Not all myeloid sarcomas have a liquid friend! Myelosarcoma of the sacrum accompanied by severe myelofibrosis

Myeloid sarcoma is a rare disease with poor prognosis. It is characterized by tumor masses composed of myeloblastic cells and usually occurs in association with acute myeloid leukemia. A 71 year old female with past medical history of essential thrombocytosis for 15 years. She was asymptomatic at diagnosis, but began experiencing early satiety 1 year prior and was found to have splenomegaly and was started on hydroxyurea without improvement of her symptoms. This time, she presents to the emergency department with severe painless vaginal bleeding for 2 days. A complete blood count revealed severe thrombocytopenia (14,000/µL). Patient reported she was started on ruxolitinib for four months prior but denied any prior bleeding episodes. CT scan was obtained due to concern for a gynecologic malignancy; which revealed a para-spinous soft tissue mass around L4 level protruding into the psoas muscle. CT-guided biopsy of the sacrum was subsequently performed. Histology reported myeloid myeloperoxidase-positive elements. Immunohistochemical stains showed CD34-positive myeloblasts and CD-117-positive immature myeloid elements accounted for 20% of nucleated elements, compatible with the diagnosis of myeloid sarcoma. Bone marrow biopsy showed extensive fibrosis with no significant hematopoiesis and only 1% of myeloblasts. Bleeding resolved after several platelets transfusions and she was discharged with plans to start chemotherapy as outpatient. Her clinical course was complicated with septic shock during chemotherapy; she expired four months after her initial visit to the ED.