NECK, LARYNX, AND THYROID

WADE WONG, D.O.

Hypopharynx

Hypopharynx includes the pyriform sinuses, the post-cricoid area, the posterior pharyngeal wall above the cricoid to the vallecula and to the pharyngo esophageal junction.

Malignancies in this region: Squamous cell cancer and rarely minor salivary gland malignancies (adenoid cystic carcinoma).

Most common site of malignancy: Pyriform sinuses.

Pyriform sinus cancers are extremely invasive with a high rate of metastasis to adjacent lymph nodes.

Up to fifty percent of patients have positive nodes at time of presentation.

Other sites of involvement by a hypopharyngeal malignancies include the post cricoid and post pharyngeal regions.

Early bilateral extension is common.

Malignancies in hypopharynx also have high propensity for deep spread to posterior lateral soft tissues and also down into the larynx.

Except for inflammatory conditions there are very few benign processes of the hypopharynx.

Larynx

Anatomy:

Supraglottic larynx (vestibule) above the laryngeal ventricle. Includes the false cords and aryepiglottic folds.

Laryngeal ventricle: Dividing line between true and false cords.

True cords (glottis). Extends from arytenoid cartilages to anterior commissure of the thyroid cartilage.

Benign Masses of the Larynx:

Laryngocele

Outpouching of laryngeal ventricle secondary to obstruction of the laryngeal saccule.

May be air filled or water filled.

Common in musicians who play wind instruments but could be secondary to obstruction by carcinoma.

Inflammatory Lesions

Laryngitis: Associated usually with viral upper respiratory tract infections.

Epiglottitis: Possibly life threatening and not uncommonly seen in young children. Usually caused by hemophilus influenzae.

Croup: Viral etiology in very young children and infants. Edema of the glottis and subglottis.

Papillomas

Benign neoplasm that has the potential for malignant transformation.

Usually found on the true cords.

Malignant Neoplasms of the Larynx

Supraglottic Squamous Cell Carcinoma

Because of voice saving procedures and the indications for supraglottic laryngectomy as opposed to total laryngectomy it is important to evaluate the presence of transglottic spread (crossing the laryngeal ventricle). Tumor that extends to or below the laryngeal ventricle to the glottis usually requires a total laryngectomy. Also, if there is cartilaginous, postcricoid, or anterior commissure invasion a voice saving supraglottic laryngectomy cannot be performed.

Unfortunately, abundant lymphatics in the supraglottic and hypopharynx lead to very early lymph node metastasis.

T - Staging for Supraglottic Cancer

T1: Limited to one sub site. Normal cord mobility.

T2: More than one sub site with normal cord mobility.

T3: Cord fixation and/or invasion of post cricoid area, piriform sinus, preepiglottic tissues.

T4: Invasion through thyroid cartilage and/or extension to tissues beyond larynx.

(Sub sites: false cords, arytenoids, suprahyoid, epiglottis, infrahyoid epiglottis, area epiglottic folds).


Glottic Squamous Cell Cancer

Voice saving vertical hemi-laryngectomy may still be possible if the cancer is confined to only one vocal cord without extension.

Other lesions may mimic squamous cell cancer and invade the larynx, and these include thyroid cancer as well as chondroid tumors from the adjacent thyroid cartilage.

T - Staging of Glottic Cancer

T1: Limited to vocal cords. Normal mobility.
T1A: Limited to one vocal cord.
T1B: Limited to both vocal cords.
T2: Extends to supraglottis and/or subglottis and/or vocal cord mobility.
T3: Limited to larynx with vocal cord fixation.
T4: Invasion through thyroid cartilage and/or extra laryngeal extension.

Minute mucosal surface lesions may be difficult to discern on imaging, and this is often better done by the endoscopist. However, the job of the diagnostic radiologist is one of determining deep spread. Pay particular attention to:

Laryngeal cartilage invasion.

Transglottic extension.

Extra laryngeal extension.

Extension into adjacent fascial spaces in a vertical manner. These include parapharyngeal space and carotid space.

