Cystic Teratoma of the Parotid Gland Involving Parapharyngeal Space: A Case Report and with Literature Review

Abstract

Background: Teratomas are common neoplasms but are extremely rarely found in the parotid gland region, most benign teratomas are cystic, also known as mature cystic teratomas, and only 9 cases have been reported in the literature.

Case presentation: Herein, we reported a single case of a patient with giant cystic teratoma in the left parotid gland deep lobe extended into the parapharyngeal space. The tumor was diagnosed based on complete preoperative imaging CT and MRI data and then postoperatively confirmed by pathology.

Conclusion: Preoperative CT and MRI scanning are useful in determining the nature of teratomas and perform differential diagnosis of teratoma in the parotid gland by showing calcification, fatty elements, and a fat-liquid level in the parotid gland cyst. Yet, surgery and pathology can provide a final diagnosis.

Background

Teratoma, a tumor derived from germ cells, occurs most often in the tailbone, ovaries, and testicles. The teratoma of the parotid gland is very rare. The first case of teratoma of the parotid gland was reported by Shadid et al in 1975(1). Usually, most teratomas are slow-growing and have clinical features similar to other benign tumors of the parotid gland, so they are often misdiagnosed when in an early stage. Herein, we reported a single case of a patient with giant cystic teratoma in the left parotid gland deep lobe extended into the parapharyngeal space that was diagnosed based on complete preoperative imaging data and then confirmed by pathology postoperatively. In the present study, we presented his clinical and imaging findings. We also performed a brief review of existing domestic and foreign literature, which may improve the accuracy of preoperative diagnosis.

Case Presentation

Our patient was a 36-year-old man of Han nationality who was accidentally diagnosed with a tumor under his left ear three years ago. He did not show any signs of redness, swelling, purulence, pain, or rupture. Ultrasonography at the local hospital suggested a cystic lesion in the parotid gland. A CT examination suggested the possibility of parotid lipoma. At that time, no surgical treatment was performed. Over recent six months, the tumor gradually increased, and the patient suffered from occasional facial discomfort, after which he visited the Head & Neck Oncology Surgery, Affiliated Stomatological Hospital of Medical School, Xi'an Jiaotong University, on September 20, 2019, and was admitted to the hospital for "a tumor in the left parotid gland". Physical examination showed significant distention of the left parotid gland, a nearly-circular tumor with clear boundary, hard texture, and high mobility. His surface skin had a normal color and temperature, without signs of rupture. No enlarged lymph nodes were found in the neck region.

After admission, the patient underwent complete examinations. CT scan of the head and neck showed a tumor 3.0cm x 2.8cm x 2.9cm in size, with a clear boundary and cystic structure, located in the left parotid gland deep lobe, containing contents of different densities, including a large amount of fat and a small amount of soft tissue-like elements (possibly keratinized substances). The medial part extended into the parapharyngeal space and had an eggshell-like calcification in the cyst wall (Figure 1). On MR plain scan and enhanced scan, the tumor had "gourd-like" appearance, and presented as short T1 and long T2 signals mixed up with nodular isoT1 and isoT2 signal and linear short T2 septation. It also had a complete capsule, presented as a low signal in the fat-saturated sequence and accompanied with a fat-liquid level, without significant enhancement (Figures 2a-c). Preoperative imaging diagnosis suggested a benign lesion in the left parotid gland and the possibility of teratoma.

The patient then underwent tumorectomy and facial nerve relaxation (Figure 3). A detail examination of the tumor suggested a cystic tumor located in the parotid gland deep lobe, containing yellow fat-like keratinized substances. Considering that the cyst was too large, some contents inside the cyst were extracted, and the location of the facial nerve trunk was identified at the root of the mastoid process to release, decompress and protect the facial nerve trunk from the pressure from the tumor. As probed, the upper part of the tumor was closely connected to the cartilage of the external acoustic meatus, which was dissected after separation. After this no perforation was observed in the external acoustic meatus. Also, the medial part of the tumor extended into the deep surface of the styloid process and the lateral skull base. The tumor had a thick and tough cystic wall. After the tumor was dissected and fully removed anatomically along the facial nerve trunk, the structure of the facial nerve trunk was not damaged, and the external acoustic meatus was not perforated as inspected. The cyst was sent for postoperative pathological test, which contained light yellow liquid and had a cystic wall of about 0.1mm in thickness.

