Over the past 30 years, there has been a sharp rise in the incidence of thyroid cancer, with papillary carcinoma accounting for more than 90% of cases [1]. In contrast to follicular carcinoma, papillary thyroid carcinoma typically spreads by lymphatics; vascular spread is uncommon. Common locations of distant metastases include the skin, brain, lungs, and trachea. Direct infiltration causes involvement of the recurrent laryngeal nerve and the esophagus, larynx, and pharynx [2,3]. There have been reports of distant metastases to the lung, kidney, cerebellum, skin, and esophagus [2,4-7].

Though they appear to be uncommon, hematopoietic and distant metastases most frequently localize to the bone, lungs, skin, and brain. Direct infiltration results in involvement of the pharynx, oesophagus, trachea, and recurrent laryngeal nerve [8,9].

Because of their near anatomical localization, metastatic disease to the hypopharynx and parapharyngeal area appears to be simple; yet, a few cases of parapharyngeal [10,11] and hypopharyngeal [12,13] involvement have been reported in the literature. We report a case of parapharyngeal space and hypopharynx metastases from papillary thyroid cancer.

A 71-year-old man referred to our department for 5 months of chronic dysphonia. The patient had undergone a total thyroidectomy ten years previously and the histological diagnosis was papillary thyroid carcinoma. A sub-mucosal tumor in the left lateral pharyngeal wall that expanded toward the midline was discovered via indirect laryngoscopy. The left vocal cord was paralyzed, and the larynx was twisted to the right. An airway narrowing mass of 2.2x3.7 cm was found in the neck's axial magnetic resonance imaging segment, located in the lateral wall of the hypopharynx. The mass was lined from the level of tracheal cartilage to the parapharyngeal area, according to a sagittal MRI of the neck. The results of the indirect laryngoscopy were validated by a flexible endoscopy of the upper aerodigestive tract, and punch biopsies were obtained from lesions in the left postero lateral pharyngeal wall. A histopathological analysis of the biopsy sample showed that the subepithelial region of the tissue was bordered by stratified squamous epithelium with metastatic papillary carcinoma (Figure 1). After a thorough metastatic workup, no more metastatic disease was found.

The tumor was dissected upward, passing through the retropharyngeal space, the parapharyngeal space, the base of the skull, and the left sinus pyriformis and great horn of the thyroid cartilage. The entire 8 cm long tumor was removed. The procedure was associated lymph node dissection, with permanent tracheostomy was given. Primary sutures were used to correct the hypopharyngeal defect. Under the epithelium was a papillary structure, as shown by a histological examination. A papillary carcinoma metastasis was the diagnosis. The patient gave their informed permission.

Figure 1: Biopsy of the tumor process of the left posterolateral wall of the hypopharynx showing intact squamous epithelium with underlying papillary-type carcinoma.

The most prevalent thyroid gland cancer, papillary carcinoma, has a good overall survival rate and peaks in the middle decades of life. Even with the excellent survival rates, metastasis causes poor outcomes for a tiny subset of patients. The lymphatic system is typically the route of spread; arterial spread is uncommon but typically results in metastases to the lungs, brain, bone, and soft tissues. Direct tumor infiltration is a common way for other neck tissues to become involved.

The current case had a chronic dysphonia and, upon indirect laryngoscopic examination, it was discovered that the tumoral process was in the left posterolateral wall of the hypopharynx with extension to the parapharyngeal region, not in continuity with the thyroid tumor. Based on the direct laryngoscopic observations and the subsequent confirmation by surgery and histology, we may conclude that the tumoral process was likely the result of either a vascular or retrograde lymphatic [14] spread. Due to the lack of a lymphoid component in the laryngeal and pharyngeal samples as well as in parapharangeal or retropharangeal lymphatic spread, retrograde or aberrant lymphatic spread to retropharyngeal nodes or the pharynx per se is extremely rare.

Radiological imaging techniques are required because parapharyngeal masses can be challenging to evaluate clinically, particularly in patients who have had a prior neck dissection. While ultrasonography is a valuable diagnostic tool for neck lymphadenopathies and thyroid disorders, it is not useful in the parapharyngeal region [18]. While MRIs are better for soft tissue imaging than CTs, CTs can still be quite affordable.

The literature frequently reports thyroid metastases to the parapharyngeal area [8,11,12]. There have been reports of one case of combined laryngeal and hypopharynx metastasis [12] and one case of ocular metastasis [18]. In this case, we present a patient who had undergone a total thyroidectomy with papillary thyroid carcinoma diagnosis and presented a hypopharyngeal and parapharyngeal metastasis 10 years after the neck dissection.

Generally, tumors malignes de la thyroide at an advanced stage provide therapeutic challenges, especially when the tumor spreads outside the capsule and ganglions. The key to managing these tumors is a carefully considered combination of surgical ablation and radiofrequency ablation [15]. However, if residual thyroid tissue is left in place, external postoperative radiotherapy is preferable to radioablation due to the high dose of radioiode required to achieve optimal results in a disease that is already destined to have a bad outcome [16,17].

