Myeloid Sarcoma of the Orbit Preceding Acute Myeloid Leukaemia: A Diagnostic Challenge

Objective- Myeloid sarcoma is a rare form of acute myeloid leukaemia characterized by extramedullary proliferation of myeloid blasts which can occur as an isolated lesion in any organ. Even rarer it may occur in the orbit as the initial presentation without a leukaemic phase and diagnosis may be challenging when it is not suspected. Methods- We report a case of orbital myeloid sarcoma as the initial presentation of acute myeloid leukaemia in an adult who was misdiagnosed and treated as a case of a pseudotumour with resultant significant disease progression and worsening of the clinical condition. There was a lag of four months from the onset of eye mass to the development of acute myeloid leukaemia. Result- Due to patients worsening condition and tumour progression, a repeat biopsy for a second histology opinion at a different facility, immunophenotyping and immunohistochemistry were employed to arrive at the correct diagnosis. Following chemotherapy, the orbital mass reduced markedly and clinical condition improved. The patient was indigent and could not sustain further funding of his treatment because he had already spent much on for management of complications he developed before a definitive diagnosis could be made. Conclusion- Myeloid sarcoma can present as an orbital mass without a leukemic disease. Therefore a high index of suspicion, meticulous examination of biopsy, immunohistochemistry and collaboration between oncologists and ophthalmologists, are required to arrive at an early accurate diagnosis.