Under a microscope, the cyst was lined with layered squamous epithelium with superficial keratosis, with sebaceous gland cells, cartilage and fatty tissues in the fibrous cyst wall and a small number of keratinized substances in the cyst lumen. No cellular atypia was detected, and the surrounding parotid tissues were normal. The final diagnosis was mature cystic teratoma in the parotid gland (Figures 4a, b). After surgery, the patient developed mild facial nerve symptom, which was relieved 4 months later. He had no recurrence during the 18-month follow-up visit.

Discussion

Teratoma, a common type of germ cell tumor, most often occurs in the gonads. About 15% of the patients have extragonadal teratoma (e.g., the sacrococcygeal region, retroperitoneum, mediastinum, and pineal region), while this tumor rarely occurs in the head and neck is rare (3% to 5%)(2, 3). Teratoma of the parotid gland is extremely rare and seldom reported. After reviewing relevant literature, only 9 patients with parotid gland teratoma were reported from 1975 to 2019 worldwide (Table 1)(1, 4-11). We failed to access the 2nd and 6th patients' detailed information even though we made substantial effort to do so. Finally, only 8 patients with teratoma of the parotid gland and the relatively complete information (including the one in this report) were analyzed and summarized.

Teratoma most often occurs in females, according to relevant literature(12). About 90% of the head's teratoma occurred in infancy or childhood(13), and a few developed in adulthood. In the older population, teratoma can easily transform into a malignant tumor(14). Among the above-mentioned 8 patients with teratoma in the parotid gland, 6 were females (75.0%), and 2 were males (25.0%), at a ratio of 3:1. Their age ranged from 9 to 36 years, with an average of 22.3 years. The patient in this report was a 36-year-old man, who was the oldest among all patients diagnosed with teratoma in the parotid gland so far. All patients had the teratoma involving unilateral parotid gland, with 4 on the left side (50.0%) and 4 on the right side (50.0%). The patient in this report had the lesion in the deep lobe that extended into the parapharyngeal space, while in other reported cases, the lesions involved the superficial lobe (including 1 case involving a deep lobe). The maximum diameter of the lesion ranged from 1.0 to 3.2cm. All patients visited the hospital for a painless tumor. The course of the disease was between 2 weeks and 4 years, averaging 11 months. Patients had no symptoms (e.g., limitation of mouth opening, hearing impairment, or facial nerve palsy).

Teratoma is a tumor derived from germ cells that can potentially differentiate into somatic cells. According to Batsakis et al(15), most teratomas contain the elements of all ectoderm, mesoderm, and entoderm and can differentiate into skin, nerve, bone, and fatty tissues. In addition, most tumors are cystic (containing liquid, sebum debris, hair, and fatty ingredients) or solid (containing more complex ingredients) and can contain mature, immature, or both mature and immature elements, which distinguishes them from epidermoid cysts and dermoid cysts. Most benign teratomas are cystic, also known as mature cystic teratomas. Ohta et al(9) stated that a teratoma containing skin appendages and cartilage tissues in the cyst wall could be diagnosed as a mature cystic teratoma. Under a microscope, the lesion's cyst wall in this report was lined with layered squamous epithelium, containing sebaceous gland cells, and hyaline cartilage, while fatty tissues were well-differentiated, meeting the diagnostic standards of a mature cystic teratoma.

