If paraganglioma remains a differential diagnostic possibility based on the location of the lesion on CT and MRI, then formal endovascular angiography could be performed preoperatively.
Differential Diagnosis
As each of these lesions is very rare, more common processes should fi rst be ruled out. Before consid- ering the diagnosis of a middle ear adenoma or carcinoid, much more common primary or secondary cholesteatomas should be considered. Depending on the location of a middle ear lesion, a glomus tym- panicum paraganglioma may also be in the differential diagnosis.
Other lesions with imaging appearances similar if not identical to that seen with adenocarcinomas include aggressive infl ammatory processes or jugulotympanicum tumors, metastatic disease, or a rare squamous cell carcinoma.
10.1055/978-2-58890-647-2c029_f002
Figure 29–2 A 42-year-old woman with right-sided tinnitus and facial numbness with hoarseness, ataxia, and right-eye diplopia. Limited surgery revealed adenocarcinoma. Axial contrast-enhanced T1-weighted scans through the right temporal bone demonstrate a large enhancing mass involv- ing the right middle ear cleft and petrous tip regions with
additional middle cranial fossa, cavernous sinus and poste- rior fossa extension. As described in the text, these lesions tend to be large at presentation often with extratemporal spread. This patient was treated with limited resection and extensive radiation and continues to do well 12 years later.
106 III MIDDLE EAR AND MASTOID
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Due to the rarity of these lesions and their lack of specifi c associated clinical symptoms and imag- ing features, other more common lesions should always be considered fi rst in a differential diag- nosis. One must rule out metastases (metastatic adenocarcinoma) before diagnosing a primary adenocarcinoma of the temporal bone).Suggested Readings
Dadas B , Alkan S , Turgut S , Basak T . Primary papillary adenocarcinoma confi ned to the middle ear and mastoid . Eur Arch Otorhinolaryngol 2001 ; 258 : 93 – 95
Harnsberger HR, ed. Diagnostic Imaging: Head and Neck. Salt Lake City: Amirsys, 2004
Maintz D , Stupp C , Krueger K , Wustrow J , Lackner K . MRI and CT of adenomatous tumors of the middle ear . Neuroradiology 2001 ; 43 : 58 – 61
Paulus W , Romstock J , Weidenbecher M , Huk WJ , Fahlbusch R . Middle ear adenocarcinoma with intra- cranial extension . J Neurosurg 1999 ; 90 : 555 – 558
Swartz JD, Harnsberger HR, eds. Imaging of the Temporal Bone, 3rd ed. New York: Thieme, 1998 Torske KR , Thompson LDR . Adenoma versus carcinoid tumor of the middle ear: a study of 48 cases and
review of the literature . Mod Pathol 2002 ; 15 : 543 – 555
CHAPTER 30 Adenoid Cystic Carcinoma
Douglas J. Quint
Epidemiology
Twenty-fi ve percent of all salivary gland tumors arise from minor salivary glands, and 50% of minor salivary gland tumors are malignant. The smaller the minor salivary gland, the greater the risk that a tu- mor arising from that gland is malignant. The most common primary minor salivary gland malignancy is adenoid cystic carcinoma. As salivary gland tissue is rarely found in the middle ear (choristomas), it is possible that occasional primary minor salivary gland malignancies will occur in the middle ear. Less than a dozen such primary cases have been reported. Most adenoid cystic carcinomas of the middle ear region secondarily involve the middle ear as a result of cephalad perineural spread of a parotid gland adenoid cystic carcinoma along the seventh cranial nerve into the temporal bone.
Clinical Features
Primary middle ear adenoid cystic carcinoma is so rare that no specifi c clinical features can be de- scribed. As it is considered an aggressive tumor that can invade osseous structures (in this case, the temporal bone), it can be expected to present with pain, seventh nerve dysfunction, and conductive hearing loss depending on its extent. With invasion of the skull base or the intracranial compartment, additional cranial nerve and other symptoms may be present.
Perineural spread by adenoid cystic carcinoma along the facial nerve is often asymptomatic. How- ever, it can present with progressive seventh nerve symptoms and possibly hearing loss depending on the extent of middle ear involvement. An otherwise asymptomatic parotid mass may be palpable.
Pathology
Primary temporal bone adenoid cystic carcinomas are considered a type of malignant ceruminous gland tumor (along with ceruminous adenocarcinomas) that usually arise in the external auditory canal as there is normally no salivary gland tissue in the middle ear. These are very rare tumors in the middle ear region. When they arise in the middle ear region, they are believed to arise from either ec- topic salivary gland tissue (which has been identifi ed in the middle ear region in pathologic studies) or multipotential middle ear mucosal cells (endodermal stem cells).
Treatment
Therapy involves surgery, radiation therapy, or chemotherapy depending on the extent of disease.
