Dictionary
Mario P. Iturralde in Dictionary and Handbook of Nuclear Medicine and Clinical Imaging, 1990
Bone. Bone consists of an organic component, the bone matrix, and a crystalline inorganic component, hydroxyapatite, It also contains an appreciable amount of water. The most important constituents of the matrix are the collagen fibers surrounded by amorphous ground substances of mucoproteins and mucopolysaccharides. Reticulin fibers are also present. Upon or within the collagen fibers are laid down the hydroxyapatite crystals that give to bone its characteristic hardness. Bones grow rapidly throughout childhood and adolescence both in length and to some extent in thickness, but even in maturity small areas of bone are constantly being removed and replaced. Apposition and resorption are continuous throughout life. Apposition takes place through the activity of a cell, the osteoblast, which first of all appears to lay down the ground substance and collagen fibers which subsequently become calcified. Resorption takes place through the activity of another cell, the osteoclast, which removes both the apatite and the matrix, simultaneously releasing them to the bloodstream.
Introduction to Myeloproliferative Neoplasms
Wojciech Gorczyca in Atlas of Differential Diagnosis in Neoplastic Hematopathology, 2014
The BM cellularity and proportion of different lineages are best evaluated on the core biopsy. BM cellularity decreases with age; on average, the expected (normal) cellularity corresponds to 100 – patient age (e.g., 50-year-old person shows 50% BM cellularity, whereas 70-year-old person shows 30% BM cellularity). BM cellularity is usually increased with either panmyelosis or hyperplasia of one or two myeloid lineages. Myeloid hyperplasia may be accompanied by a leftward shift and accentuated paratrabecular myeloid immaturity. Megakaryocytes are increased and display atypia and often clustering. Megakaryocytic clustering generally correlates with an increase in reticulin fibers. Hypolobated micromegakaryocytes are more typical for CML, whereas giant and bizarre forms of megakaryocytes are more often seen in PMF and to a lesser degree in PV. ET shows large and mature megakaryocytes with hyperlobated staghorn nuclei. Both CMML and JMML require ≥1 × 109/L monocytes in the blood for the diagnosis. Reticulin fibers are variably increased. Fibrosis is most pronounced in PMF and in the late (fibrotic) stage of other MPNs. Sinuses may be dilated with intravascular hematopoiesis and accompanying extramedullary hematopoiesis. BM fibrosis may also accompany CML, mastocytosis, and PV. ET usually does not show reticulin fibrosis (if present, it is minimal and focal). In addition to thrombotic, infectious, and hemorrhagic complications, MPN may progress to acute leukemia (blast phase or crisis).
Role of Autoimmunity in Gluten-Sensitive Enteropathy
Tadeusz P. Chorzelski, Ernst H. Beutner, Vijay Kumar, Tadeusz K. Zalewski in Serologic Diagnosis of Celiac Disease, 2020
Some understanding of the pathogenic significance of IgA-EmA derives from the nature and distribution of the antigens with which they react. Morphologically, their structure is that of extracellular matrix components formed by smooth muscle cells. They lie on and between the myofibrils55 (see Chapter 7 for illustration). The most reactive forms in normal tissue occur in the smooth muscle fibers close to lymphoid tissue or epithelium of the gastrointestinal tract, spleen, lymph nodes, or thymus. The IgA-EmA antigen appears to be synthesized by smooth muscle myocytes and is apparently modulated by their proximity to lymphoid cells, as demonstrated by their organ specificity.55 That is, they give maximal reactivity with selected smooth muscles, lymphoid tissue, and spleen. The role of the proximity of the gastrointestinal tract epithelium or lymphoid tissue is well illustrated by the observations that while smooth muscles of arteries in distal areas are either very weakly reactive or essentially nonreactive with IgA-EmA, arteries in the skeletal muscle of the upper third of the esophagus (which has no smooth muscle layers) are strongly reactive (Figure 1). This example of the interrelationship between the arterial smooth muscle matrix components and surrounding cellular elements illustrates the long-recognized interrelationships of cells to reticulin.50 (Reticulin refers to the morphological structure of some insoluble matrix components.)
