ACC most commonly arises in the salivary glands including the parotid, submandibular, lacrimal and minor salivary glands. It has also been found in prostate, breast, bronchial mucosa, facial sinuses, intestinal and genital tracts and skin.1–4
It has three growth patterns: cribriform, tubular and solid. Predominant solid tumours are associated with the highest metastases and perineural spread.1
ACC is a malignant tumour involving the exocrine glands.
It has a slow growth rate, with frequent perineural and metastatic spread. ACC perineural tumour spread from branches of the trigeminal nerve to invade the cavernous sinus is commonly reported.2 5–7
ACC often has non-specific initial symptoms including non-specific facial pain and non-specific headache. Perineural spread along the trigeminal nerve may be misdiagnosed as trigeminal neuralgia.2
Presentation of a partial cavernous sinus syndrome or an orbital apex syndrome is common.2 8
Later symptoms include diplopia, epistaxis, sinusitis, Bell's palsy, lacrimal gland swelling and proptosis.1 2 9
. Presentation with Horner's syndrome is uncommon.1
An Adie tonic pupil followed by an orbital apex syndrome has been reported.1 2 10 11
The time between the onset of symptoms and diagnosis ranges from 6 months to 6 years.2 8
Radical surgical resection followed by radiotherapy is considered the best treatment for ACC, but surgical margins often involve critical structures due to perineural tumour spread.2
Therefore, incomplete resection is common with local recurrence within 3 years of the initial treatment.2
In patients with complete resection of the tumour, the presence of distant metastases is present in 39% of cases.2
ACC is radiosensitive so tumour size and symptoms can be reduced, but it is not radiocurable as 93% of patients have recurrence within 5 years of radiotherapy.2
As in our case, ACC may mimic schwannoma or meningioma, MRIs were misinterpreted in 31.2% of cases.2 12
Features associated with increased sensitivity and specificity of detection of perineural spread are:
- Increase in the nerve size or replacement of perineural fat with tumour
- Widening or excessive enhancement within the
- pterygopalatine fossa
- vidian canal
- foramen rotundum
- Expansion or abnormal enhancement of the cavernous sinus.2
In this patient, the trigeminal neuralgia is explained by tumour spread from the maxillary antrum along the maxillary nerve to the pterygopalatine fossa and trigeminal ganglion.7 13
The facial flushing can be accounted for by tumour infiltration of the postganglionic sympathetic fibres that supply the facial sweat glands and travel via the trigeminal nerve branches.14 15
The cavernous plexus supplies branches to the third nerve via the ophthalmic artery which supply the Muller's superior palpebral muscles.14
The ptosis can be explained by the tumour located where the internal carotid plexus forms lateral to the artery or by retrograde tumour spread from the pterygopalatine ganglion.14
The dilated pupil could be due to interruption of the pre or post-ganglionic parasympathetic fibres at the cillary ganglion10
due to tumour spread from the pterygopalatine ganglion via the zygomaticotemporal nerve to the orbit14
or be damaged at the cavernous sinus.15
The lack of lacrimation can be explained by interruption of the parasympathetic supply to the lacrimal gland at the pterygopalatine ganglion, the deep petrosal nerve at the foramen lacerum or the vidian nerve in the vidian canal.14 15
This case describes ophthalmic signs and symptoms resulting from perineural spread of a rare tumour. It shows how history and examination findings can be closely related to anatomical pathology.
- Adenoid cystic carcinoma often presents with a non-specific insidious onset with slow growth.
- Perineural tumour spread can be missed on imaging.
- Perineural tumour infiltration should be a differential diagnosis for unusual neurological presentations.
- Examination findings can be closely related to anatomical pathology.