Non-Neoplastic Lesions of the Pharynx

Embryology and Anatomy

• Rathke pouch is an ectodermally derived outpocketing arising from the roof of the primitive oral cavity lying superior to the buccopharyngeal membrane that develops around the third week of gestation and grows toward the brain.

• Rathke pouch ultimately forms the anterior lobe of the pituitary gland.

• By the fifth week of gestation, this pouch has elongated and become constricted at its attachment to the oral epithelium and comes into contact with the infundibulum, which ultimately develops into the posterior lobe of the pituitary gland.

• The posterior part of Rathke pouch develops into the pars intermedia:

  • Lumen between the anterior lobe and the pars intermedia gradually obliterates; however, if the lumen does not close, a cleft is formed (Rathke cleft) that may become cystic, developing a Rathke cyst.

Clinical

• Rathke pouch cyst represents approximately 2% of all lesions of the sella turcica.

• Typically, Rathke pouch cyst is an asymptomatic, congenital lesion that is incidentally found in routine autopsies.

• Symptomatic cysts occur but are uncommon:

  • Symptomatic cysts are more common in women than in men and occur over a wide age range but are most common in the fourth decade of life.

  • Symptoms include headaches, visual disturbances, nausea, vomiting, pituitary-related abnormalities, including galactorrhea, amenorrhea, diabetes insipidus, acromegaly, and meningeal irritation.

  • Sudden onset of severe headache or sudden increase in headache severity may occur and has been associated with hemorrhage into the cyst, a presentation that mimics the clinical syndrome of pituitary tumor apoplexy, leading to the designation of Rathke cleft cyst apoplexy.

  • Increased serum prolactin has been reported in Rathke pouch cysts.

  • Rare association with Klinefelter syndrome has been reported.

  • Hybrid lesions, including Rathke cleft cyst and pituitary adenoma, have been reported.

• Radiology:

  • Well-circumscribed, round, or lobulated intrasellar mass:

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      Wall of cyst is generally thin.

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      Cyst content usually similar to cerebrospinal fluid

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      More complex cysts show increased density with septa partitioning the cystic portion.

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      Most lesions have intrasellar and suprasellar components although lesions confined to the sella turcica can be found, as well as suprasellar lesions and intrasphenoidal lesions may occur.

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      Usually lacks associated calcifications:

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        Absence of calcifications assists in differ­entiating a Rathke pouch cyst from a craniopharyngioma; craniopharyngiomas are characterized by the presence of calcifications.

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        Rare examples of Rathke pouch cyst may be associated with mineralization.

Pathology

Differential Diagnosis

• Rathke pouch cyst, which is localized to the area of the sella turcica, contrasts to Tornwaldt cyst located in the posterior pharynx.

Treatment and Prognosis

• Drainage of the cyst with partial removal of the cyst wall (for diagnosis) via a transsphenoidal approach is the preferred treatment.

• Endoscopic endonasal resection used as a safe and effective approach in treatment

• 5% recurrence rate has been reported.

Embryology and Anatomy

• Pharyngeal bursa is a sac-like depression on the posterosuperior nasopharyngeal wall that forms around the sixth week of gestation when the cephalic portion of the notochord comes into close contact with the foregut:

  • Contact between the pharynx and the notochord is usually transient but may persist in adults, in whom the pharyngeal respiratory epithelium may grow, creating a potential space that may be walled off, creating the Tornwaldt cyst.

Clinical

• Tornwaldt cyst is uncommon.

• No gender predilection

• These cysts may occur at any age, although most are diagnosed in the second to fourth decades of life.

• They may be asymptomatic, but when infected, symptoms include drainage into the nasopharynx of purulent material; in addition, symptoms may include headaches, otalgia, and fullness of the ear, halitosis, and neck soreness or stiffness.

• Cysts are located in the midline of the posterior nasopharyngeal wall but may be found slightly off midline:

  • Usually extends upward and backward toward the occipital bone

  • Tornwaldt cyst lies caudal to the location of Rathke cleft cyst.

• Endoscopic appearance of these lesions is that of a submucosal, firm, and smooth mass; adjacent mucosa may be erythematous.

• Radiology:

  • Appear as a mass high on the posterior nasopharyngeal wall; air may be seen in the tract extending from the midline posterior nasopharynx toward the occipital tubercle.

  • On CT scan, the cyst may contain fluid of similar density as cerebrospinal fluid and does not enhance after contrast; calcifications may be identified.

Pathology

Differential Diagnosis

• Rathke pouch cyst, which is localized to the area of the sella turcica, contrasts to Tornwaldt cyst located in the posterior pharynx.

Treatment and Prognosis

• Surgical excision is the preferred treatment; incomplete excision will result in recurrence.

• Antibiotic therapy is used preoperatively for patients with infected cysts.

