Radiographic appearance and CT
Conventional radiography remains the primary imaging modality for myelofibrosis. The main radiological sign detected in a significant proportion of patients is osteosclerosis (bone sclerosis). Changes in bone density are predominantly diffuse, although sometimes sclerosis may be patchy, focal (patchy).
The most typical localization of the pathological process is the axial skeleton (axial skeleton) and the metaphyseal regions of long bones. The pathogenesis of sclerosis development is associated with the active formation of new endosteal and trabecular bone tissue. As a result of this process, a narrowing of the medullary canal lumen naturally occurs (reduced marrow diameter). Computed tomography (CT) allows a detailed assessment of these structural changes, demonstrating marked trabecular thickening leading to dense sclerosis.
When the disease progresses to the advanced stage, radiograms show radiolucent areas (lucent areas) caused by the reactive proliferation of fibrous tissue. Periosteal reaction is recorded in approximately one-third of cases. The favored localization of periostitis is the medial surface of the distal femur (distal femur) and the proximal tibia (proximal tibia). A mixed pattern combining sclerotic and lytic foci may be observed in the skull bones.
Magnetic resonance imaging (MRI) and scintigraphy
Magnetic resonance imaging (MRI) has high soft-tissue contrast in assessing bone marrow status. A typical radiological pattern of myelofibrosis on MRI consists of a marked decrease in signal intensity.
- Diffuse or heterogeneous hypointensity is observed.
- The signal decrease is clearly visible on both T1-weighted and T2-weighted images (T1 and T2 weighted sequences), including spin-echo (SE) and fast spin-echo (FSE) sequences.
MRI is crucial for assessing dynamics: the method allows visualization of the restoration (regression) of normal bone marrow signal following successful allogeneic stem cell transplantation.
Bone scintigraphy (bone scintigraphy) is used as part of radionuclide diagnostics. In severe involvement, it may demonstrate the characteristic "superscan" pattern ('superscan').
Clinical course, prognosis, and complications
Myelofibrosis is characterized by an extremely serious prognosis. Without radical treatment, death usually occurs within 2–3 years of diagnosis. Allogeneic stem cell transplantation (allogenic stem cell transplantation) is considered the only potential cure, achieving success in 30–70% of patients.
One of the most formidable complications is disease progression with transformation into leukemia (leukaemia). Leukaemic conversion (leukaemic conversion) can manifest on imaging as lytic bone destruction (e.g., of the iliac crests) and the development of an aggressive extraosseous soft-tissue mass (extraosseous soft-tissue mass).
Additional systemic manifestations include joint syndrome (occurring in 5–20% of patients). Arthropathy most commonly arises due to:
- Haemarthrosis (haemarthrosis).
- Secondary gout (secondary gout).
- Direct infiltration of the synovial membrane by bone marrow elements, leading to polyarthralgia and the development of polyarthritis.
Briefly: answers to topical questions
What conditions must be differentiated from diffuse osteosclerosis in myelofibrosis?
Diffuse osteosclerosis in myelofibrosis must be differentiated from disseminated prostate cancer metastases and Paget's disease.
- Prostate cancer metastases (Prostate) — disseminated osteoblastic lesions can produce confluent sclerosis on radiographs, mimicking the pattern of myelofibrosis.
- Paget's disease — may also be accompanied by confluent sclerosis, but it can be reliably ruled out by the absence of characteristic bone expansion.
What changes in the spleen and liver are detected in myelofibrosis on abdominal CT?
Abdominal CT in primary myelofibrosis reveals marked hepatosplenomegaly caused by the development of extramedullary hematopoiesis.
- Hepatosplenomegaly — is the most frequent manifestation of extramedullary haematopoiesis (extramedullary haematopoiesis).
- Foci of extramedullary hematopoiesis — can be visualized on CT as lobulated, non-calcified soft-tissue masses containing areas of fat density.
What is the cellular and molecular pathogenesis of osteosclerosis development in myelofibrosis?
The pathogenesis of osteosclerosis in myelofibrosis is based on the neoplastic proliferation of bone marrow cells followed by the activation of fibrosis and neo-osteogenesis.
- Cellular proliferation — proliferation occurs predominantly in megakaryocytes and granulocytes.
- Molecular factors — abnormal megakaryocytes and platelets release growth factors.
- Fibrosis — activated fibroblasts cause massive proliferation of reticulin and collagen fibers.
- Bone sclerosis (bone sclerosis) — new trabecular and endosteal bone tissue is formed, causing narrowing of the medullary canal.
The rule of three "S"s for the radiological picture of myelofibrosis: Sclerosis (axial skeleton), Stenosis/narrowing (of the medullary canal), Signal drop (on T1 and T2 MRI).
Class and exam questions
What does bone marrow look like in myelofibrosis on MRI?
Diffuse or heterogeneous decrease in signal intensity (hypointensity) is observed on T1- and T2-weighted images due to the replacement of normal tissue with fibrosis and bone trabeculae.
Why does the medullary canal narrow in myelofibrosis?
Canal narrowing occurs due to the pathological formation of new endosteal and trabecular bone tissue (osteosclerosis).
What joint changes are characteristic of this disease?
Arthropathy is possible (in 5–20% of cases), associated with hemarthrosis, secondary gout, or synovial membrane infiltration by bone marrow cells.
What else to study on this topic
- Pathogenesis of extraosseous soft-tissue mass formation in leukemic transformation
- Mechanisms of secondary gout development in myeloproliferative neoplasms
- Differential diagnosis of the bone scan "superscan" pattern
- Dynamics of bone marrow MRI findings before and after stem cell transplantation
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