Because of this case's exceptional rarity and to emphasize the value of a multimodal approach in the treatment of such extranodal disorders, it is being reported. A drastic strategy for treating the current illness would involve a partial laryngo-pharyngectomy and a whole thyroidectomy. If more than half of the pharynx had been removed, repair with a myocutaneous flap would have been necessary. However, the inherent morbidity and the alternative of debulking surgery and adjuvant postoperative radiotherapy/radioablation make this unpalatable to the surgeon most of the time [15].

Finally, it should be noted that there are very few reports of lymphatic and vascular metastases of papillary thyroid cancer to the hypopharynx and parapharyngeal area separately. It is quite uncommon for both hypopharyngeal and parapharyngeal space involvement to be present as it was in our instance.

Seldom have reports of papillary thyroid cancer lymphatic and vascular metastases to the hypopharynx and parapharyngeal area been made. It is quite uncommon for both hypopharyngeal and parapharyngeal space involvement to be present as it was in our instance.

1. Matin MA, Islam MS, Razzak MA, Khanam M, Kabir S, Saifuddin AKM, et al. Incidence of thyroid cancer in thyroid swelling, study of 200 cases. Bangladesh J Otorhinolaryngol. 2021; 27:12-6.
2. Varghese BT, Mathews A, Pandey M, Pradeep VM. Unusual metastasis of papillary thyroid carcinoma to larynx and hypopharynx a case report. World J Surg Oncol. 2003; 1:7.
3. Mcaffrey TV, Bergstralh EJ, Hay ID. Locally invasive papillary thyroid carcinoma. Head Neck. 1994; 16:165-172.
4. Graham LD, Roe SM. Metastatic papillary thyroid carcinoma presenting as a primary renal neoplasm. Am Surg. 1995; 61: 732-734.
5. Pacak K, Sweeney DC, Wartofsky L, Mark AS, Punja U, Azzam CJ, et al. Solitary cerebellar metastasis from papillary thyroid carcinoma: A case report. Thyroid. 1998; 8: 327-335.
6. Lissak B, Vannetzel JM, Gallouedec N, Berrod JL, Rieu M. Solitary skin metastasis as the presenting feature of differentiated thyroid microcarcinoma: Report of two cases. J Endocrinol Invest. 1995; 18: 813-816.
7. Cooney BS, Levine MS, Schnall MD. Metastatic thyroid carcinoma presenting as an expansible intraluminal esophageal mass. Abdom Imaging. 1995; 20: 20-22.
8. Cooney BS, Levine MS, Schnall MD. Metastatic thyroid carcinoma presenting as an expansile intraluminal esophageal mass. Abdom Imaging. 1995; 20: 20-22.
9. Ferrario F, Roselli R, Machhi A. Occult thyroid carcinoma presenting as a parapharyngeal mass. J Laryngol Otol. 1995; 109:1204-1206.
10. Pearlman SJ, Lawson W, Biller HF. Occult medullary carcinoma of the thyroid presenting as neck and parapharyngeal metastases. Otolaryngol Head Neck Surg. 1988; 99: 509-512.
11. Varghese B, Mathews A, Pandey M, Pradeep VM. Unusual metastasis of papillary thyroid carcinoma to larynx and hypopharynx a case report. World J Surg Oncol. 2003; 1:7.
12. Hakeem AH, Pradhan SA, Bhele S, Tubachi J. Metastasis of papillary thyroid cancer to the larynx and pharynx: unusual case report. Eur Arch Otorhinolaryngol. 2012; 269: 2585-2587.
13. Tobias MJ. Anatomy of the Human Lymphatic System: A compendium translated from the original Anatomie des Lymphatiques de l Homme by H. Rouviere rearranged for the use of students and practitioners. Ann Arbor, Edward Bros. 1938.
14. Mazzaferri EL. Thyroid remnant I131 ablation for papillary and follicular thyroid carcinoma. Thyroid. 1997; 7: 265-271.
15. ODoherty MJ, Nunan TO, Croft DN. Radionucleotide and therapy of thyroid cancer. Nucl Med Commun. 1993; 14: 736-755.
16. Harmer CL. Radiotherapy in the management of thyroid cancer. Ann Acad Med Singapore. 1996; 25: 413-419.
17. Filho FDR, Lima GG, Ferreria FVA, Lima MG, Hissa MN. Orbital metastasis as primary clinical manisfestation of thyroid carcinoma-case report and literature review. Arq Bras Endocrinol Metabol. 2008; 52: 1497-1500.
18. Wang XL, Xu ZG, Wu YH, Liu SY, Yu Y. Surgical management of parapharyngeal lymph node metastasis of thryoid carcinoma: a retrospective study of 25 patients. Chin Med J (Engl). 2012; 125: 3635-3639.