Metastatic Salivary Ductal Carcinoma to the Mastoid Segment of the Facial Nerve

Salivary duct carcinoma presenting with unilateral multiple cranial nerve lesions and concurrent intracranial metastasis: A case report

RATIONALE

Salivary gland ductal carcinoma (SDC) is a rare malignant tumor of the head and neck, accounting for 1% to 3% of salivary gland malignancy. SDC usually occurs in parotid gland, has a high malignancy degree, poor prognosis, and is prone to distant metastasis. In particular, intracranial metastasis accompanied by multiple cranial nerve lesions is very rare, and early diagnosis is difficult, which easily leads to missed diagnosis and misdiagnosis. Therefore, the diagnosis and treatment of SDC face major challenges. We report a unique case of SDC, which initially presented with progressive facial paralysis followed by progressive intracranial metastases and multiple cranial nerve lesions. After surgery and pathological examination, SDC was finally diagnosed.

PATIENT CONCERNS

A previously healthy 53-year-old male with persistent facial paralysis gradually developed symptoms of ipsilateral multiple cranial nerve lesions, and was hospitalized 8 months after onset.

DIAGNOSES

Brain magnetic resonance imaging enhancement showed multiple irregular intracranial T1 and T2 with uneven signal intensity. Brain computed tomography showed intracranial space-occupying lesions, the largest of which was about 55 × 42 × 38 mm, with extensive bone destruction. Pathological findings showed malignant cell mass in the left temporal lobe tumor. Immunohistochemical: (++), CK7(+++), AR(++), Brg-1(+), Her-2(2+), Ki67(+, approximately 80%), consistent with high-grade ductal carcinoma, considering salivary gland origin. The final diagnosis was SDC.

INTERVENTIONS

The space-occupying lesions in the left cavernous sinus region and temporal lobe were partially resected. Local radiotherapy was recommended, but the patient refused.

OUTCOMES

Postoperative symptoms did not improve significantly. Follow-up after 4 months showed no improvement in the extensive cranial nerve lesions on the left side.

LESSONS

In clinical practice, in the face of persistent facial palsy symptoms that gradually spread to other cranial nerves, the possibility of secondary facial nerve injury and malignant salivary gland tumors, especially SDC, cannot be easily ruled out even if imaging studies do not reveal any space-occupying intracranial lesions. Through the comprehensive use of imaging, pathology and immunohistochemistry and other diagnostic methods, the early detection and accurate diagnosis of SDC can be achieved, so as to provide the best treatment strategy for patients and improve the prognosis.

A Case of Salivary Duct Carcinoma Intracranial Invasion due to Perineural Invasion Through the Facial Nerve

BACKGROUND

Salivary duct carcinoma (SDC) is a rare parotid tumor that often develops as a rapidly growing mass with a poor prognosis. It has a high rate of distant metastases, sometimes with infiltration along nerves. We describe a case of SDC that originated outside the cranium and extended into the cranium along the path of the facial nerve.

CASE DESCRIPTION

A 74-year-old man underwent magnetic resonance imaging at a local hospital, which revealed a tumor in the left internal acoustic canal; the patient was referred to our department. A left facial schwannoma was suspected, and magnetic resonance imaging was performed again 6 months later. Rapid tumor growth was confirmed, and the tumor was resected. The tumor displayed atypical epithelial cells with comedo necrosis and cribriform structure and was diagnosed as SDC. All residual intracranial tumors were removed using the middle fossa approach. The tumor, which was considered to be a primary tumor, was found near the stylomastoid foramen, and it was removed with the parotid gland. Five months after the initial surgery, metastasis to the trigeminal nerve was observed, and this was removed using a retrosigmoid approach, followed by radiation therapy.

CONCLUSIONS

All 4 surgical specimens of this case were presented, and the path of tumor progression was examined in detail. Although the primary lesion was small, intracranial invasion along the facial nerve occurred. SDC should be considered as a tumor that can extend into the cranium, even with a small primary lesion.