A HISTOPATHOLOGICAL ASSESSMENT OF SUBMENTAL (LEVEL IA) LYMPH NODE METASTASIS IN LATERALIZED CANCERS OF THE ORAL CAVITY

Abstract

BACKGROUND Head & neck malignancies contribute to a major proportion of all malignancies in India. At the time of their admission to this facility, up to 80% of these patients present at advanced stages (T3 and T4). Although not very morbid, oral cancers are known to hamper vital day-to-day functions like talking, mastication, swallowing and aesthetics. These cancers tend to be aggressive with an inclination towards rapid infiltration into adjoining tissues and cervical lymphatic spread. Cervical nodal involvement is considered to be a very important prognostic factor in oral squamous cell carcinomas and is known to reduce rates of survival by 50%. Histopathological evaluation of the neck nodes in patients with oral squamous carcinoma is hence very vital as it serves as a strong prognostic indicator. It is therefore mandatory to appropriately manage neck node metastasis, to ensure better locoregional control of disease and enhance the overall survival of the patient. Surgery is the main stay of treatment and is extensive involving composite resection of the tumor, neck dissection, compartment clearance of infratemporal fossa (in T4b tumours) and complex reconstruction. This is followed by adjuvant chemotherapy (CT) or radiotherapy (RT), depending on histopathological features and staging. The first nodal echelon of spread in OSCC is the level I nodes. The first cervical level is further divided into Ia and Ib lymph nodes, also known as submental and submandibular levels, respectively. Out of the two, it has been noted that submandibular group of lymph nodes (Level Ib) are the predominant draining lymph nodes in cancers of most subsites of the oral cavity while level Ia is seen to be involved more commonly in cancers of central compartments (e.g., floor of mouth and tongue). Various studies in the past have shown a very low involvement of submental lymph nodes in cancers of the buccal mucosa/alveolus/gingivobuccal sulcus. This study aims at assessing the level Ia nodal involvement in lateralized oral cancers, there-by enabling us to reconsider the requirement of clearing this level during neck dissection. OBJECTIVES 1. To harvest fibrofatty tissue with lymph nodes from the submental triangle separately in patients undergoing neck dissection for lateralized cancers of the oral cavity 2. To histopathologically assess the involvement of submental (level Ia) lymph nodes for metastasis in the above-mentioned cases METHODS This prospective observation study included 70 patients presenting to the Department of Otorhinolaryngology, R.L Jalappa Hospital, Tamaka, Kolar and diagnosed with lateralized oral cancers and staged T2 to T4, and posted for Elective or Therapeutic neck dissection, from December 2019 till June 2021. Detailed history about history of betel quid or tobacco chewing and onset of the lesion was taken from the patients. Clinical examination of the primary tumour and the oral cavity was done. Routine blood investigations including Contrast enhanced computed tomography (CECT) Skull Base to T4 will be done. Patients were subjected to a biopsy of the primary tumour which was performed under sterile precautions. Patient underwent either therapeutic or elective neck dissection after obtaining formal consent about the procedures and participation in the study. A total of 70 patients were taken as our study population. Fibrofatty tissue along with lymph nodes from the submental triangle will be extracted and assessed histopathologically for nodal metastases. The outcome will be documented and incidence of level Ia nodal metastases in lateralized oral tumours were evaluated. RESULTS: In our study, out of 70 patients, 64 (91.4%) were females and 8.6% were males. Our patients were predominantly between 40-60 years. The most common site of oral squamous cell carcinoma was buccal mucosa in 75.7% followed by 22.8% in alveolus and 1.4% in retromolar trigone (RMT). Ulceroproliferative lesion was the most common type of lesion on presentation seen in 81.9%. Most of our patients were clinically staged T4a (74.1%) and N1 (58.6%). The most common subsite involved was buccal mucosa (75.7%). And majority of our patients were in stage IV (85.7%). Out of the 50 patients who were staged T4a, 32 patients (64%) had skin involvement on clinical examination, and 11 patients (22.0%) had evidence of bony erosion on radiological examination. All patients underwent wide excision of the primary tumour along with neck dissection and subsequent reconstruction. 94.2% of patients underwent modified radical neck dissection (MRND) and 5.7% underwent supraomohyoid neck dissection (SOHND). Most of our patients underwent hemimandibulectomy (87.1%) in view of advanced disease. In our study, 53 (74%) out of 70 patients had cervical lymph node metastasis. Among these 53 patients, 52% had neck N1 status and 45% patients had N2b status on histopathological examination. However, other similar studies have shown majority of their pN+ patients to have pN2 disease. A total of 1634 lymph nodes were evaluated; an average number of 23 lymph nodes was obtained per specimen. A total of 105 (6.4%) nodes were harvested from the submental region. Out of the 1634 nodes, 87 of the total harvested nodes (5.3%) were positive for tumour deposits. Only 5 (5.7%) out of the 87 lymph nodes that showed tumour involvement, belonged to level 1a/submental region. In our study, 3 out of 70 patients (4.2%) with cancer of the lateral subsites of the oral cavity had submental nodes positive for tumour deposits. All 3 patients had skin involvement on clinical examination and 2 out of 3 patients showed radiological features of mandibular erosion on CECT neck. In all 3 cases the cancer was histologically well differentiated. On histopathological evaluation the tumour was noted to have a depth of invasion (DOI) more than 15mm in 2 out of 3 cases. Skin involvement was noted in 2 out 3 patients. CONCLUSION Patients with carcinoma of buccal mucosa, lower alveolus and retromolar trigone had extremely low incidence of metastasis to submental (level Ia) lymph nodes. Those patients in whom submental nodes were found to be positive for tumor deposits, showed features of advanced disease, such as skin involvement and high depth of invasion. This enables us to conclude that level Ia nodes can be spared from clearance during neck dissection in patients with early oral squamous cell carcinomas involving lateral subsites.