Regional lymph nodes including internal jugular chain of nodes and the midline delphian node.

Be observant for possible lung metastasis or secondary lung primary.

Needle biopsy of suspicious deep masses may be necessary under imaging guidance.

Thyroid Gland

Anatomy: Thyroid gland is situated anterior to the trachea and has two lobes with a possible variable pyramidal lobe projecting upwards from the isthmus.

The diseases of the thyroid are most often evaluated by radio-nuclide imaging and ultrasound. Occasionally CT and MR incidently delineate masses of the thyroid.

Benign Masses of the Thyroid

Adenomas

Comprise about seventy percent of solitary nodules.

Margins of adenomas are usually well delineated.

Adenomas may be either follicular or papillary and may be calcified.

Difficult to differentiate benign adenomas from carcinomas of the thyroid by imaging. Biopsy may be necessary.

Goiters

Diffuse enlargement of the thyroid gland.

Often found in association with iodine deficiency.

May be multinodular with areas of cystic degeneration, hemorrhage, or colloid formation.

Usually evaluated by nuclear studies.

Colloid Cyst

Common thyroid abnormality.

Cold nodule on nucs, cystic on ultrasound.

May have high signal with the T1 weighted MR images.

Malignant Neoplasms of the Thyroid

Thyroid Cancer

Eighty percent are papillary, follicular, or mixed.

Ten percent medullary.

Three percent anaplastic.

Medullary thyroid carcinomas may be associated with multiple endocrine neoplastic syndromes (MEN II, A and B) involving possible parathyroid abnormalities, pheochromocytoma, and other manifestations.

Papillary carcinomas tend to spread by lymphatic means and often occur in young patients under the age of forty.

Follicular carcinomas tend to spread hematogenously.

Non-Hodgkin's Lymphoma

May present as a solitary nodule or diffuse enlargement of the thyroid.

With or without associated large lymph nodes and expansion of Waldeyer's Ring.

May arise extremely rapidly.

Metastasis to the Thyroid

Especially lung, breast, renal.

Parathyroid Glands

Usually located to the thyroid. Usually there are four glands. Sometimes they are located atypically in the upper mediastinum or in the thyroid gland.

Pathology: Parathyroid cyst. Parathyroid adenomas.

Diagnosis: Ultrasound, CT, MR. Good luck. They are tough to find.

Other Neck Masses

Schwannoma

Well encapsulated masses usually found in the anterior lateral neck or in the posterior lateral oral pharynx or nasal pharynx.

Often associated with cranial nerves 9, 10, 11. Most commonly arise from cranial nerve 10 in the neck.

Carotid space location for cranial nerve 10. Nerve runs behind the carotid and tends to bow the carotid anteriorly.

With contrast schwannomas may have low signal center probably due to collagen content.

If schwannomas are multiple, consider the possibility of underlying neurofibromatosis type II (bilateral 8th nerve schwannomas).

Neurofibromas may be indistinguishable from schwannomas when imaged.

Paragangliomas:

Often found at the skull base (glomus tympanicum, glomus juglare) but can be found along the vagus nerve (glomus vagale) as well as at the carotid bifurcation. (Carotid body tumor).

Those found at carotid bifurcation tend to splay the crotch of the common carotid artery.

Tend to be extremely vascular, and one may see numerous flow voids (salt and pepper appearance particularly on T2).

Embolization often helpful prior to removal.

Lipoma

Benign well encapsulated fat containing tumors usually in the subcutaneous or submucosal regions.

Commonly found in the posterior triangle and are very common in obese women.

Can arise in the parapharyngeal space.

Can cause compression of adjacent structures.

Can also be mistaken for other masses on physical examination such that imaging can be extremely to differentiate them from other malignant processes.

Liposarcomas

Relatively rare malignancies.

Usually quite low grade.

Arise from lipoblasts and not preexisting lipomas.

Contain fat and soft tissues (sarcomatous) elements but may have more soft tissue signal characteristics than fatty signal characteristics when imaged due to predominance of sarcomatous elements.

