Parotid Tumors Flashcards
Benign parotid Gland Tumors - distribution/percentages of the total of all parotid tumors.
- Pleomorphic adenoma 45%
- Warthin’s tumor 6.5%
- Benign cyst 1%
- Lymphoepithelial lesions 0.6%
- Oncocytoma 0.7%
- Monomorphic adenoma 0.2%
Malignant parotid gland tumors - distribution/percentage of the total of all parotid tumors.
- Mucoepidermoid carcinoma 15.7%
- Adenoid cystic carcinoma 10%
- Adenocarcinoma 8%
- Malignant mixed tumor 5.7%
- Acinic cell carcinoma 3%
- Epidermoid carcinoma 1.9%
- Other (Anaplastic) 1.3%
Myoepithelial Carcinoma of the Salivary Glands
1) Uncommon tumor of the salivary glands of adults with peak incidence in the mid 6th decade of life
2) Most common site of occurrence = Parotid gland
3) Presentation:
- Asymptomatic mass present for months to years, may have associated pain and bone destruction
- May develop in association with a pleomorphic adenoma with longstanding mass with recent rapid increase in size
- May be a myoepithelial carcinoma ex pleomorphic adenoma or may develop from a preexisting myoepithelioma
4) Etiology - unknown
5) DDx:
- Myoepithelioma
- Epithelial-myoepithelial carcinoma
- Clear cell adenocarcinoma of the salivary glands
- Sarcoma: synovial sarcoma, malignant peripheral nerve sheath tumor, leiomyosarcoma, spindle cell squamous carcinoma and metaplastic carcinoma, metastatic malignant melanoma, plasmycytoma
6) Treatment: Complete surgical excision is treatment of choice and includes -
- Parotid gland: superficial parotidectomy
- Submandibular gland: glandectomy
- Minor salivary glands: WLE with tumor free margins
- In the presence of osseous invasion, a more radical excision is required
- In the absence of neck dz, no neck dissection is warranted
- XRT may be used, but effectiveness is uncertain
- Chemotx - not proven
7) Behavior of these tumors is variable: some are indolent, and some are aggressive
- 50% of patient’s develop mets: lung is most common site of mets; distant mets more frequent than local/regional mets
- 50-67% develop recurrent tumor, often multiple recurrences
- 30% of patient’s die of dz
How do you find the facial nerve in parotid surgery? What are the surgical landmarks?
1) Tympanomastoid suture line - the nerve is medial to this landmark (this is my go-to method)
2) Posterior belly of the diagastric muscle - the nerve is approximately 1 cm above and parallel to the upper border of the posterior diagastric muscle above the transverse process of the atlas, lateral to the styloid process near the insertion of the digastric muscle at the mastoid tip. Note: the facial nerve never crosses the digastric mscl - you can dissect on its lateral surface safely
3) Trace a peripheral branch of the facial nerve back to the pes anserinus - usually the marginal mandibular nerve or a buccal branch of the facial nerve
4) Find the facial nerve in the mastoid (must do a mastoidectomy) and follow the nerve out through the stylomastoid foramen to the pes anserinus
5) Tragal pointer - the facial nerve is 1 cm deep and inferior to the tragal pointer in the general area of the junction of the external ear canal, the mastoid tip, and the posterior belly of the digastric muscle. The facial nerve will never be encountered prior to reaching the tragal pointer
How to avoid complications in Parotidectomy/how to avoid inadequate parotid surgery.
1) Do not start a parotidectomy without availability of frozen section pathologic review
2) Always be prepared to perform a total parotidectomy, neck dissection, and extended operation when you start the operation - be prepared to perform the type of operation that is necessary for complete removal of the tumor.
3) Do not feel assured that a parotid mass is benign solely on the basis of an FNA biopsy
4) Be prepared to address facial nerve deficits at the time of the initial operation
5) Careful preoperative assessment of the extent of the tumor is essential to plan the extent of extirpation and reconstruction of the resulting defect.
What are the indications for Extracapsular Parotidectomy?
1) Benign preoperative FNA biopsy
2) Tumor less than 4cm in diameter
3) Parotid mass that is mobile on physical exam
4) Peripheral location in the parotid gland
5) No worrisome intraoperative features
- No Fibrosis
- No invasion into surrounding structures
What are the contraindications to extracapsular parotidectomy?
1) Malignant preoperative FNA biopsy
2) Preoperative facial weakness/paralysis
3) Deep lobe location
4) Concerning clinical features
- Fixation
- Skin involvement
- Irregular borders on imaging
What are the potential complications associated with parotid surgery?
