar struc- tures. Thus, in the initial phase of their formation the system of these structures would lie disorderly among cytoplasmic or- ganellae, then they would take an ordered form and condense into strands, thus push- ing cytoplasmic organellae towards the cell nucleus and finally with a strand, encircling and closing the circularly running fibres of the already pathologically changed organel- lae. In the final phase of these changes is perhaps formed amorphic and electron dense material, difficult to identify.

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256 NOWAKOWSKI, HALLIOP & TARACH

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