EJSO (2004) 30, 80–84
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EDUCATIONAL ARTICLE
Parapharyngeal metastases from thyroid cancer G. Desutera, M. Lonneuxb, I. Plouin-Gaudona, F. Jamarb, E. Cochec, ´goiree, G. Andryf, M. Hamoira,* B. Weynandd, J. Rahierd, V. Gre a
Department of Otolaryngology—Head and Neck Surgery, Head and Neck Oncology Program, ´ Catholique de Louvain (UCL), St Luc University Hospital, Brussels, Belgium Universite b Department of Nuclear Medicine, Head and Neck Oncology Program, ´ Catholique de Louvain (UCL), St Luc University Hospital, Brussels, Belgium Universite c ´ Catholique de Louvain (UCL), Department of Radiology, Head and Neck Oncology Program, Universite St Luc University Hospital, Brussels, Belgium d ´ Catholique de Louvain (UCL), Department of Pathology, Head and Neck Oncology Program, Universite St Luc University Hospital, Brussels, Belgium e Department of Radiation Oncology, Head and Neck Oncology Program, ´ Catholique de Louvain (UCL), St Luc University Hospital, Brussels, Belgium Universite f ´ Libre de Bruxelles (ULB), Department of Head and Neck Surgery, Jules Bordet Institute, Universite Brussels, Belgium Accepted for publication 17 October 2003
KEYWORDS Thyroid carcinoma; Parapharyngeal tumour; Neck metastases
Summary Aim. To emphasise the pattern of lymphatic dissemination in the parapharyngeal space from thyroid cancer. Patients and method. Among 696 patients treated for thyroid cancer between 1986 and 2001, parapharyngeal metastasis was diagnosed in three patients, previously treated for papillary thyroid carcinoma. Results. All three patients have been treated by surgical resection through lateral cervical approach. Two of them were controlled regionally whereas the remaining one had a submucosal pharyngeal metastasis locally resected 27 months after parapharyngeal resection. Conclusions. Parapharyngeal metastasis is rare, but should be a recognized pattern of lymphatic dissemination from thyroid carcinoma to avoid unnecessary radioiodine and because surgical resection is efficacious with acceptable morbidity. Q 2003 Elsevier Ltd. All rights reserved.
Introduction Lymph node dissemination of papillary thyroid carcinoma (PTC) is often reported to the central compartment of the neck followed by the lateral *Corresponding author. Tel.: þ32-2-764-19-76; fax: þ 32-2764-89-35. E-mail address:
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regions.1 By contrast, lymph node metastasis in the parapharyngeal region is rarely mentioned. The parapharyngeal space is anatomically subdivided into two regions. The anterior, prestyloid region tends to be the space for the development of salivary gland tumours whereas the posterior, post styloid region will more often give rise to tumours derived from vascular or neurogenic structures.2,3
0748-7983/$ - see front matter Q 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.ejso.2003.10.004
Parapharyngeal metastases from thyroid cancer
Thyroid lymphatic drainage The thyroid lymphatic drainage is complex. According to Rouvie `re, it comprises four main groups of collection channels: (1) the inferomedial route draining the pre and paratracheal lymph nodes; it is the main route for metastases, (2) the superomedial route which terminates in the lymph node situated at the level of the cricothyroid membrane also called Delphian lymph node, (3) the superolateral route extending up to the superior node of the internal jugular chain, (4) the inferolateral route draining the nodes of the supraclavicular and jugulosubclavian chains.4 The thyroid lymphatic network is hence rich in anastomoses between the numerous lymphatic channels. This explains the multiple patterns of lymph node metastases from PTC. Rouvie `re has described a lymphatic vessel connecting the upper pole of the thyroid gland to the retropharyngeal lymphatic system. This lymphatic trunk was reported in only 20% of the cases.4 Behind the fascia of the superior constrictor muscle is an anatomical dehiscence allowing the parapharyngeal spaces and retropharyngeal spaces to communicate freely with each other, explaining the dissemination to the parapharyngeal compartment through the retropharyngeal compartment.5 We here report a small series of parapharyngeal metastases from thyroid carcinoma and sum up the position on this unusual pattern of metastatic dissemination from thyroid cancer.
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consecutive patients have been operated for thyroid cancer at St Luc University Hospital, Brussels. All patients had had histologic confirmation of thyroid cancer. PTC was diagnosed in 555 cases. In three patients, parapharyngeal metastasis of PTC was secondarily diagnosed 1, 2.5 and 3 years after initial treatment, respectively.
Results All three patients had undergone total thyroidectomy and bilateral neck dissection for lymph node metastases in the neck. Diagnosis of parapharyngeal metastasis was established by an oropharyngeal examination, including nasofibroscopy, in two patients and by computerised tomography (CT) in the remaining one. In the two first patients, CT and magnetic resonance imaging (MRI) (Figs. 1 and 2) or 18-fluorodeoxyglucose positron emission tomography (FDG-Pet scan)—CT coregistration (Fig. 3) confirmed diagnosis. All were first treated by radioiodine without resolution and underwent successful surgery through lateral cervical approach without mandibulotomy or temporary tracheotomy. Postoperative morbidity was minimal without definitive cranial nerve paralysis. Within a follow-up ranged from 22 to 52 months, all patients were alive. Two of them were controlled regionally. The third one had a submucosal pharyngeal metastasis transorally resected 27 months after parapharyngeal resection
Patients and findings Between January 1986 and December 2001, 696
Figure 1 Contrast-enhanced CT (axial view) showing a well-defined right parapharyngeal tumour.
