Ανατομική και ιστοπαθολογική μελέτη του καρωτιδικού ελύτρου σε ασθενείς με πιθανές μεταστάσεις Ca της στοματικής κοιλότητας

Abstract

Cancer of the head and neck accounts for approximately 3-4% of all malignant tumors. Over 85-90% of these head and neck cancers are squamous cell carcinomas mainly affecting the oral cavity. Squamous cell carcinomas of oral cavity usually metastasize to the regional lymph nodes, via the lymphatic route. Consequently, effective treatment of these tumors requires the sufficient management of the neck. The surgical management of patients suffering from oral squamous cell carcinomas is the total removal of the lymph-node-bearing tissue on the part of the neck where the metastases have appeared or are expected to occur. This can be accomplished by resection of the primary tumor and neck dissection. During the various types of neck dissections the carotid sheath is removed, especially the part adjacent to the chain of the jugular lymph nodes (from the level of mid-jugular lymph nodes up to the level of the jugulodigastric nodes). It is believed that the jugular chain is better removed if the carotid sheath is also included in the resection specimen. Recurrence in the neck possibly occurs as a result of insufficient excision of the lymph-node-bearing tissue that leaves behind lymphatic tissue and intact lymphatic vessels. One such area may be is the carotid sheath which may be directly involved from large nodal metastases and extensive extracapsular spread. So far, the role of the carotid sheath as a possible bearer of lymphatic vessels and as a potential site of neck recurrence, has not been adequately evaluated in the literature. OBJECTIVE: The purpose of the present study was to investigate the anatomic and histopathologic characteristics of the carotid sheath, which is being removed during the various types of neck dissection, in patients with oral squamous cell carcinomas, in an effort to clarify whether it is essential or redundant to removed the carotid sheath during neck dissection. PATIENTS AND METHODS: During a seven-year period, 50 patients with oral squamous cell carcinomas, underwent 60 neck dissections (modified radical, and supraomohyoid or extended supraomohyoid) in the Department of E-N-L of General Hospital Constantopoulio. The length of the carotid sheath that was resected, extended from below the bifurcation of the carotid artery to the level of the omohyoid muscle (mid-jugular lymph nodes)inferiorly, and up to the level of the posterior belly of the digastric muscle (jugulodigastric lymph nodes) superiorly. The resected specimens were fixed in 10% buffered formalin. The resection in the area of the carotid sheath was performed by blunt dissection and the walls of the carotid artery were completely free of the surrounding connective and fatty tissue. Sixty (60) carotid sheath specimens were obtained for histopathologic evaluation. The microsections were stained with hematoxylin-eosin and examined by a head and neck pathologist under the light microscope (5κm serial sections). The carotid sheath specimens were examined in order to identify possible traces of metastatic disease invading the sheath, as a result of extensive extracapsular spread. The existence of lymphatic vessels and the possible presence of cancer cells within their lumen were also investigated by immunohistochemical methods. Lymphatic vessels were identified using the marker CD 34 (DAKO) for endothelial staining. The possible presence of cancer cells within the lymphatic vessels was assessed using the monoclonal antibody pankeratin (DAKO), which can disclose microscopic metastatic disease. The data from the histopathologic examination were collected and the results were compared with certain parameters from the study protocol, in order to identify any correlation between the extent and stage of malignancy and the histopathologic findings. RESULTS: Light microscopy of the 60 carotid sheath specimens showed that all specimens were composed of fibro-fatty tissue. Scattered neutrophilic infiltration was a common finding. There was no evidence of carotid sheath invasion by tumor cells that could suggest involvement by extracapsular spread. Immunohistochemical evaluation showed an abundance of lymphatic vessels running the course of the carotid sheath. CONCLUSIONS: The conclusions that were drawn from the present study are as follows: 1) The carotid sheath is composed of fibro - fatty tissue, in which a great number of vessels, such as blood vessels (vasa vasorum), as well as lymphatics are found. 2) There was no evidence of carotid sheath invasion by tumor cells that could suggest involvement from extracapsular spread or presence of microscopic metastatic cancer cell emboli in the lumen of the lymphatic vessels. These findings did not correlate with the location of the primary site, the time interval between initial clinical evaluation and time of treatment, the stage of the disease, and the histological differentiation of the tumor. 3) The aforementioned findings seem to indicate that the lymph nodes of the jugular chain communicate with afferent and efferent lymphatic vessels, which travel through the fibro-fatty tissues of the neck and not through the fascia of the carotid sheath. However, further studies are required to support this hypothesis. 4) The maintenance of the carotid sheath during neck dissection of any type, has certain advantages which include: avoidance of unnecessary surgical manipulation of the neurovascular bundle of the neck; reduction in operating time, resulting in less surgical stress for the patient; and finally preservation of a fascial layer over the neurovascular bundle of the neck (particularly over the carotid artery and internal jugular vein). The potential benefit by preserving the carotid sheath is the protection of these anatomic structures from possible rupture, especially in cases of wound breakdown and postoperative radiation therapy. 5) CT and / or MRI evaluation should always complement the clinical assessment of the cervical lymph nodes status. If there is evidence of extracapsular spread, the carotid sheath should be excised together with the jugular chain lymph nodes, because there is an increased possibility for direct carotid sheath tumor invasion. However, the findings of the present study suggest that if no extracapsular spread is identified, the carotid sheath can be preserved during neck dissection with all the advantages that accompany such an action. The decision for carotid sheath preservation can also be justified by the results of frozen sections of highly suspicious for harbouring metastatic disease lymph nodes of the jugular chain, especially when these results are negative for metastasis or extracapsular spread.