With reference to clinical physical examination, preoperative diagnostic methods for teratoma in the parotid gland include imaging examinations, such as ultrasonography, CT, and MRI. Ultrasonography is convenient and easy to perform. Under ultrasonography, typical teratoma usually appears as heterogeneous strong light masses and solid-cystic masses containing multiple ingredients and with uneven echo. However, this approach may not be useful for teratoma located deeper within the tissue, which usually requires a CT and MRI scan. Calcification (or ossification) and fatty elements in a teratoma can be visualized on the CT, and a fat-liquid level, hair, tooth, or fat-liquid complex can lead to a definite teratoma diagnosis(16). MRI allows better observation of soft tissues, as well as histopathological changes, such as intratumoral mucus, cartilage matrix, fat, and calcification. It can also be specifically used for fat signaling as fat contains a large number of hydrogen protons and is shown as a high signal in both T1W1 and T2W1, and presented as a low signal due to inhibition of the high signal in the fat-suppressed MRI sequence(17), which increases tissue contrast and reduces artifacts and is of great significance in identifying a teratoma. The combined use of CT and MRI allows qualitative diagnosis and clear observation of the lesion location and scope and its relationship with adjacent tissues. Imaging results of our patient suggested calcification, fat, keratinized substances in the lesion, and the typical fat-liquid levels. Teratoma in the parotid gland with atypical imaging findings can be distinguished from a lipoma, dermoid cyst, epidermoid cyst, branchial cleft cyst, vascular tumor, and pleomorphic adenoma. In this report, the tumor extended to the parapharyngeal space, and the lesion was of a gourd-like shape, which has been detected as two separate lesions on CT and MRI images. Yet, during surgery, it was revealed to be a single lesion that was soft, limited, and surrounded by adjacent structures (the ascending ramus of the mandible, mastoid tip, and peripheral vessels and nerves), thus seeming more like two separate lesions.

The therapy for teratoma in the parotid gland is the same as that used for lipoma and other benign tumors located in the parotid gland, i.e., partial or total lobotomy of the parotid gland by preserving the facial nerve. The part of the parotid gland that needs to be removed is determined according to the tumor's location and size (10, 18). Studies on postoperative complications are rare. Generally, it is believed that such complications result from parotid gland removal and are irrelevant to the nature of the tumor. Postoperative transient facial nerve weakness is the most common complication among patients. Postoperative recurrence of teratoma in the parotid gland is extremely rare. According to existing literature, one patient showed in situ recurrences after surgery(7). Incomplete resection of the tumor may be a possible cause of recurrence, which should be noted in clinical practice. The patient in this report was young, so the superficial lobe in his parotid gland was retained after complete tumor resection, partial parotid gland excision, and anatomical facial nerve relaxation. After surgery, the patient developed a mild facial nerve symptom (he was not able to completely close his left eyelid); this symptom was relieved 4 months later. He had no signs of recurrence of the teratoma during the 15-month follow-up and is still being followed up.

To sum up, teratoma in the parotid gland is rare. A fatty tumor in the parotid gland may suggest the presence of parotid gland teratoma. Preoperative CT and MRI imaging findings may help localize and perform differential diagnosis of teratoma in the parotid gland by showing calcification, fatty elements, and a fat-liquid level in the parotid gland cyst. Yet, the final diagnosis must be confirmed by histopathological examination. For teratoma in the parotid gland, surgical resection is the preferred and effective therapy, in which the facial nerve function should be protected. Patients with teratoma in the parotid gland have a good prognosis but should be regularly followed up.

Declarations

Ethics approval and consent to participate

Not applicable.

Consent for publication

The patient has consented to the submission of the case.

Availability of data and materials

The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.

Competing interests

The authors have no conflicts of interest to disclose.

Funding

None.

Authors' contributions

Hongsheng Liu and Jiafeng Duan carried out the studies, participated in collecting data, and drafted the manuscript. Jia Zhang and Pengfeng Sun performed the data collection and participated in its design. Gang Li participated in Data Interpretation and manuscript revision.  All authors read and approved the final manuscript

Acknowledgements

We are grateful to the patient and her family for allowing the publication of this case report.

