BACKGROUND Granulocytic sarcoma, or 'chloroma,' due to extramedullary acute myeloid leukemia (AML) or due to acute myelomonocytic leukemia (AML M5), is rare and is associated with a poor prognosis. This report is of a case of granulocytic sarcoma of the gallbladder and describes the approach to diagnosis and treatment.

CASE REPORT A 74-year-old Hispanic woman from Ecuador presented to the emergency department with a five-day history of fever, jaundice, and right upper quadrant abdominal pain. The right upper quadrant ultrasound showed a thickened gallbladder wall with cholelithiasis, a positive sonographic Murphy sign, and marked dilatation of the common bile duct, which was up to 17 mm in diameter. Endoscopic retrograde cholangiopancreatography (ERCP) showed purulence and a stone in the common bile duct, which was removed. She underwent laparoscopic cholecystectomy which identified gangrenous cholecystitis. Despite cholecystectomy and treatment with broad-spectrum antibiotics, she remained febrile with a leukocytosis of up to 80,000 cells/microL. Histopathology of the gallbladder showed infiltrating myeloblasts within the mucosa, submucosa, and muscularis consistent with a granulocytic sarcoma associated with gangrenous cholecystitis due to cholelithiasis. Immunohistochemistry, using a panel of antibodies to CD33, CD68, HLA-DR, and lysozyme, supported the diagnosis of granulocytic sarcoma or extramedullary acute myelomonocytic leukemia (AML M5).

CONCLUSIONS A rare case of an extramedullary hematologic malignancy, granulocytic sarcoma of the gallbladder is presented, which highlights the importance of timely diagnosis and treatment, due to the high mortality rate associated with granulocytic sarcoma, or extramedullary AML.