Myeloproliferative neoplasms

Extramedullary haematopoiesis and myelofibrosis

Myeloproliferative neoplasms traditionally include primary myelofibrosis (primary myelofibrosis, PMF) and polycythaemia vera (polycythaemia vera).

The primary clinical manifestation in adult patients is splenomegaly and the development of foci of extramedullary haematopoiesis (EMH, extramedullary haematopoiesis). Primary myelofibrosis is the most frequent cause of EMH.

Typical manifestations of extramedullary haematopoiesis include:

• Hepatosplenomegaly (most frequent).
• Development of bilateral paraspinal (paravertebral) masses in the thoracic cavity.
• Marked thickening of the rib structures.
• Appearance of presacral soft-tissue masses.

It is important to remember that myeloproliferative processes have a high potential for transformation into leukaemia (leukaemia).

Imaging features of myelofibrosis and EMH

Diagnosis of these conditions is based on the combined use of various imaging modalities:

• Radiography: the classic sign is bone marrow sclerosis.
• Computed tomography (CT): foci of EMH (e.g., in the presacral region) appear as lobulated, non-calcified soft-tissue masses that may contain areas of fat density.
• Magnetic resonance imaging (MRI): bone marrow hyperplasia or fibrosis manifests as a diffuse or heterogeneous decrease in signal intensity on T1-weighted images (T1WI). The EMH masses themselves demonstrate a heterogeneous signal on both T1- and T2WI.

MRI is actively used to assess process activity: the presence of fat signal within a mass indicates its inactivity. Conversely, marked contrast enhancement (enhancement) confirms the active stage of the process.

Leukaemias: clinical presentation in children and adults

Leukaemias account for about 30% of all childhood malignancies. The vast majority are acute forms originating from immature leukocyte pools.

1. Acute lymphoblastic leukaemia (ALL, ALL): predominates in children (75% of cases), with a peak manifestation at 2–3 years of age.
2. Acute myeloid leukaemia (AML, AML): accounts for 20% of pediatric leukaemias, more commonly detected in the first 2 years of life.
3. Other types: account for the remaining 5%.

The disease in children often has an insidious (insidious) course. Clinically, it presents with non-specific malaise, anorexia, fever, petechiae, and weight loss. Bone pain at onset is documented in more than 33% of children, which is 5 times more frequent compared to adults. Pathological fractures are also quite typical.

Adults are predominantly affected by chronic leukaemias originating from mature cell lines. Chronic lymphocytic leukaemia (CLL, CLL) and AML (incidence 3–4%) are diagnosed most frequently. In CLL, typical for elderly individuals, the spleen and lymph nodes enlarge, while bone involvement is rare (usually considered a terminal state). Overall, in adults, bone lesions are localized in areas retaining residual red bone marrow: the axial skeleton, and the proximal humeri and femora.

Radiographic signs of leukaemias

Skeletal changes in acute childhood leukaemia are detected on radiographs in approximately 40% of patients at initial presentation. Throughout the course of the disease, this figure rises to 75%.

The frequency of radiographic phenomena at initial examination is distributed as follows:

• Osteolysis (osteolysis) — 13.1%
• Metaphyseal bands (metaphyseal bands) — 9.8%
• Osteopenia (osteopenia) — 9%
• Osteosclerosis (osteosclerosis) — 7.4%
• Permeative bone destruction (permeative bone destruction) — 5.7%
• Pathological fractures — 5.7%
• Periosteal reaction (periosteal reaction) — 4.1%
• Mixed lytic and sclerotic lesions — 2.5%

Specific bone changes

In the imaging diagnosis of leukaemias, two specific signs deserve special attention:

Diffuse osteopenia is recorded in 16–41% of cases. It may result from diffuse tumor infiltration of the bone marrow or have a purely metabolic etiology. Chemotherapy and prolonged corticosteroid therapy also contribute. Against the background of marked spinal osteopenia, compression fractures develop, up to the formation of vertebra plana (vertebra plana).

Metaphyseal lucent bands (metaphyseal lucent bands) are bands ranging from 2 to 15 mm in width. Initially, they appear in the distal femur, proximal tibia, and distal radius. As the process progresses, other metaphyses and vertebral bodies become involved. In differential diagnosis, it should be considered that similar bands may occur in infants with generalized infection. However, the detection of such zones in a child older than 2 years makes the diagnosis of leukaemia most likely.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• {'title': 'Mechanisms of blast crisis in chronic leukemias'}
• {'title': 'Pathophysiology of vertebra plana formation in compression fractures'}
• {'title': 'Features of axial skeleton involvement in patients with CLL'}
• {'title': 'Differential diagnosis of permeative bone destruction'}

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