1) Facial nerve weakness/paralysis
2) Sialocele
3) Cheek and ear numbness
4) Frey’s syndrome (Gustatory sweating)
5) Tumor rupture and wound seeding
What are the indications for a total parotidectomy?
1) High grade malignant tumors with a high risk for metastasis
2) Any parotid malignancy with an indication of having metastasized to intraglandular or cervical lymph nodes
3) Any primary parotid malignancy that originates within the deep lobe.
When should the facial nerve be resected in parotid surgery?
1) If the facial nerve is involved with tumor, it should be resected to negative margins
2) In general, if the preop facial nerve function is fully intact, the facial nerve most likely has not been invaded and all attempts should be made to preserve it.
3) If the patient has a paralyzed or paretic facial nerve preoperatively, it is likely invaded by the tumor and should be resected. The extent of the resection should be dictated by intraoperative frozen-section biopsies and should proceed until proximal and distal margins are deemed to be negative.
Management of the Node-negative neck in parotid surgery.
1) Treatment of the neck should be performed only in selected patients with tumors that have poor prognostic features for metastasis
2) Tumors of the submandibular gland have a significantly higher incidence of occult metastasis to the cervical lymph nodes (21%) than those of the Parotid gland (9%)
3) The size of the primary tumor and the presence of extra glandular extension are also correlated with risk of metastasis.
- Tumors > 4cm have a 20% risk of occult metastasis compared with a 4% risk associated with smaller tumors
4) Extraparotid tumor extension is among the most predictive variables associated with occult lymph node metastasis
5) Patients with high T stage (T3 and T4) tumors should undergo routine neck dissections, even if they do not have clinical evidence of cervical lymph node metastasis
What factors are associated with occult metastases and/or poor prognosis in salivary gland tumors?
1) Primary tumor site: Tumors of the submandibular and sublingual glands tend to metastasize more frequently than those of the parotid gland
2) Primary tumor size and extraglandular extension: T3 and T4 tumors tend to have a higher incidence of occult metastases and worse outcome
3) Age: Patients > 50 years have worse outcomes
4) Presenting symptoms: Facial nerve paralysis and pain are associated with lymph node metastasis
5) Histologic type/grade: Neoplasms with higher incidence of nodal metastases and poorer prognosis include high-grade mucoepidermoid carcinoma, undifferentiated carcinoma, squamous cell carcinoma, high-grade (solid-type) adenoid cystic carcinoma, high-grade adenocarcinoma not otherwise specified, salivary duct carcinoma, and any tumors with “high-grade transformation.”
6) Local tissue invasion: Perineural invasion and local bone invasion portend shorter disease-free and overall survivals.
7) Positive resection margins: Associated with worse locoregional control and lower survival rate.
8) High Ki-67 Expression: Associated with shorter disease-free survival in adenoid cystic and mucoepidermoid carcinoma.
9) Her2 (ERBB2) Overexpression: Associated with shorter disease-free survival in salivary duct and mucoepidermoid carcinoma.
What are the indications for adjuvant radiation therapy to the primary site in salivary gland tumors?
1) Advanced stage
2) Positive margins following resection
3) High-grade histologic types:
- Squamous cell carcinoma
- Undifferentiated carcinoma
- Small cell carcinoma
- High grade mucoepidermoid carcinoma
- Carcinoma ex pleomorphic adenoma
- High-grade adenocarcinoma not o/w specified
- Salivary duct carcinoma
- Carcinomas with high-grade transformation or dedifferentiation
4) Local tissue invasion; perineural or bone invasion
5) Patients with high-risk features should receive adjuvant radiation therapy.
- High risk features include positive margins and extracapsular extension
Management of the Node Negative Neck in Salivary Gland Tumors - Bottom Line:
1) Patients with high T stage (T3/T4) tumors should undergo routine neck dissections, even if they do not have clinical evidence of cervical lymph node metastasis
2) Elective treatment of the neck is indicated in patients with high-grade histologic tumor types, such as adenocarcinoma, SCCA, and high-grade subtypes such as high-grade MEC
3) Controversy - some authors recommend that an ipsilateral neck dissection should be performed on all patients with salivary gland malignancies, regardless of histologic stage or type
What type of neck dissection should be performed in patients with salivary gland malignancies?
1) A selective neck dissection is considered the treatment of choice
2) The levels of the neck to be dissected are determined by the site of the primary tumor
- Parotid tumors: dissect Levels I through IV
- Submandibular and sublingual malignancies: dissect levels I - III
3) Caveat: if occult disease is detected in the first-echelon dissection for either parotid or submandibular primary malignancies, a comprehensive neck dissection is recommended
