Nasopharyngeal cyst of branchiogenic origin: Report of a case and review of the literature.

Abstract

To date, only 22 cases of nasopharyngeal cyst of branchiogenic origin have been reported in the literature. In this article, we report a new case in a 35-year-old woman. We also present a review of the literature and a discussion of the sites of origin, histopathology, and treatment modalities.

Introduction

Congenital cysts of the nasopharynx are rare. When they do occur, there is no specific microscopic feature that conclusively identifies them. However, the specific site in the nasopharynx can provide helpful clues. Embryogenic cysts of the pharyngeal bursa and Rathke's pouch are usually located in the midline, and their histologic features are similar to those of branchial cysts, which are situated laterally in the nasopharynx. What differentiates these internal branchial cysts from other cysts of the first, second, third, and fourth branchial arches is the fact that they form only in the pharynx and they do not produce any neck swelling. The precise embryologic pathogenesis of these cysts is not well understood. To date, only 22 cases have been reported (table 1). [1-14]

In this article, we present a new case of a branchial cyst of the nasopharynx that was located at the lower level in relation to the tonsil and that was successfully treated surgically via the transoral route.

Case report

A 35-year-old woman complained of snoring, mouth breathing, and a persistent right nasal discharge of 5 months' duration. She also reported a 4-month history of decreased hearing and pain in the right ear. Examination revealed a well-circumscribed yellowish mass in the nasopharynx (figure 1). The mass was covered with mucous membrane and dilated blood vessels and was attached to the posterolateral aspect of the nasopharynx on the right side. It extended from the roof of the nasopharynx superiorly to the middle of the right tonsil inferiorly. Medially, the mass crossed the midline; laterally, it was attached to the lateral nasopharyngeal wall posterior to the posterior pillar of the tonsil.

On palpation, the mass was cystic in its consistency. Examination of the right ear revealed a dull and retracted tympanic membrane. Findings on the remainder of the examination were normal. Computed tomography (CT) of the nasopharynx showed that a well-circumscribed low-density mass 3 cm in diameter was attached to the posterior and lateral walls of the nasopharynx on the right side (figure 2). There was no bony erosion. On audiologic investigation, the patient had a conductive hearing loss of 15 dB on the right and a flat tympanogram.

Aspiration of the cyst yielded white opaque material. The 5 x 5-cm cyst was excised under general anesthesia via a transoral approach. Histopathology revealed a branchial cyst lined with stratified squamous epithelium. A submucosal layer contained lymphoid follicles, mono-nuclear inflammatory cells, and goblet cells (figures 3 and 4). There was no recurrence after 3 years of followup.

Discussion

Most reports of nasopharyngeal cysts of branchial origin have been either one- or two-patient studies. Fifteen of the 22 cases involved males. Patients' ages ranged from 2 to 69 years; the most common age range was 52 to 59 years, accounting for eight of the 22 cases.

Sites of origin. In the 22 previously reported cases, 12 involved only the right side of the nasopharynx. Four patients had a cyst only on the left side, four had bilateral disease, one had a cyst at the midline, and one was unreported.

All cysts but one were located in relation with the upper part of the posterior pillar of the tonsil. In light of this finding, it is presumed that these cysts usually arise from the second branchial arch, and they are classified as type IV cysts according to Proctor's classification (table 2). [15]

Nasopharyngeal cysts of branchial origin can develop at any point along an imaginary line drawn from the upper pole of the tonsil and behind the eustachian tube orifice (the so-called lower-level cysts) and along Rosenmuller's s fossa and medially and slightly forward of the midline of the nasopharyngeal vault (upper-level cysts).

Because the cyst in our patient was attached to the lateral nasopharyngeal wall and extended from the middle of the tonsil to the roof of the nasopharynx, it was classified as a lower-level lesion.

Histopathology. In 12 of the 22 previously reported cases, the mucous membrane was lined with either stratifield/pseudostratified ciliated columnar epithelium or ciliated columnar epithelium. In three patients, the lining mucous membrane was either columnar or stratified columnar epithelium. Four patients had a stratified squamous epithelium. In one patient, the cyst was lined with squamous and transitional epithelia and contained lymphoid follicles in the subepithelial plane. There was no mention of histology in the reports of the remaining two patients. In all, seven of these cysts featured subepithelial lymphoid aggregation.

The precise embryologic pathogenesis of pharyngeal cysts of branchial origin is not well understood. The difference in epithelial linings (respiratory or squamous) and the presence of lymphoid tissue in the subepithelial plane make it difficult to determine whether these cysts are endo- or ectodermal. Several theories have been proposed. According to the branchial apparatus theory, type IV cysts arise from a remnant of an internal pharyngeal duct, which would indicate that they are endodermal. [16] On the other hand, seven cysts reported in the literature in addition to the one in our patient featured lymphoid follicles in the cyst wall, while in four other patients the cyst was lined with stratified squamous epithelium; these elements suggest an ectodermal origin.

Wild et al postulated that these cysts are derived from ectopic epithelial cells in the regional lymph nodes and are therefore ectodermal. [17]

Treatment. Different treatment modalities have been used. Of the 22 patients, 18 underwent surgical excision. Two patients underwent aspiration only, and two others were treated with aspiration plus injection of 1 ml of a 5% aqueous solution of ethanolamine oleate as a sclerosing agent. There were no reports of any recurrence.

The transoral surgical approach provides better access to cysts at the lower level, [11,12] whereas the transpalatal approach is better for cysts at the upper level. [13] Tamagawa et al, who performed the endonasal removal, recommend this procedure over the transpalatal approach because it is less invasive and maintains the normal anatomy of the palate. [14]

In our patient, we were able to excise the cyst transorally under direct vision. We believe that this cyst was branchiogenic in origin and that it arose from the second branchial arch at the lower level.

From the Department of Otolaryngology--Head Neck Surgery, Al-Nahda Hospital (Dr. Verma, Dr. Sohail, and Dr. Al-Khabori), and the Department of Pathology, Royal Hospital (Dr. Moosa), Muscat, Sultanate of Oman.

References

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(16.) Maran AG. Benign diseases of the neck. In: Kerr AG, ed. Scott-Brown's Otolaryngology. Vol. 5, 5th ed. London: Butterworths, 1987:287.

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Proctor's classification of crysts arising in the second branchial arch

Type I The cyst lies superficially on the anterior border of the sternocleidomastoid muscle, beneath the cervical fascia

Type II Tye cyst lies beneath the investing layer of the deep cervical fascia and is in contact with the greater vessels

Type III The cyst passes between the internal and external carotid arteries and extends to the pharngeal wall.

Type IV The cyst lies adjacent to the pharyngeal wall and media to the great vessels

Source: Referebce 15.