References

1. Shadid EA, Engeron O, Glass RT. Benign teratoid tumor of the parotid; Case report. Plastic and reconstructive surgery. 1975;55(3):363-5.
2. Bergé SJ, von Lindern JJ, Appel T, Braumann B, Niederhagen B. Diagnosis and management of cervical teratomas. The British journal of oral & maxillofacial surgery. 2004;42(1):41-5.
3. Stricker TP, Kumar V. Neoplasia. In: Abbas AK, Fausto N, Ster JC, editors. Robbins and Cotran pathologic basis of disease, 8th ed. Philadelphia (PA): Elsevier Saunders. 2010; 295-6.
4. Ayudhya NS, Parichatikanond P, Chinda K. Benign cystic teratoma of the parotid salivary gland: report of the first case in Thailand. Journal of the Medical Association of Thailand = Chotmaihet thangphaet. 1991;74(10):478-80.
5. Pirodda A, Ferri GG, Truzzi M, Cavicchi O. Benign cystic teratoma of the parotid gland. Otolaryngology--head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery. 2001;125(4):429-30.
6. Wang G D, He Y. Teratoma of the parotid gland: a case report. Bengbu Yixueyuan Xuebao. 2003; 28: 470 (in Chinese).
7. Yang D R, Xu H M, Long Q X. Mature cystic teratoma of the parotid gland: a case report. Zhenduan Binglixue Zazhi.2004; 11: 237 (in Chinese).
8. Oudidi A, Alami MN. [Teratoma of the parotid gland: a case report]. Revue de laryngologie - otologie - rhinologie. 2007;128(1-2):125-7.
9. Ohta M, Imamura Y, Mori M, Maegawa H, Kojima A, Fujieda S. Benign cystic teratoma of the parotid gland: a case report. Acta cytologica. 2009;53(4):427-30.
10. Shao L, Guan H, Wan J. Mature cystic teratoma of the parotid gland: a case report and review of the literature. Frontiers of Medicine in China. 2009;3(004):503-6.
11. Yin RJ, Zhao W, XJ S. A case of cystic teratoma in the parotid gland diagnosed by MRI. Journal of Clinical Radiology. 2017;36(3):446.
12. Li H, Zhao T, Wei Q, Yuan H, Cao D, Shen P, et al. Laparoscopic resection of a huge mature cystic teratoma of the right adrenal gland through retroperitoneal approach: a case report and literature review. World journal of surgical oncology. 2015;13:318.
13. Jordan RB, Gauderer MW. Cervical teratomas: an analysis. Literature review and proposed classification. Journal of pediatric surgery. 1988;23(6):583-91.
14. Bonet C, Peñarrocha-Oltra D, Minguez JM, Vera-Sirera B, Peñarrocha-Diago M, Peñarrocha-Diago M. Oral teratomas: a report of 5 cases. Journal of oral and maxillofacial surgery : official journal of the American Association of Oral and Maxillofacial Surgeons. 2012;70(12):2809-13.
15. Batsakis JG. Teratomas of the head and neck. In: Tumors of the head and neck: clinical and pathological considerations. 2nd ed. Baltimore: Williams & Wilkins; 1979; 226-32.
16. Yang DM, Jung DH, Kim H, Kang JH, Kim SH, Kim JH, et al. Retroperitoneal cystic masses: CT, clinical, and pathologic findings and literature review. Radiographics : a review publication of the Radiological Society of North America, Inc. 2004;24(5):1353-65.
17. Chai J, Jin EH. Recent status on MRI chemical shift imaging in quantitative analysis of ectopic fat deposition in vivo. Journal of clinical and experimental medicine, 2013; 12: 2027-30.
18. Tapper D, Lack EE. Teratomas in infancy and childhood. A 54-year experience at the Children's Hospital Medical Center. Annals of surgery. 1983;198(3):398-410.

Table

Table 1. Information of patients with teratoma in the parotid gland in previous reports

NA Not Available