Diagnostic Dilemma: Severe Sepsis Causing Inflammation Mimicking Secondary Myeloid Sarcoma in Newly Diagnosed Acute Myeloid Leukemia
Authors: Horne Caroline G , Singh Jai 
Published: December 2024

A 57-year-old female with presented to the hospital for a one-week history of fevers, fatigue, and generalized weakness after a recent admission for sepsis secondary to pneumonia. On arrival, she was febrile to 102.5F, tachypneic, tachycardic, and normotensive with exam notable for bibasilar crackles and lethargy. Chest x-ray revealed vascular congestion and small bilateral pleural effusions with adjacent atelectasis. Her labs showed hyponatremia, hyperglycemia, and normocytic anemia without elevated lactic acid nor leukocytosis. She was admitted and started on broad spectrum antibiotics for presumed pulmonary infection; however, the next day her labs revealed 10% blasts and pancytopenia. A peripheral blood smear demonstrated myeloblasts concerning for acute myeloid leukemia, with confirmation via bone marrow biopsy and peripheral flow cytometry. Further testing included negative BCR/ABL1 PCR, negative AML FISH, and increase in peripheral blasts (up to 53% on CBC).

She completed induction chemotherapy with a 7-day continuous infusion of Cytarabine (100 mg/m2) with Daunorubicin (60 mg/m2) on days 1-3 (“7+3 Therapy”) in hopes for disease control. Her hospital course was complicated by intubation for acute hypoxic respiratory failure, hemodialysis for acute renal failure, ongoing fevers, atrial fibrillation with rapid ventricular rates, hypotension requiring vasopressor support, progressive pancytopenia requiring blood product transfusions, and stress cardiomyopathy (ejection fraction 40%). Fortunately, she gradually began to improve; however, there was then an incidental finding of possible calcific density near the left ventricle on follow up CT scan, that was also noted on serial echocardiogram (2.5 cm x 1.5 cm). Further evaluation with cardiac MRI showed improved ejection fraction (67%) and a focal mass in the distal interventricular septum notable for its fixed intramural/anterior ventricular position concerning for an infiltrative, metastatic leukemic focus. Cardio-oncology was consulted for concern of myeloid sarcoma who recommended PET/CT scan revealing a partially calcified lesion (1.9 cm x 2.7 cm) along the cardiac interventricular septum (max SUV 5.4) along with other small metabolically active soft tissue lesions along muscular regions.

There was concern for infiltrative metastatic disease given unique MRI features of low T1 value with diffuse gadolinium uptake, hypermetabolism on PET/CT (max SUV 5.4), and the thought that the calcified/hyperintense CT characteristics were representative of densely packed cells. It was agreed that she would require biopsy for further evaluation of this cardiac lesion prior to undergoing stem cell transplant. The patient underwent image-guided biopsy of extra-cardiac muscular regions with interventional radiology; however, pathology was non-diagnostic. Subsequent endomyocardial biopsy was also negative for malignancy; however, it was felt this did not completely exclude the possibility of myeloid sarcoma, so stem cell transplant was deferred pending further evaluation. Repeat cardiac MRI about 4 weeks later revealed persistence of previously seen cardiac mass with stable characteristics.

The patient later underwent surgical cardiac biopsy with cardiothoracic surgery since repeat endomyocardial biopsy was felt to be low yield given that myeloid sarcomas are often deeply infiltrative. Frozen sections of this specimen revealed calcium, fibrosis, and lymphocytes, but no evidence of malignancy and her final pathology without evidence of malignancy; instead, showing focal and dystrophic calcifications, fibrosis, perivascular inflammation, and hemosiderin-laden macrophages. The multidisciplinary team cleared the patient to undergo stem cell transplant for AML after confirming the calcific, metabolically active cardiac mass was not a secondary myeloid sarcoma or metastases. It was felt that this cardiac mass was a very rare event that was most likely triggered by the patient's severe sepsis and acute renal injury requiring hemodialysis at the time of her AML diagnosis which resulted in local tissue damage and calcium deposits in the interventricular septum. The high degree of inflammation during this time was felt to explain why it appeared metabolically active on PET and enhanced on MRI. This case highlights a rare, but important consideration in severely ill patients with acute myeloid leukemia.