Clinical

• Uncommon lesion

• Reports of nasopharyngeal hamartomas are often included with nasal hamartomas, so a true incidence of hamartomas exclusively limited to the nasopharynx cannot be determined.

• No gender predilection; occur in adults and in children

• In adults, the clinical presentation may include nasal obstruction, difficulty breathing, post-nasal drainage, and epistaxis.

• In pediatric patients, the clinical presentation may include noisy breathing, stridor, feeding difficulties, and transient cyanosis.

Pathology

Histology

• May be composed of epithelial and/or mesenchymal components:

  • Epithelial hamartoma:

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      Minor salivary gland elements (seromucous glands, ducts, acini)

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      Epithelium (squamous and columnar cells)

  • Mesenchymal components:

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      Blood vessels, lymphoid tissue, fibrous stroma

• Metaplastic components such as bone may be present.

NOTE: The epithelial hamartomas may be histologically identical to the respiratory epithelial adenomatoid hamartoma and seromucinous hamartoma of the sinonasal tract (see Section 1 for more complete discussion).

Differential Diagnosis

• Teratoma

• Epithelial neoplasms:

  • Adenocarcinoma

  • Papilloma, carcinoma

• Mesenchymal neoplasms:

  • Hemangioma, angiosarcoma, others

Treatment and Prognosis

• Simple excision is curative.

Clinical

• Rare lesion that may occur in association with congenital anomalies

Pathology

Treatment and Prognosis

• Simple excision is curative.

Clinical

• Predilection for female infants with majority of the cases occurring in the infantile period

• Symptoms include difficulties in breathing, swallowing, or sucking.

• May arise in other areas of the pharynx including oropharynx, as well as in association with the eustachian tube and the middle ear

Pathology

Differential Diagnosis

• Teratoma:

  • Absence of endodermally derived tissue and absence of the wide variety of tissue types usually seen in teratoma will allow for distinguishing these lesions.

Treatment and Prognosis

• Simple surgical excision is curative.

Clinical

• Uncommon lesion

• No gender predilection; occur over a wide age range from the first decade to the seventh decade with a mean age of occurrence at 25 years

• Clinical presentation includes dysphagia, sore throat, and the sensation of a mass lesion in the throat:

  • Symptoms may be present from a few weeks to years.

• Majority are of palatine tonsil origin but occasionally may originate from the nasopharynx or from the nasopharyngeal tonsil (i.e., adenoids):

  • Unilateral lesions without side predilection

• Clinical examination, many of these lesions are felt to be neoplasms

Pathology

Differential Diagnosis

• Nasopharyngeal angiofibroma:

  • Occurs in adolescent males

  • Typically presents with epistaxis due to its rich blood supply that often attains large sizes with extensive growth and even bone erosion

  • Histologically have a cellular stroma composed of stellate fibroblasts and staghorn-shaped, thin-walled vascular structures, the latter typically lacking or with an attenuated smooth muscle component

  • Fibroblastic cells are immunoreactive for β-catenin

  • In contrast to nasopharyngeal angiofibromas, the lymphangiomatous polyps may occur in women and tend to have a relatively paucicellular fibrous stroma with a prominent lymphoid component.

• Fibroepithelial polyps

• Papillomas

• Epithelial neoplasms characterized by the presence of an exophytic surface epithelial proliferation of multilayered bland epithelial cells and lacking an associated lymphoid component

• Majority of squamous papillomas lack surface keratin, although occasionally prominent (hyper)keratosis may be identified

• Rare examples of Schneiderian-type papillomas may occur in the pharynx (oro- and nasopharynx), but the histology of the lesions contrast so distinctly from the lymphangiomatous polyps, making differentiation straightforward.

• Lymphangioma:

  • Neoplasm of endothelial-lined lymphatic spaces that are histologically characterized by the presence of widely dilated and irregularly appearing vascular channels, features not usually associated with lymphangiomatous polyps

Treatment and Prognosis

• Simple surgical excision usually in the form of a unilateral tonsillectomy is curative.

Clinical

• Rare lesion with fewer than 20 cases reported in the literature

• Male predilection; usually presents in immediate neonatal period or in early infancy (by age of 6 weeks)

• Symptoms include respiratory distress, nasal airway obstruction, and/or feeding difficulties.

• Often located at or near midline in the naso­pharynx:

  • Uniform midline presentation is a feature in common with other developmental anomalies in the head and neck region, including:

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      Dermoid sinus, nasal glioma, and thyroglossal duct cyst

• Imaging by CT and MRI helpful in determination of size of the mass and relationship to surrounding anatomic structures.

Pathology

NOTE: There is uniformity in the gross and microscopic features from case to case.

Treatment and Prognosis

• Simple excision (polypectomy) is curative.

• No reported recurrences