Case of the Week

Background:

• Carcinoma ex pleomorphic adenoma (CXPA) is a relatively rare tumor, with a prevalence rate of 5.6 cases per 100,000 neoplasms.¹ It is the third most frequent epithelial lacrimal gland tumor.² Most of these tumors arise from pre-existing pleomorphic adenomas and most commonly from the parotid gland, though lacrimal gland involvement has been described.²

Clinical Presentation:

• Proptosis is the most common presenting symptom. The tumor can also involve the nasolacrimal duct, resulting in recurrent dacryocystitis and chronic epiphora. Involvement of the muscles may restrict eye movement, and neural involvement can cause visual/hearing difficulties.²

Key Diagnostic Features:

• MR imaging findings are not specific due to the presence of multiple different tissue types. Characteristically, CXPA will show diffusion restriction due to hypercellularity, along with hemorrhage, necrosis, irregular margins, and infiltration into surrounding tissues including perineural tumor invasion.³ CT is useful to assess for the presence of bony involvement, which is the best indicator of malignant nature.⁴

Differential Diagnoses:

• Pleomorphic adenoma (benign): well-circumscribed mass, smooth bony scalloping, moderate enhancement on CT with contrast, low/intermediate signal on T1 MRI, intermediate signal on T2 MRI
• Adenoid cystic carcinoma/mucoepidermoid carcinoma (malignant): well-defined and homogeneous mass, associated bone destruction, diffuse enhancement on CT with contrast, hypointense on T1, intermediate/high signal on T2
• Sarcoidosis: typically bilateral, lacrimal gland enlargement, hyperenhancement on CT with contrast, hypo-/isointense on T1, heterogeneously hyperintense on T2
• Inflammatory dacryoadenitis: may be unilateral or bilateral, no bone involvement, variable contrast enhancement hypo-/isointense on T1 and T2

Treatment:

• This is primarily surgical, ranging from local resection to complete removal of the eye. Bone removal may also be necessary if tumor infiltration is present. Adjuvant therapy may also be needed depending on tumor grade and invasion.^{1– 3}