Branchial Cleft Cyst

Probably most common congenital cystic neck mass.

Often found in age groups ranging from teens to forties.

Often noticed when they become infected.

Usually located at anterior lateral neck just under the sternocleidomastoid muscle.

Common location is actually at the angle of the mandible.

Usually arise from second branchial cleft.

Can be located as far inferiorly as the supraclavicular level.

If cyst is found in the external ear canal or parotid gland, this most likely represents a first branchial cleft cyst.

Branchial cleft cysts are generally unilocular and thin walled unless they become infected.

Sebaceous Cyst

Can be quite large and may have mixed signal characteristics depending upon composition.

Thyroglossal Duct Cyst

Usually midline or slightly off midline.

May be located from thyroid gland up to foramen cecum at the base of the tongue.

Unilocular.

Painless, found in the adult.

Most commonly infrahyoid (65%), less commonly superhyoid.

May have high signal on T1 due to high protein content.

Cystic Hygromas and Lymphangiomas

Non-encapsulated lesions arising from primitive lymph tissue.

Probably represent a sequestration of primitive lymph sacs.

Tend not to enhance.

Soft and compressible and usually do not exhibit much mass effect.

Appear to be invaginating around and between structures.

Can become hemorrhagic.

Usually multi-loculated.

May present as painless mass posterior to the sternalclydoidmastoid muscle particularly in the neonate.

Often high signal on T1 due to blood, protein, or fat content.

Lymphangiomas tend to have small vascular type of channels and may be associated with adjacent vascular structures.

Cystic hygromas tend to be larger fluid filled sacs.

Abscesses

Usually present as thick walled, rim enhancing masses with central fluid.

May have areas of additional enhancement (cellulitis) and edema.

Obliteration of adjacent fat planes due to cellulitis is common.

Often related to tonsillitis.

Increasingly found with intravenous drug abuse.

Increase in incidence of abscesses adjacent to the jugular vein (related to IV drug abuse access to the jugular vein).

Other Cystic Masses

Dermoids usually supraglottic, usually midline, may contain fat.

Teratoma often mid-line and may have calcification.

Hemangioma

Most common neck mass in kids.

May affect oral pharynx and face as well as neck.

Cavernous type is the most common.

Check for phleboliths on CT.

May have bright signal on T2 due to slow flow.

May present as a solid mass with diffuse enhancement.

AVMS and AV Fistulas

May present with unusual flow voids, vascular channels, or bright areas of slow flow in venous portions.

Fibromatosis (Desmoid)

Well defined area of fibrosis, locally infiltrating.

Most common in superclavicular area.

May be infiltrative with distortion of fat planes.

May appear extremely malignant and be locally aggressive to the point of a low grade fibrous sarcoma.

Fibromatosis Coli

NKA sternocleidomastoid muscle mass of infancy or wry neck.

Due to birth trauma resulting in compartment injury of sternocleidomastoid muscle with hemorrhage and fibrosis.

Leads to torticollis.

Should resolve by age two spontaneously.

Other Malignant Tumors of the Neck

PNET (Primitive neuro ectodermal tumor): May arise in the soft tissues or from the neural elements adjacent to the spine and may represent a rather large mass particularly in children.

Rhabdomyosarcoma. Head and neck is second most common place for this lesion in children. Often found in the orbital and masticator regions however may extend into the neck regions.

Metastasis: Lung, breast, renal, melanoma.

Vascular Lesions

Thrombosis of jugular vein.

Calcification of the carotid/carotid aneurysm, arteriosclerotic disease.

Post Surgical/Post Radiation Changes

Post surgical muscle and fat flaps may be rather confusing at times. Not uncommonly there is loss of the sternocleidomastoid muscle with radical neck surgery. Biopsy may be necessary to distinguish rather recurrent tumor or post surgical flap residuum with scarring as present.

Post radiation changes may also be difficult to determine from recurrent tumor. Follow-up films and/or biopsy may be necessary. The role of CT or MR is not to specify the type of cancer but rather to define the extent of the tumor and to reveal important areas of tumor spread.

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