Pleomorphic adenoma and dentigerous cyst
Enlarging right parotid gland with known background of pleiomorphic adenoma of the left parotid
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The is a 24 mm x 21 mm x 38 mm multilobulated, well circumscribed mass lesion within the left parotid tail, demonstrating heterogeneous signal and contrast enhancement. The medial margin of the lesion contacts the left mandibular angle, however, there is no extent into the deep lobe of parotid demonstrated. There is no abnormal mandibular marrow signal and no abnormal perineural enhancement involving the left facial or V3 nerves.
The contralateral parotid gland appears unremarkable. Prominent cervical chain and submandibular lymph nodes demonstrated bilaterally, likely inflammatory.
There is an encapsulated cystic lesion associated with an unerupted right maxillary tooth with T1 high signal content that demonstrates restricted diffusion - likely representing a inspissated dentigerous cysts.
No regions of high-grade cervical canal stenosis. No abnormal cervical marrow infiltration.
The imaging morphology of the well-defined parotid lesion is in keeping with a pleomorphic adenoma involving the left parotid tail without involvement of the deep lobe of parotid.
The right parotid gland appears normal.
An inspissated, likely dentigerous cyst is noted in the right maxillary sinus associated with an unerrupted tooth.
Left parotid tissue: An irregular piece of parotid gland, 35g, 60mm inferior to superior, 40mm medial to lateral, 50mm anterior to deep. Sectioning reveals a well circumscribed, solid white mass 40x25x25mm. The mass abuts both medial and lateral margins and is well clear of all other margins.
The sections of the parotid gland show a variably encapsulated tumour with a biphasic composition. There are hypercellular chondromyxoid areas populated by spindle cells and more cellular areas with epithelioid cells forming trabecular cysts and tubules. There is no evidence of malignant change. The lesion appears to be completely excised with all margins clear of tumour.
Left parotid tissue: Pleomorphic adenoma; all margins clear of tumour.
Key learning points:
1. Small pleomorphic adenomas are usually homogenous in signal.
2. Dentigerous cysts can be located within the maxillary sinus.