Images below require Macromedia's Flash Player to view

Neuroradiology Case of the Week

Case 79

Ravinder Sidhu MD, Henry Wang MD, PhD, and P-L Westesson MD, PhD, DDS

Clinical Presentation: A 15-year-old male with a history of leukemia and bone marrow transplant presented with aphasia and right-sided weakness.

Radiological Findings:  Non-contrast enhanced head CT showed homogeneously hyperdense lesions in the posterior fossa adjoining the cranial vault. The lesions were seen to extend along the cerebellopontine angle cisterns (Fig. 1A). The stalk of the pituitary gland was also thickened (Fig. 1B). Head CECT revealed mild enhancement of posterior fossa lesions and homogeneous enhancement of the thickened pituitary stalk (Figs. 2A & 2B). Axial T1-weighted MR image showed these lesions to be iso to hypointense as compared to brain parenchyma (Fig. 3A). T2-weighted MR image showed them to be of a hyperintense nature (Fig. 3B). Post-contrast MR images showed mild enhancement of the posterior fossa lesions as well as of thickened pituitary stalk (Figs. 3C & 3D).

Diagnosis: Granulocytic sarcoma (chloroma)

Discussion:  Granulocytic sarcoma is a rare extramedullary collection of granulocytic cells, also known as chloroma. Burns first described this tumor in 1811 [1]. In 1853, King initially called it chloroma, because typical forms have a green color caused by high levels of myeloperoxidase in these premature cells. Granulocytic sarcoma (the preferred term, as not all lesions have the greenish tint) occurs primarily in 3-8% of all patients with acute/chronic myelogenous leukemia, but can also arise in patients with other myeloproliferative disorders, such as myelofibrosis with myeloid metaplasia, hypereosinophilic syndrome, polycythemia vera, and acute lymphoblastic leukemia. It is more frequently seen in the pediatric population without sex predilection. Granulocytic sarcomas may develop during the course of, or as a presenting sign of, myelogenous leukemia. These tumors often occur in multiples and can involve any part of the body [2,3].
     On head CT, granulocytic sarcomas are usually seen as iso to hyperdense extraaxial masses with mild enhancement on contrast administration. On MR imaging, granulocytic sarcomas are typically iso- to slightly hypointense on T1- and isointense on T2-weighted images. They may show uniform enhancement with gadolinium administration. Intracranial granulocytic sarcomas usually occur adjacent to the inner calvarial table and present as extraaxial masses [4,5].
     It is believed that intracranial granulocytic sarcomas develop by migration of leukemic cells from the bone marrow via haversian canals, periosteum, and the dura to infiltrate the brain, where the pial-glial barrier has been disrupted. Thus, granulocytic sarcomas may simulate meningiomas or may present as cerebellopontine-angle masses such as acoustic neuromas. A high level of suspicion is necessary, because early, and accurate diagnosis is important for a favorable prognosis [6].

References:

1. Burns A. Observations of Surgical Anatomy: Head and Neck. Edinburgh: Thomas Royce and Company; 1811: 364-366.
2. Guermazi A, Feger C, Rousselot P et al. Granulocytic sarcoma (chloroma): Imaging findings in adults and children. AJR Am J of Roentgenol. 2002; 178:319-325.
3. Cho JS, Kim EE, Ro JH, Pinkel DP, Goepfert H. Mandibular chloroma demonstrated by magnetic resonance imaging. Head Neck.1990; 12: 507-511.
4. Pui MH, Fletcher BD, Langston JW. Granulocytic sarcoma in childhood leukemia: imaging features. Radiology.1994; 190:698-702.
5. Lee B, Faterrpekar GM, Kim W, Som PM. Granulocytic sarcoma of the temporal bone. AJNR Am J Neuroradiol. 2002; 23:1497-1499.
6. Nikolic B, Feigenbaum F, Abbara S, Martuza RL, Schellinger D. CT changes of an intracranial granulocytic sarcoma on short-term follow-up. AJR Am J Roentgenol. 2003; 180:78-80.