Images below require Macromedia's Flash Player to view

Neuroradiology Case of the Week

Case 301

Scott Rudzinski, Ben Wandtke, MD, and P-L Westesson, MD, PhD, DDS

Clinical Presentation: A 69-year-old male presents with new onset of right-sided ptosis.

Imaging Findings: The right lacrimal gland is markedly enlarged, homogeneous in signal on all sequences, and demonstrates moderate enhancement. Diffusion weighted imaging shows high signal consistent with restricted diffusion indicating a high cellular density typical of lymphoma.

Diagnosis: Lacrimal gland lymphoma

Discussion: Lymphoid masses constitute 10-15% of orbital masses. When malignancy is considered, lymphoma is the dominant tumor, occurring in up to 55% of cases. Orbital involvement is present in 1-5% of patients with systemic lymphoma. Lymphoproliferative lesions can arise in the orbit itself, or when extraconal, are referred to as orbital adnexal lesions. The vast majority of orbital adnexal lesions involve the lacrimal gland and lacrimal fossa. These lesions can be very difficult to differentiate both radiologically and pathologically.
     The lacrimal gland is located in the superior lateral aspect of the orbit, within the lacrimal fossa adjacent to the superior and lateral rectus muscles. It consists of the anterior palpebral and deeper orbital lobes which are demarcated by the lateral horn aponeurosis of the levator palpebrea superioris. Whereas most other lacrimal tumors develop in the deeper orbital lobe, lacrimal lymphomas involve the entire lacrimal gland diffusely.
     Approximately half of lacrimal gland lesions are tumors of epithelial origin, of which half are pleomorphic ademonas and half are carcinomas. The other half of lacrimal gland lesions are lymphoproliferative in nature. Lymphomatous lesions of the lacrimal gland include a broad spectrum of disease entities ranging from benign dacryoadenitis to malignant lymphoma. Other lacrimal gland lesions include dermoid cysts and intrinsic epithelial cysts arising from the lacrimal duct. Pseudotumors, which are nonspecific inflammatory mass lesions of the orbital tissue, may also occur in the lacrimal region. Primary lacrimal gland lymphomas are typically B-cell tumors, a high proportion of which have mucosa-associated lymphoid tissue (MALT) characteristics.
     MR is the modality of choice for evaluating location and extent of disease. On MR imaging lacrimal lymphoma is homogenous and mildly hyperintense to extraocular muscles on T1 and T2WI, although the cellular nature of lymphoid infiltrate causes lower T2 signal intensity that many other malignancies. CT of lacrimal lymphoma characteristically shows a well-circumscribed lesion of greater than brain density, molding to adjacent tissues with moderate enhancement. Calcification is rare. Aggressive histology is associated with bone destruction, while molding is more characteristic of indolent histology. Lymphoma is typically homogeneous, while hyperplasia is often heterogeneous. However, neither MR or CT can reliably distinguish between hyperplasia and lymphoma. Histopathology is necessary for diagnosis in all cases.
     Following the diagnosis of lymphoma, appropriate follow up studies are necessary for staging. One study found that PET upstaged 71% of patents with systemic lymphoproliferative involvement, having a higher sensitivity than CT in detecting distant disease. The same study showed that gallium scanning provides no additional information to CT and does not influence patient treatment.
     Prognosis is determinant on the stage of lymphoma, with good prognosis for low stage lesions and very good prognosis of MALT lesions following radiotherapy. Long term prognosis for systemic disease is poor.

References:

1. Akansel G, Hendrix L, Erickson BA, Demirci A, Papke A, Arslan A, Ciftci E. MRI patterns in orbital malignant lymphoma and atypical lymphocytic infiltrates. Eur J Radiol. 2005 Feb;53(2):175-81. [Medline]
2. Balchunas WR, Quencer RM, Byrne SF. Lacrimal gland and fossa masses: evaluation by computed tomography and A-mode echography. Radiology. 1983 Dec;149(3):751-8. [Medline]
3. Farmer JP, Lamba M, Lamba WR, Jordan DR, Gilberg S, Sengar DP, Bence-Bruckler I, Burns BF. Lymphoproliferative lesions of the lacrimal gland: clinicopathological, immunohistochemical and molecular genetic analysis. Can J Ophthalmol. 2005 Apr;40(2):151-60. [Medline]
4. Sullivan TJ, Valenzuela AA. Imaging features of ocular adnexal lymphoproliferative disease. Eye. 2006 Oct;20(10):1189-95. [Medline]
5. Valenzuela AA, Allen C, Grimes D, Wong D, Sullivan TJ. Positron emission tomography in the detection and staging of ocular adnexal lymphoproliferative disease. Ophthalmology. 2006 Dec;113(12):2331-7. [Medline]
6. Jung WS, Ahn KJ, Park MR, Kim JY, Choi JJ, Kim BS, Hahn ST. The radiological spectrum of orbital pathologies that involve the lacrimal gland and the lacrimal fossa. Korean J Radiol. 2007 Jul-Aug;8(4):336-42. [Medline]