Ultrastructural Studies on Monocytic Leukaemia

Abstract

Bone marrow specimens from four cases of pure monocytic leukaemia (Schilling type) and three cases of myelo-monocytic leukaemia (Naegeli type) were examined by electron microscopy. The hallmark of the monoblasts and more mature monocytoid forms was the extreme nuclear irregularity with frequent nuclear bridges and blebs. Abundant cytoplasm with a serrated margin, dense granules, numerous pinocytic vesicles and vacuoles, frequent peri-nuclear fibrillar bands and a well-developed Golgi zone served as additional criteria for identifjring monoblasts. Various stages in the maturation of monoblasts were observed. Stem cells possessed a large round nucleus which became extremely folded with increasing maturity. The gradual appearance of condensed chromatin paralleled this nuclear polymorphism. The fine structure of these monoblasts was compared with that of myeloblasts to point out distinguishing features. It is felt that ultrastructural analysis can be of value in separating pure monocytic leukaemia from myelo-monocytic leukaemia.Reschad & Schilling-Torgau (1913) first described monocytic leukaemia. Downey later separated monocytic leukaemia into two types-a pure monocytic leukaemia which he termed Schilling typeand a mixed myelo-monocytic which he termed Naegeli type (Downey, 1938; Watkins & Hall, 1940). The diagnosis of monocytic leukaemia is based on the presence of large numbers of monocytoid as well as related blast forms. In the pure form, these comprise over 60% of the white blood cells (Wintrobe, 1967;Clough, 1932). At present, despite special stains, there is occasional difficulty with light microscopy in differentiating pure monocytic from myelo-monocytic leukaemia. In fact, some maintain that the true incidence of pure monocytic leukaemia is much higher than usually reported, due to misdiagnosis as myelo-monocytic leukaemia (Osgood, 1969).To date, there have only been fragmentary reports on the ultrastructure of monocytic leukaemia (Freeman

Hairy Cell Leukemia (‘Leukemic Reticuloendotheliosis’), Reticulosarcoma, and Monocytic Leukemia

“…Besides some large granules, 0.5-0.8 //m in diameter, most cytoplasmic granules are distinctly smaller, 0.1-0.2 //m in diameter, electron-dense, occasionally comma-shaped. Bundles of fibrils occur as well as phagocytosis of degenerat ed thrombocytes and erythrocytes [15,27],…”

“…These peculiar features unequivocally distinguish monocytes from other hematopoietic or blood cells. Furthermore, monocytic leukemia has been studied with the same techniques, and their close relationship to normal monocytes and their physiological precursors has been proved [4,15,25,27,33,52,56],…”

High Risk Subgroup of Acute Myelomonocytic Leukemia (AMML) with Orbito-Ocular Granulocytic Sarcoma (OOGS) in Turkish Children

“…The hematologic picture by light and electron microscopic studies could not be distinguished from those observed in AMML cases without OOGS. Ultrastructural examination of the tumor cells can also contribute to a definitive diagno sis of GS as is the case in our study [3,7,10,13,19],…”

Acute Monocytic Leukemia in an Irradiated Beagle

“…In human and canine myeloproliferative disorders, there are occasional difficulties in differentiating pure monocytic leukemia from the myelomonocytic type based on Wright-Giemsa staining alone [6,171. In acute leukemias of man, a correct differential diagnosis usually can be made with Sudan black, peroxidase and PAS staining as well as naphthol-AS-D acetate esterase, with and without sodium fluoride.…”