Clinical History
A 26 year old woman with a myeloid blast crisis of CML, presented with a progressive history of pain and swelling of the left shoulder.
Imaging Findings
The patient was diagnosed with CML in Chechnya in 1995. She was treated with Hydroxyurea, splenic irradiation and Anthracycline. She moved to the UK in 2000 with a documented myeloid blast crisis and was commenced on Mitozantrone therapy and planned for a bone marrow stem cell transplant. In November 2001 she presented with a progressive history of left shoulder pain and swelling. Plain film radiography demonstrated an aggressive lytic lesion with cortical destruction, involving the glenoid cup and coracoid process, with an overlying soft tissue mass surrounding the left scapula. An isotope bone scan, MRI and a CT guided biopsy were performed.
Discussion
In the clinical context of leukaemia, the differential diagnosis included haematoma, localised infection and secondary tumours. Histological examination revealed a granulocytic sarcoma (also known as 'Chloroma').
Granulocytic sarcoma is an extramedullary solid tumour of granulocytic precursor cells at various stages of differentiation. It is usually found in association with acute myelogenous leukaemia (AML), most commonly during the progression of the disease (it occurs in 2.5-8% of people with AML). However, it may also precede haematological findings by months or years, or be the primary presentation of AML. In patients with AML it is twice more common in children than adults. It is also seen in association with CML and myeloproliferative disorders where it often heralds the onset of a blast crisis sometimes before clinical or haematological signs.
Granulocytic sarcoma can occur at almost any site and are often multifocal with a high recurrence rate (23%) occurring at different stages of the disease and at different sites.
CT of granulocytic sarcoma often shows a homogenous soft tissue mass usually isodense to muscle. If involving bone, lytic destruction can be seen. On MRI it is characteristically isointense to muscle on T1- and mildly hyperintense to muscle on T2- weighted sequences. Within the brain, granulocytic sarcomas are often extra-axial masses, hyperdense on unenhanced CT, and isointense to grey matter on T1- and T2- weighted MR images. Following injection of contrast media in both CT and MRI, lesions usually enhance homogenously, however occasionally there can be rim enhancement, which therefore may mimic an abscess.
The use of special immuno-histochemical stains is required to assist in making the diagnosis. Imaging alone is generally insufficient to make a diagnosis, but granulocytic sarcoma should be strongly considered if a patient with a myelogenous leukaemia presents with a soft tissue mass. It is important to make a prompt diagnosis of granulocytic sarcoma, not only as it may herald the onset of an acute systemic leukaemia, but also to instigate early treatment as they are very sensitive to focal irradiation.
Differential Diagnosis List