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Neuroradiology Case of the Week

Case 96

Andrea Zynda-Weiss MD and PL Westesson, MD, PhD, DDS

Clinical Presentation: Patient is a 35-year-old male with a six month history of painless “ridge” over his right eye. On the day of admission, patient felt a “pop” over his right eye while blowing his nose. He developed pain and presented to the Emergency Department. Physical exam revealed mild proptosis and decreased lateral gaze on the right. There was swelling over the right orbit but no erythema. CT was performed.

Radiological Findings: CT demonstrates an expansile lytic lesion centered in the zygomatic-sphenoid suture. There is an extraconal soft tissue component exerting mass effect on the lateral rectus muscle and causing proptosis. There is extension to the temporalis muscle.
     MRI demonstrated a destructive mass with enhancement and central necrosis involving the lateral wall of the right orbit and sphenoid wing. The soft tissue component extends along the inner surface of the frontal bone and middle cranial fossa, displacing the frontal and temporal lobes. The mass also involves the infratemporal fossa and temporalis muscle.
     CT of the abdomen and pelvis was done to look for additional lesions. Lytic lesions were seen in the sacrum and left iliac wing. No adenopathy was identified.
     Biopsy was performed of the orbital and sacral lesions.

Diagnosis: Lymphoblastic lymphoma/leukemia, B-cell origin

Clinical Discussion:  Extra-nodal presentation of lymphoma is common and lymphoid tumors account for 10-15% of orbital masses [1]. True lymphoid tissue is found in the subconjunctival and lacrimal glands, where most of the lymphoreticular disorders involving the orbit develop [1]. Orbital lymphomas tend to form soft tissue masses surrounding the orbital structures without causing bony erosion. However, aggressive malignant lymphomas can destroy the bone [2]. Leukemia directly infiltrates the orbital bone or soft tissues [1]. In patients with acute myelogenous leukemia (AML), tumor infiltration can form a granulocytic sarcoma, which is also known as a chloroma because of its green hue on gross examination [1,3]. This may be the first manifestation of AML. A chloroma typically involves the subperiosteal space of the lateral wall of the orbit with extension to the temporal fossa [1].
     The differential diagnosis of extra-conal orbital lesions involving the bone includes lymphoma/leukemia, metastasis, multiple myeloma, fibrous histiocytoma , ossifying fibroma, subperiosteal abscess, subperiosteal hematoma, meningioma of the sphenoid wing, osteomyelitis, Paget’s disease and fibrous dysplasia [1,4,5]. Fibrous dysplasia causes general expansion of the sphenoid or frontal bones with no definable soft tissue mass (6). Ossifying fibromas are dense on CT [6]. In an adult, the most common tumors to metastasize to bone are breast, lung, prostate, melanoma, gastrointestinal and kidney (6). Fibrous histiocytoma is the most common orbital tumor in adults [6].
     In a child the differential diagnosis also includes Ewing’s sarcoma, aneurysmal bone cyst, and eosinophilic granuloma/histiocytosis X [2].
      In a similar case, an 85-year-old man had a head CT for mental status changes after a fall. An expansile, lytic lesion was found in the right greater wing of the sphenoid.
     Further investigation revealed a history of metastatic prostate cancer with a known metastasis to the sphenoid bone.

References:

1. Som PM, Hugh D, ed. Head and Neck Imaging, 4th ed. Mosby, St Louis, 2002.
2. Looi ALG, Choo CT et al. An Unusual Orbital Bone Lesion. Singapore Med J. 2001 Vol 42(1): 038-040.
3. Stockl FA, et al. Orbital Granulocytic Sarcoma. Br J Ophthalmol. 1997; 81:1084-1088.
4. Harnsberger HR. Handbook of Head and Neck Imaging, 2nd ed. Mosby, St. Louis, 1995. pp 334-36.
5. Dahnert W. Radiology Review Manual, 4th ed. Lippincott Williams and Wilkins, Philadelphia 2000.
6. Darsaut TE, et al. An Introductory Overview of Orbital Tumors. Neurosurg Focus. 10 (5), 2001.