Background
Extramedullary haematopoiesis (EMH) pertains to the creation of non-cancerous blood cell lineages outside the bone marrow. It is frequently an unexpected discovery during imaging of patients with haematologic conditions. The manifestation of EMH in the form of a mass (referred to as tumefactive EMH) has posed a challenge in radiology, given its resemblance to tumours. The radiological appearance varies depending on the lesion’s age and the level of hematopoietic activity. More mature lesions exhibit deposits of hemosiderin and fat, while newer lesions can closely resemble tumours [1].
Clinical Perspective
EMH usually involves the liver, spleen, and lymph nodes. It can also be found at paravertebral, intrathoracic, or pelvic locations. Intracranial EH is a rare entity and often asymptomatic but can sometimes lead to symptomatic tumour-like masses. It can present with hepatosplenomegaly, lymphadenopathy, and multiple lobulated paraspinal posterior mediastinal mass. CNS involvement is rare but not uncommon [2,3].
Imaging Perspective
Imaging of CNS manifestations of EMH include Smooth multifocal/solitary homogenous juxta dural, juxtaspinal masses with varying appearance based on activity/age of the lesion. Presence of macroscopic fat is also suggestive of EMH. Homogeneous enhancement is seen in postcontrast images, burnt-out lesions show minimal enhancement. CT, MRI and Tc-99m sulfur colloid can be helpful for diagnosis. Final diagnosis can be made by histopathological examination [4].
Outcome
Treatment options include treatment of primary underlying pathology. Low-dose radiotherapy can be used as hematopoietic tissues are sensitive to radiation. Surgical resection can be treatment option in lesions with compressive myelopathy, and large CNS lesions [5]. The behavioural, urinary and motor symptoms of the patient improved after surgery.
Take Home Message / Teaching Points
Extramedullary haematopoiesis (EMH) is the development of blood cell lineages outside the bone marrow, often associated with haematological disorders. In rare cases, EMH can manifest as intracranial lesions, presenting diagnostic challenges due to their resemblance to tumours. We present a case of a 61-year-old patient with a history of chronic hepatitis B infection, who exhibited neurological symptoms including transient weakness, urinary incontinence, and behavioural changes. Imaging revealed a solitary dural-based mass along the falx cerebri with associated superficial siderosis. The lesion demonstrated T1 isointenseT2/FLAIR iso to hypointense signal, and a hemosiderin rim, along with surrounding vasogenic oedema. Further imaging depicted areas of blooming within the mass and adjacent structures. The patient underwent surgical excision, and histopathology confirmed the presence of immature bone marrow elements, resulting in a diagnosis of intracranial EMH. Siderosis can be explained by the presence of active haematopoiesis leading to iron products This case highlights the importance of considering EMH as a differential diagnosis for intracranial lesions in individuals with underlying haematological disorders. Understanding the varied radiological appearances of EMH aids in accurate diagnosis, mitigating unnecessary investigations and treatment expenses. This report underscores the significance of interdisciplinary collaboration in managing such cases and sheds light on the uncommon manifestation of EMH in the central nervous system.
