Granulocytic sarcoma

A granulocytic sarcoma (also called myeloid sarcoma and chloroma) is a rare neoplasm comprised of myeloid precursor cells. 

It can occur in association with 

• acute myeloid leukaemia (AML)
• chronic myeloid leukaemia (CML)
• othermyeloproliferative disorders such as 
  • myelofibrosis with myeloid metaplasia
  • hypereosinophilic syndrome or 
  • polycythemia vera

Epidemiology

It is typically seen is in children with ~ 60% occurring in individuals less than 15 years of age. There is no recognised gender predilection.

Granulocytic sarcoma may develop during the course of a hematologic disorder; it only precedes the disorder in 35 % of cases.

Pathology

Granulocytic sarcoma lesions are composed of immature myeloid elements and therefore represents focal accumulation of leukaemic cells.  In contrast to its associated entities, the lesion(s) take the form of a solid soft tissue mass(es). 

Location

Being extramedullary is a key feature

Almost any tissue can be affected, with skin and bone being the commonest. They have been reported in the skull, face, orbit and paranasal sinuses. Lesions have been reported in the tonsils, oral and nasal cavities and within the lacrimal, thyroid and salivary glands. The central nervous system can also be affected. 

Radiographic features

Exact imaging features will depend on the location and involved organ.

Refer to 

• CNS manifestations of granulocytic sarcoma
• spinal manifestations of granulocytic sarcoma - see article : spinal leukaemia
• head and neck manifestations of granulocytic sarcoma
• skeletal manifestations of granulocytic sarcoma
• abdomimal manifestations of granulocytic sarcoma
• thoracic manifestation of granulocytic sarcoma

Etymology

• first described by A Burns in 1811 ³
• termed "chloroma" in 1853 byKing due to typical forms havea green color from high levels of myeloperoxidase inimmature cells.
• renamed as granulocytic sarcoma in1966 by Rappaport due later findings that not all of the cells are green