Pathologic and Immunophenotypic Characterization of Syncytial Giant Cell Variant of Pediatric Hepatocellular Carcinoma. A Distinct Subtype
Published in Fetal and Pediatric Pathology, 2023
Mukul Vij, Jagadeesh Menon, Komalavalli Subbiah, Lexmi Priya Raju, Gowripriya Gowrisankar, Naresh Shanmugum, Ilankumaran Kaliamoorthy, Ashwin Rammohan, Mohamed Rela
The explanted liver showed greenish discoloration and had multiple distinct whitish nodules ranging in sizes from 0.1 cm to 1.2 cm (Fig. 4B). Segment 5 shows an encapsulated distinct white nodule corresponding to the neoplastic lesion reported on imaging. Microscopy demonstrated distorted lobular architecture with micronodular cirrhotic transformation (Fig. 4C). Macroregenerative nodules were noted. There was variable portal inflammation, prominent portal/periportal cholangiolar proliferation with ductular bile plugs, and lobular bilirubinostasis. Diffuse sinusoidal fibrosis was highlighted by the trichrome stain (Fig. 4D). A single tumor nodule measuring 6 mm with neoplastic cells arranged in sheets and displaying clear cytoplasm was identified (Fig. 4E). Diffuse syncytial giant cell transformation containing 4 to 25 nuclei was also noted. Cholestasis and hemopoiesis was observed. There was no vascular or perineural invasion. Reticulin was decreased.
Autoimmune myelofibrosis associated with systemic lupus erythematosus: a case report
Published in Modern Rheumatology Case Reports, 2020
Tansri Wibowo, Shoji Kawada, Yutaka Ishida, Yuko Yoshimine, Nachi Ishikawa, Keisuke Kawamoto, Yasuhiro Kato, Shinji Higa, Atsushi Ogata, Keiji Maeda
MF is characterised by the increased deposition of reticulin fibres and, in some cases, collagen fibres [3]. It is characterised by clonal proliferation of myeloid stem cells accompanied by stromal production of fibrinous ground substance. The exact pathogenesis of MF is not fully understood. The increased expression of inflammatory cytokines, transforming growth factor-β, impaired megakaryocyte function, and aberrant JAK-STAT signalling have all been implicated in the pathogenesis of fibrogenesis. Increased fibrosis in bone marrow might contribute to a disorganised bone marrow microenvironment and might impair haematopoiesis. Although MF is seen in a variety of malignant and non-malignant diseases, bone marrow fibrosis was thought to be an adverse prognostic variable in myeloproliferative diseases. In contrast, AIMF, associated with autoimmune diseases, especially SLE, generally has a favourable prognosis. In SLE-associated AIMF, epidemiological, clinical, and biological features of lupus were unremarkable and bone marrow findings also proved highly variable, except for reticulin fibrosis. The clinical features of SLE-associated AIMF are summarised in Table 2 [2,9–39].
β-catenin and PPAR-γ levels in bone marrow of myeloproliferative neoplasm: an immunohistochemical and ultrastructural study
Published in Ultrastructural Pathology, 2018
Tijana Subotički, Olivera Mitrović Ajtić, Mileva Mićić, Tamara Kravić Stevović, Dragoslava Đikić, Miloš Diklić, Danijela Leković, Mirjana Gotić, Vladan P. Čokić
Myeloproliferative neoplasms (MPNs), including polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF), are clonal bone marrow stem cell disorders characterized by a proliferation of one or more of the myeloid, erythroid or megakaryocytic cell lines. This proliferation results in increased numbers of granulocytes, erythrocytes or platelets in the peripheral blood. The bone marrow of PV patients displays panmyelosis and therefore an increase in cellularity with slightly increased reticulin fibrosis.1 The presence of reticulin is extremely rare in ET patients and very few patients (<10%) develop myelofibrosis, known as post-ET myelofibrosis.2 PMF is described by bone marrow fibrosis and extramedullary hematopoiesis. The clonal proliferation of hematopoietic stem cells produces growth factors leading to fibrosis of the bone marrow. Initially, the bone marrow is a hypercellular, but normal hematopoiesis is diminished as the bone marrow becomes fibrotic and patients become pancytopenic.3
Related Knowledge Centers
- Basement Membrane
- Collagen
- Reticular Cell
- Lymphatic System
- Bone Marrow
- Connective Tissue
- Liver
- Carbohydrate
- Collagen, Type Iii, Alpha 1
- Silver Staining