Classification Approximately 20 different groups of sarcomas are recognized on the basis of the pattern of differentiation toward normal tissue. For example, rhabdomyosarcoma shows evidence of skeletal muscle fibers with cross-striations; leiomyosarcomas contain interlacing fascicles of spindle cells resembling smooth muscle; and liposarcomas contain adipocytes. When precise characterization of the group is not possible, the tumors are called unclassified sarcomas. All of the primary bone sarcomas can also arise from soft tissues (e.g., extraskeletal osteosarcoma).
Epidemiology Idiopathic MDS is a disease of the elderly; the mean age at onset is 68 years. There is a slight male preponderance. MDS is a relatively common form of bone marrow failure, with reported incidence rates of 35 to 100 per million persons in the general population and 120 to 500 per million in the elderly. MDS is rare in children, but monocytic leukemia can be seen.
Therapy-related MDS is not age-related and may occur in as many as 15% of patients within a decade following intensive combined modality treatment for cancer. Rates of MDS have increased over time,...
Pathophysiology Bone marrow failure results from severe damage to the hematopoietic cell compartment. In aplastic anemia, replacement of the bone marrow by fat is apparent in the morphology of the biopsy specimen (Fig. 102-1) and MRI of the spine. Cells bearing the CD34 antigen, a marker of early hematopoietic cells, are greatly diminished, and in functional studies, committed and primitive progenitor cells are virtually absent; in vitro assays have suggested that the stem cell pool is reduced to ≤1% of normal in severe disease at the time of presentation.
Bone Marrow The bone marrow is usually normal or hypercellular, but in 20% of cases it is sufficiently hypocellular to be confused with aplasia. No single characteristic feature of marrow morphology distinguishes MDS, but the following are commonly observed: dyserythropoietic changes (especially nuclear abnormalities) and ringed sideroblasts in the erythroid lineage; hypogranulation and hyposegmentation in granulocytic precursors, with an increase in myeloblasts; and megakaryocytes showing reduced numbers or disorganized nuclei.
Incidence and Epidemiology
Bone sarcomas are rarer than soft tissue sarcomas; they accounted for only 0.2% of all new malignancies and 2370 new cases in the United States in 2007. Several benign bone lesions have the potential for malignant transformation. Enchondromas and osteochondromas can transform into chondrosarcoma; fibrous dysplasia, bone infarcts, and Paget's disease of bone can transform into either malignant fibrous histiocytoma or osteosarcoma.
G1,2 low grade
G1,2 low grade
Stage IVA T
Stage IVB T
Any T N
Osteosarcoma, accounting for almost 45% of all bone sarcomas, is a spindle cell neoplasm that produces osteoid (unmineralized bone) or bone.
Chondrosarcoma Chondrosarcoma, which constitutes ~20–25% of all bone sarcomas, is a tumor of adulthood and old age with a peak incidence in the fourth to sixth decades of life. It has a predilection for the flat bones, especially the shoulder and pelvic girdles, but can also affect the diaphyseal portions of long bones. Chondrosarcomas can arise de novo or as a malignant transformation of an enchondroma or, rarely, of the cartilaginous cap of an osteochondroma. Chondrosarcomas have an indolent natural history and typically present as pain and swelling.
Cancer in the bone may produce osteolysis, osteogenesis, or both. Osteolytic lesions result when the tumor produces substances that can directly elicit bone resorption (vitamin D–like steroids, prostaglandins, or parathyroid hormone–related peptide) or cytokines that can induce the formation of osteoclasts (interleukin 1 and tumor necrosis factor). Osteoblastic lesions result when the tumor produces cytokines that activate osteoblasts. In general, purely osteolytic lesions are best detected by plain radiography, but they may not be apparent until they are 1 cm.
Myelodysplasia, and Related Bone Marrow Failure Syndromes
Aplastic Anemia, Myelodysplasia, and Related Bone Marrow Failure Syndromes: Introduction
macrocytic and are characterized by a low reticulocyte count. Deficient production of RBCs occurs with marrow damage and dysfunction, which may be secondary to infection, inflammation, and cancer.
Aplastic anemia is pancytopenia with bone marrow hypocellularity. Acquired aplastic anemia is distinguished from iatrogenic marrow aplasia, marrow hypocellularity after intensive cytotoxic chemotherapy for cancer. Aplastic anemia can also be constitutional: the genetic diseases Fanconi's anemia and dyskeratosis congenita, while frequently associated with typical physical anomalies and the development of pancytopenia early in life, can also present as marrow failure in normal-appearing adults.
Immune-Mediated Injury The recovery of marrow function in some patients prepared for bone marrow transplantation with antilymphocyte globulin (ALG) first suggested that aplastic anemia might be immune-mediated. Consistent with this hypothesis was the frequent failure of simple bone marrow transplantation from a syngeneic twin, without conditioning cytotoxic chemotherapy, which also argued both against simple stem cell absence as the cause and for the presence of a host factor producing marrow failure.
Laboratory data support an important role for the immune system in aplastic anemia.
Definition and Differential Diagnosis PRCA is characterized by anemia, reticulocytopenia, and absent or rare erythroid precursor cells in the bone marrow. The classification of PRCA is shown in Table 102-4. In adults, PRCA is acquired. An identical syndrome can occur constitutionally: Diamond-Blackfan anemia, or congenital PRCA, is diagnosed at birth or in early childhood and often responds to glucocorticoid treatment; a minority of patients have etiologic mutations in a ribosomal RNA processing gene called RPS19.
history began more than 100 years ago. In the field of dentistry, crude devices
by today' s standards were developed in the late 19th century to evaluate the density
of the bone in the mandible. The advances in technology continued, albeit slowly,
for the first half of the 20th century, gaining some speed in the 1960s and 1970s.
The introduction of dual-energy X-ray absorptiometry in the late 1980s truly
opened the door to clinicians' offices for bone densitometry.
A thought-provoking book about the future of bone and joint disorders. This is the Decade of Bone and Joint, a time where rapid developments in our understanding of these disorders contend with massive increases in these chronic conditions throughout the world. By drawing on current knowledge and expertise, the book considers future scenarios such as the development of scientific theories, technology, prevention, diagnosis and treatment.
Studies on quantitative fit analysis of precontoured fracture fixation plates emerged within the last few years and therefore, there is a wide research gap in this area. Quantitative fit assessment facilitates the measure of the gap between a fracture fixation plate and the underlying bone, and specifies the required plate fit criteria. For clinicallymeaningful fit assessment outcome, it is necessary to establish the appropriate criteria and parameter.
This book will change the way you think about bone density and
osteoporosis. The weakening of bones is often viewed as a calcium
defi ciency, when actually it’s an imbalance between calcium intake
As nutrition professor Amy Joy Lanou, Ph.D., and noted medical
journalist Michael Castleman eloquently reveal, diets rich in animal
protein, including meat and dairy, add acid to the blood. This acid
accelerates osteoporosis by depleting bones of calcium, phosphorus,
Lecture Human anatomy and physiology - Chapter 6: Bones and skeletal tissues (part a). When you finish this chapter, you should: Describe the functional properties of the three types of cartilage tissue, locate the major cartilages of the adult skeleton, explain how cartilage grows, name the major regions of the skeleton and describe their relative functions, compare and contrast the four bone classes and provide examples of each class,...
Chapter 6: Bones and skeletal tissues (part b) provides knowledge of bone development, bone homeostasis, homeostatic imbalances of bone and developmental aspects of bones. After completing this chapter, students will be able to: Compare and contrast intramembranous ossification and endochondral ossification, describe the process of long bone growth that occurs at the epiphyseal plates,...and other contents.