Imaging Findings
Primary middle ear adenoid cystic carcinoma is indistinguishable from other aggressive middle ear neoplasms (e.g., squamous cell carcinoma, malignant adenomatous tumors, sarcomas) and some ag- gressive infections. Defi ning the extent of disease determines if surgery is a therapeutic option.
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CT
High-resolution (1 to 2 mm) computed tomography (CT) scanning performed in the axial and coronal planes and reconstructed with a “detail” (bone) algorithm best evaluates the temporal bone region for small soft tissue lesions in the middle ear cleft, facial nerve canal enlargement, and frank osseous destruction. Occasionally, sagittal reformatted images may also prove valuable. If magnetic resonance imaging (MRI) is not available, intracranial, infratemporal, and vascular involvement can be grossly as- sessed by contrast-enhanced CT, but usually such extent of disease is best assessed with MRI and no contrast-enhanced CT imaging is necessary.
MRI
The extent of intraosseous, vascular, intracranial, and extracranial spread by neoplasm, in addition to perineural spread by neoplasm, is best evaluated on multiplanar fat-suppressed T2-weighted and noncontrast and contrast-enhanced T1-weighted MRI. Distinguishing trapped secretions from tumor is also best achieved with MRI. Evaluation of the parotid gland in cases of suspected perineural spread of malignancy is also best done with MRI ( Fig. 30–1 ).
Angiography
If paraganglioma remains a differential diagnostic possibility based on the location of the lesion on CT and MRI, then formal endovascular angiography could be performed preoperatively.
Differential Diagnosis
Imaging features of these very rare tumors are nonspecifi c. Other primary and secondary processes should be considered fi rst in a differential diagnosis. The ultimate diagnosis can only be made patho- logically.
Specifi cally, before considering a primary middle ear adenoid cystic carcinoma, other aggressive neoplastic (e.g., squamous cell carcinoma, malignant adenomatous tumors, sarcomas, metastatic dis- ease, invasive jugulotympanic paraganglioma) or infl ammatory (e.g., chronic otitis) processes should be considered.
When considering a secondary middle ear adenoid cystic carcinoma (e.g., perineural spread from an extratemporal source), other primary temporal bone tumors that can be found along the intratem- poral seventh cranial nerve (e.g., schwannoma, hemangioma) and other neoplasms that can extend perineurally (e.g., squamous cell carcinoma, mucoepidermoid) need to be considered as do infl amma- tory/infectious processes (e.g., idiopathic Bell palsy, herpes zoster) that can affect the facial nerve.
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There are no specifi c clinical or imaging fi ndings to suggest the rare diagnosis of primary middle ear adenoid cystic carcinoma.•
Other middle ear neoplasms (e.g., schwannoma, hemangioma) and infectious processes are much more common than adenoid cystic carcinomas of the temporal bone. In patients with known or previously treated parotid malignancy, perineural extension by neoplasm should always be consid- ered.•
Enlargement of the facial canal by perineural spread of neoplasm may not be accompanied by sev- enth nerve symptoms if the nerve has not yet been invaded by neoplasm.•
Enhancement of the intratemporal seventh nerve without enlargement of the facial nerve canal can represent infi ltration by tumor.108 III MIDDLE EAR AND MASTOID
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Enhancement of the intratemporal portion of the seventh nerve without associated seventh nerve enlargement can represent neoplasm or infection. Follow-up imaging in 3 to 4 months in these patients to assess for interval resolution of the enhancement (which essentially rules out tumor) is suggested before diagnosing a neoplasm.10.1055/978-2-58890-647-2c030_f001
Figure 30–1 A 48-year-old with recurrent adenoid cystic carcinoma extending cephalad from the parotid surgical site into and enlarging the descending portion of the left facial canal. (A) A normal descending facial nerve canal on the right ( dotted arrow ) and an enlarged descending facial nerve canal on the left ( solid arrow ). (B) Noncon- trast T1-weighted MRI (top); contrast T1-weighted MRI (bottom) demonstrates the enhancing neoplasm ( ar- rows ) within the left descending facial nerve canal.
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30 ADENOID CYSTIC CARCINOMA 109
Suggested Readings
Cannon CR , McLean WC . Adenoid cystic carcinoma of the middle ear and temporal bone . Otolaryngol Head Neck Surg 1983 ; 91 : 96 – 99
Harnsberger HR, ed. Diagnostic Imaging: Head and Neck. Salt Lake City: Amirsys, 2004
Morrow TA , Baredes S , Jahn AF , Schulder M . Pathologic quiz case 2. Adenoid cystic carcinoma . Arch Otolaryngol Head Neck Surg 1991 ; 117 : 804 – 805, 807–808
Som PM, Curtin HD, eds. Head and Neck Imaging, 4th ed. St. Louis: Mosby, 2003
Swartz JD, Harnsberger HR, eds. Imaging of the Temporal Bone, 3rd ed. New York: Thieme, 1998 110 III MIDDLE EAR AND MASTOID
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CHAPTER 31 Rhabdomyosarcoma
Douglas J. Quint