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Neuroradiology Case of the Week

Case 225

Uchendu Azodo, MD, Sudhir Kathuria, MD, and P-L Westesson, MD, PhD, DDS

Clinical Presentation: Left-sided tonsillar mass with significant post-biopsy bleeding.

Imaging Findings: Prior CT showed this irregular mass which even causes airway narrowing (Figs. 1& 2). MRs done at the same time show scattered high signal on T2-weighted imaging (Fig. 3); with heterogeneous, predominantly peripheral enhancement on T1-weighted imaging (Figs. 4&5) and central low-signal that signifies necrosis.

Diagnosis: Mixed-cell malignant neoplasm

Discussion: Initial presentation was with a progressively enlarging mass that was very bloody at biopsy.
     While there are benign neoplasms, tendency towards bleeding or hemorrhage is often seen with neovascularity. Even without discrete evidence of invasion, imaging characteristics like this patient’s with heterogeneity, avid enhancement, and necrosis warrant investigation. Barring the benign neoplasms, the differential of malignant lesions includes: mucoepidermoid carcinoma, adenoid cystic carcinoma, squamous cell carcinoma, adenocarcinoma, and acinic cell carcinoma (more common in children). Undifferentiated subtype is even more rare.
     Mixed-cell malignant tumors are behind mucoepidermoid and adenoid cystic carcinomas in terms of prevalence for adult patients. They can also develop from pre-existing benign pleomorphic adenomas, which are actually common benign tumors of the parotid. For this reason, surgical enucleation is usually done, followed by radiation therapy. Recurrence is a well-known risk, and the facial nerve is often injured unavoidably or frankly sacrificed.

References:

1. Neuroradiology Requisites, 2nd Ed., 706-712.
2. E-medicine at http://www.emedicine.com/radio/topic530.htm