World Journal of Surgical Oncology Unusual Metastasis of Papillary Thyroid Carcinoma to Larynx and Hypopharynx a Case Report

Background: Although direct infiltration of papillary carcinoma of thyroid to larynx, trachea and esophagus is well recognized, lymphatic and vascular metastases to larynx and hypopharynx have rarely been reported.


Introduction
Primary mode of spread in papillary carcinoma thyroid (PCT) is lymphatic [1]. Blood borne metastasis to distant sites is rare. Known sites of distant spread in PCT are bone, lung, skin and brain while involvement of recurrent laryngeal nerve, larynx, pharynx, trachea and esophagus occurs due to direct infiltration [2]. Distant metastases to kidney [3], cerebellum [4], skin [5] and esophagus [6] have also been reported.
Although there are several reports of synchronous association between squamous cell carcinoma of the upper aero digestive tract and lymph node metastasis from occult PCT [7,8], extra nodal metastasis to the larynx and hypopharynx is not reported. We believe this to be the first report of extra nodal metastasis of papillary carcinoma thyroid to larynx and hypopharynx.

Case Report
A 41-year-old man underwent exploration of the neck for fine needle aspiration cytology (FNAC) proven papillary carcinoma thyroid. The attempt at thyroidectomy failed due to extensive extra thyroidal infiltration of the tumor and the patient was referred to cancer centre.
On examination horizontal scar of Kocher's incision was present in front of the neck and fullness was seen over the thyroid bed. Due to postoperative edema, the thyroid could not be assessed.
Bilateral neck nodes were present in levels II, III and IV. Indirect Laryngoscopy (IDL) revealed, mobile vocal cords and multiple mucosal nodules on the posterior pharyngeal wall and the right aryepiglottic fold. The trachea and esophagus were free of disease. A flexible endoscopy of the upper-aero digestive tract confirmed the findings of indirect laryngoscopy and punch biopsies were taken from posterior pharyngeal wall and aryepiglottic fold lesions. Histopathological examination of the biopsy specimen revealed tissue lined by stratified squamous epithelium with metastatic papillary carcinoma in the sub epithelial region (Figure 1). A detailed metastatic workup was carried out which did not reveal metastatic disease elsewhere.
A revision (completion) thyroidectomy and bilateral modified neck dissection, with adjuvant postoperative radioablation of the extra nodal metastasis was planned. Peroperatively he was found to have an 8 × 6 cm firm to hard multinodular lesion in the right lobe and a similar 4 × 3 cm sized lesion in the left lobe of thyroid gland. Multiple lymph nodes were encountered on the right side from level II to V, largest measuring 3 cm. About 4 cm segment of right internal jugular vein was absent. On the left side too, nodes were present from level II to V, with the largest measuring 3 cm. In view of the extensive local regional nodal disease and the high risk of injury to both the recurrent laryngeal nerves an option of laryngopharangectomy with permanent tracheostomy was given but patient did not consent for it, hence, a debulking surgery including excision of the entire right lobe and the isthmus along with right radical neck dissection, left functional neck dissection and central compartment clearance, was carried out. The right recurrent laryngeal nerve (RLN) could not be identified separately during the procedure.
The histopathology of the resected specimen showed papillary carcinoma thyroid (Figure 2) extending to the medial margin of excision. All the lymph nodes in the neck dissection specimen showed metastatic papillary carcinoma. Postoperative scientigraphy carried out after 4 weeks with 100 mc of I 131 administered orally showed 37% neck uptake after 24 hours with a nearly intact left lobe.
In view of the gross residual disease and sub epithelial deposition of the tumor in the posterior pharyngeal wall and right aryepiglottic fold it was decided to subject the patient for postoperative external radiotherapy (RT). The patient however, did not report for any further treatment.

Discussion
Papillary thyroid carcinoma is known for their indolent nature and erratic behavior. Histologically, tall cell [1] and diffuse sclerosis [9] variants of PCT carries a bad prognosis. Other bad prognostic indicators are extra capsular invasion / extra nodal spread, anaplasia of the tumor, age of the patient (>45 yrs) and presence of distant metastasis [1,2]. A direct association between presence of extranodal spread and occurrence of distant metastasis has also been reported [10].
PCT commonly spreads through lymphatics and vascular spread is rare. However, when occurs it is usually to bone, brain, lungs and soft tissue. Involvement of other structures in neck like larynx, trachea and esophagus is mainly due to direct infiltration of tumor into these structures.
Unlike the cases of direct laryngeal invasion [2] by the tumor that presents with symptoms of stridor/dysphagia Biopsy from the right aryepiglottic fold showing intact squa-mous epithelium with underlying papillary carcinoma with papillary and follicular patterns Figure 1 Biopsy from the right aryepiglottic fold showing intact squamous epithelium with underlying papillary carcinoma with papillary and follicular patterns. (H&E × 250) or hoarseness, the present case did not have any symptom and on routine indirect laryngoscopic examination was found to have discrete laryngeal and hypopharyngeal nodules covered with normal squamous epithelium, which were not in continuity with the thyroid tumor. Direct laryngoscopic findings and its subsequent operative and histological confirmation prompt us to reason that these discrete nodules would have been a consequence of a either a retrograde lymphatic [11] or vascular spread. Retrograde or aberrant lymphatic spread to retropharyngeal nodes or the pharynx per se is very unlikely because of the absence of lymphoid component in the laryngeal and pharyngeal specimen and in parapharangeal or retropharangeal spaces, however a retrograde subepithelial spread to larynx and hypopharynx can not be ruled out. Absence of central compartment and retropharyngeal lymphadenopathy and predominant nodal spread to lateral compartment (level II, III, IV) is also an argument against this. A computerized tomogram (CT) or magnetic resonance image (MRI) would have helped in differentiating the direct invasion or metastasis. However due to financial constraints it was not carried out in the present patient. Radioiodine scan is not of help in such situations as in presence of thyroid tissue, majority of the metastasis do not take up radioiodine.
Advanced thyroid malignancies generally presents difficult therapeutic decisions especially when there is extra nodal and extra capsular spread of the tumor. A judicious combination of surgical clearance combined with radio ablation is the key to the management of such tumors [12]. However, when gross residual thyroid tissue is left behind a post operative external beam RT is preferable to radioablation because of the need for a high dose of radioiodine to get optimum results in a disease which is already destined to have a bad outcome [13,14].