Olgu Arşivi

59 year old woman was diagnosed with right sided Bell’s palsy in March. The facial paralysis didn´t improve and a small mass could be palpated in the right parotid gland. CT was requested at the end of April, the exam was originally interpreted as normal. As the facial paralysis didn´t improve during the summer the CT was re-interpreted and MRI performed in August.  

Differential diagnoses:

- Benign mixed tumor, aka pleomorphic adenoma

-Carcinoma ex pleomorphic adenoma with perineural spread

-Whartin tumor

-Salivary gland malignancy with perineural spread

- Non Hodgkin lymphoma with perineural spread


Cranial nerves involved:

- Facial nerve and maxillary nerve

- Facial nerve and mandibular nerve

- Facial nerve and ophthalmic nerve

- Facial nerve and glossopharyngeal nerve


Diagnosis

- Salivary gland malignancy

- (Adenoid cystic cancer according to pathology)

- Perineural spread along facial and mandibular nerves

- Lymph node metastasi


Imaging findings 

- contrast enhancing mass in the right parotid gland (thick arrow a,e,f)

- growing along the facial (thin arrow, a,e,f)

- and mandibular nerves (zigzag arrow b,c,d)

- foramen ovale is widened and the tumor extends intracranially up to the cavernous sinus (zigzag arrow b,c,d)

- the mass has low signal on T2 low ADC value (star on g).

- metastatic lymph node (medium arrow, h) 


Benign mixed tumor, aka pleomorphic adenoma

- Benign tumor arising from distal portions of parotid ductal system

- Manifests as painless cheek mass

- Patients are usually older than 40 years

- T2 signal can be very high, higher than CSF, ADC values are high

- Signal in bigger tumors can be heterogenous due to necrosis, hemorrhage and calcification

- Dynamic contrast MRI shows quick uptake then plateau 


Carcinoma ex pleomorphic adenoma

- Rapid enlargement of longstanding parotid mass

- Facial nerve weakness and pain

- Early tumor: indistinguishable from benign mixed tumor

- Late tumor: aggressive, infiltrating parotid mass

- T2 signal is higher than other tumors


Whartin tumor

- Painless mass in the parotid tail (angle of the mandible)

- 90% of the patients with this tumor is smoker

- 20% of cases can be multiple masses

- Sharply marginated, heterogenic mass

- Lesion is most conspicuous on STIR sequence

- ADC value is similar to cancer

- Takes up FDG


Salivary gland malignancy with perineural spread

- (mucoepidermoid cancer or adenoid cystic carcinoma)

-  Malignant tumors arising from the parotid ducts

- Manifests as palpable, hard, painful parotid mass

- Often combined with cranial nerve symptoms (ex. facial nerve palsy)

- T2 signal is lower than benign tumor´s

- Always look after perineural tumor growth


Non-Hodgkin lymphoma with perineural spread

- Slowly enlarging parotid mass with our without nodes on the neck

- Patient may have systemic “B” symptoms

- Different imaging features for nodal and primary parenchymal lymphoma

- Intermediate or low T2 signal, low ADC value

- FDG avid (MALT lymphoma is not so FDG avid)


Connections between trigeminal and facial nerves

- Parotid gland: auriculotemporal nerve (V/3) & facial nerve

- High masticator space: lingual nerve (V/3) & chorda tympani

- Otic ganglion under skull base: V/3 & lesser petrosal nerve

- Pterygopalatine fossa: two pterygopalatine nerves from V/2 & Vidian nerve (n petrosus maior)

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