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Endoscopic Resection of a Sinonasal Adenoid Cystic Carcinoma Involving the Anterior Skull Base
Dan Jethanamest
Satish Govindaraj MD
Noam A. Cohen MD, PhD
Alexander G. Chiu MD
Introduction
The term "cylindroma" was first used to describe the histologic appearance of adenoid cystic carcinoma by Billroth in 1859. Adenoid cystic carcinoma is a relatively uncommon tumor that has a slow but progressive course. It represents less than 1% of all malignancies in the head and neck and is most commonly associated with the minor salivary glands (60%). Adenoid cystic carcinoma accounts for 5-15% of all paranasal sinus malignancies.
Case
A 67 year-old man was referred to our institution with left middle meatal polyps. A CT scan revealed a left sided nasal mass with erosion of the superior nasal septum and abutment of the mass to the skull base. Given the erosive nature of this lesion, a biopsy was performed in the office and was read with a differential diagnosis of adenocarcinoma versus a primary salivary gland tumor. A fine cut CT scan was ordered which showed evidence of a left nasal mass that eroded through the superior nasal septum and abutted the cribiform plate on the left as well as the right nasal cavity. A MRI of the brain and orbits revealed no evidence of intracranial extension or dural enhancement. An endoscopic resection of the tumor was planned, with resection of the bony anterior skull base and dural biopsies to rule out intracranial involvement.
The patient had a lumbar drain placed prior to the operation and 0.1 cc of 10% IV fluorescein dye was injected into the intrathecal space. The tumor was found to arise from the left superior nasal septum and middle turbinate with superior extension to the cribiform plate bilaterally. The tumor was debulked with a microdebrider to visualize its point of attachment at the superior nasal septum and middle turbinate. Complete resection was performed including a complete left sphenoethmoidectomy, superior septectomy, transseptal frontal sinusotomy, and resection of the lamina papyracea and anterior cribiform plate. Multiple tumor margins were taken including underlying dural and periorbital biopsies which were negative for tumor. Multiple CSF leaks were created following the dural biopsies and a multi-layered temporalis fascia graft, fibrin glue and microfibrillar collagen packing was used to reconstruct the skull base. A Merocel(r) sponge was placed to support the packing and two nasal trumpets were placed to divert airflow from the nasal cavity. The patient's postoperative course was uneventful with removal of the lumbar drain postoperative day 2 and discharge postoperative day 6 after removal of the nasal trumpets. Three months following surgery he is receiving radiation therapy to the skull base and has no evidence of residual or recurrent disease.
Discussion
Adenoid cystic carcinoma (ACC) is a slow growing but progressive disease that is difficult to effectively treat. The tumor frequently recurs locally, has a tendency for perineural spread, and can metastasize distantly, making cure elusive although patients may often live extended time periods even with metastatic disease.
Radiographically, these tumors should be evaluated by both CT and MRI. Since ACC has a predilection for perineural spread, MRI should be part of the preoperative evaluation. On T1-weighted imaging, these neoplasms most often have an intermediate signal intensity, while T2 can be variable depending upon the cellularity of the tumor. Lesions with greater cellularity tend to produce intermediate signal, while less cellular tumors, with greater stromal areas, appear hyperintense. Signs of perineural spread include: nerve enlargement, irregularity or enhancement; loss of the high T1 signal of fat pads surrounding nerves in their foramina; and muscle denervation.
In the paranasal sinuses and nasal cavity, adenoid cystic carcinoma is treated with a combination of complete surgical resection and adjuvant radiotherapy. Naficy has reported an overall survival rate of 73% in sinonasal ACC treated with surgery and adjuvant radiation therapy. Although aggressive treatment is recommended, the natural course of this process described as indolent with late recurrence has not been altered by present treatment modalities.
Sinonasal malignancies extending to the anterior skull base present unique challenges for treatment due to the limits of anatomical exposure and sensitivity of surrounding structures. The endoscopic resection of sinonasal malignancies is an evolving area as endoscopic instrumentation and surgical experience matures. A review of 47 patients treated by an endoscopic approach by Roh et al. at the Cleveland Clinic and the University of Pennsylvania found that local recurrence, overall survival, and disease-free survival in their cohort compared favorably to published rates for patients undergoing anterior craniofacial surgery.
This tumor's location and confinement to the sinonasal compartment made endoscopic resection an ideal choice for treatment with the least morbidity. Due to this disease's natural history, long term follow up for both local and distant metastases must be performed.
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