Figure 2 MRI (coronal view) showing right parapharyngeal tumour with displacement of the rhinopharyngeal mucosa
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Figure 3 (a) CT, (b) ‘Inverse grey’ axial Pet scan, and (c) ‘hot iron’ Pet scan-CT coregistration images of right parapharyngeal metastasis.
and remained free of disease, 5 months following this last intervention.
Discussion Parapharyngeal space tumours represent only 0.5% of all head and neck tumours. Only 20% of these are malignant.2,6 Some 50% of the neoplasms arise from the deep lobe of the parotid gland or minor salivary gland. These lesions are typically benign pleomorphic adenoma and involve the pre styloid compartment of the parapharyngeal space. In the retrostyloid compartment, the most common tumours are neurogenic (schwannoma, paraganglioma, neurofibroma). Other benign and malignant tumours may arise in the parapharyngeal space, including meningioma and lymphoma. Squamous cell carcinoma of the upper aerodigestive tract such as the rhinopharynx, oropharynx, hypopharynx and oral cavity may metastasize to the lymph nodes of the parapharyngeal space.3,6 Thyroid carcinoma may present in two ways: primitive parapharyngeal lymph node metastasis from an occult thyroid carcinoma; and secondary parapharyngeal mass, as a neck recurrence of a previously treated thyroid carcinoma. Literature review from last three decades, using MedlineR data base has identified 30 cases of parapharyngeal thyroid carcinoma metastases.5,7 – 24 Most of the reported cases (24/30) were metastases from PTC.
size (1 – 6 cm) and the patients were generally asymptomatic when the tumour did not exceed 3 cm in size. A lymph node metastatic from an occult thyroid carcinoma was found in 8/28 cases. The diagnosis of a parapharyngeal metastasis during the follow-up of previously treated patients was made in 20/28 cases. Metastatic laterocervical lymph nodes were reported in 9/20 cases. When pointed out, the primary tumour was in the upper pole of the thyroid gland in all cases. The latency of clinical discovery is variable. Leger et al. reported parapharyngeal metastases in four patients previously treated by total thyroidectomy and neck dissection. In three of them, the diagnosis was asserted during 131I scan, 4 weeks after surgery, suggesting a probable presence before initial surgical treatment.23 Other authors reported recurrence in the parapharyngeal space, many years following initial treatment.19,20,22
Treatment Among 28 patients, 17 were operated through transoral (3), transmandibular (4), laterocervical (7) or other (3) approach without major complications. Four patients were treated by radioiodine only, two patients had external radiotherapy and 3 patients had a combination of 131I and external radiotherapy. Long-term follow-up was generally not reported.
Initial work-up of thyroid carcinoma Clinical features of parapharyngeal metastases Reported symptoms were poorly specific: headaches, temporomandibular disorder related pain, snoring and dysphagia. Metastases were variable in
Although it is costly and burdensome to propose CT or MRI for any suspect thyroid nodule, it may be useful in suspicion of thyroid carcinoma with palpable lymph nodes. Besides the confirmation of lymph node metastases, the parapharyngeal space
Parapharyngeal metastases from thyroid cancer
may be accurately assessed. Ultrasonography is able to assess the lateral neck,25 but does not explore the parapharyngeal region.
Follow-up of thyroid carcinoma During follow-up of patients treated for differentiated thyroid carcinoma, the development of cervical lymph node and an elevation of serum thyroglobulin (Tg) should suspect recurrence. The presence of detectable Tg concentration, even if influenced by the TSH concentration, the anti-Tg antibodies and the dosage technique, is still a good predictive factor for the presence of thyroid tissue. However, an undetectable Tg concentration does not exclude definitively metastases.26 Tg may be undetectable in up to 20% of patients presenting with neck metastases.1 We believe that the presence of an unexplained elevation of Tg concentration and the occurrence of clinically invaded lymph nodes in the neck, should be an indication for an examination of the oropharynx including nasofibroscopy and CT or MRI of the neck including the parapharyngeal spaces. FDG-Pet scan is considered as the most recent efficient tool to detect lymph node recurrences,27 but is poorly efficient in localizing with accuracy the pictured abnormalities. Coregistration with CT or MRI seems to be the optimal solution.
Conclusions Parapharyngeal lymph node metastasis is a rare pattern of invasion of thyroid cancer but it should not be overlooked and then should be included in the differential diagnosis of parapharyngeal masses. During the follow-up of patients treated for differentiated thyroid carcinoma, the presence of an unexplained raised Tg concentration and the presence metastatic lymph nodes in the neck, should lead to examination of the oropharynx by nasofibroscopy and CT or MRI of the neck including the parapharyngeal spaces. Surgical resection is the only effective treatment.
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