Christopher Goh

Regulation of the H19 imprinting gene expression in human nasopharyngeal carcinoma by methylation

In East Asia and Singapore, the human nasopharyngeal carcinoma (NPC) presented clinically is mainly of the undifferentiated type. In contrast, the well‐differentiated squamous NPC is more commonly detected in the West. To study the potential differences in carcinogenesis between undifferentiated and differentiated human NPC, we employed cDNA microarrays to isolate genes that might be specific for human undifferentiated NPC. One of the genes identified to be specifically upregulated in the undifferentiated human NPC cell line CNE‐2 is the human imprinting gene H19. Interestingly, H19 is not expressed in the well‐differentiated human HK1 NPC cells. Northern blot and in situ hybridization analyses also confirmed that the H19 gene is strongly expressed in the undifferentiated CNE‐2 human NPC cell line but not in the well‐differentiated HK1 human NPC cell line. In situ hybridization and reverse transcriptase‐polymerase chain reaction also demonstrated that H19 is specifically expressed in NPC biopsies and not in non‐NPC human tissue biopsies. Furthermore, we demonstrated that deregulation of H19 gene expression in the well‐differentiated human HK1 NPC cells could be induced by the hypomethylation of CpG sites of the H19 promoter region. Hypermethylation of gene promoter regions might therefore be an important epigenetic event that plays a role in the differentiation of human NPC cells and the transcriptional silencing of imprinted genes.

Parotid gland surgery: 4‐Year review of 118 cases in an Asian population

To determine the presentation and management of parotid lesions requiring excision in a largely Chinese Asian population.

Malignant transformation of keratocystic odontogenic tumor: Two case reports

INTRODUCTION Keratocystic odontogenic tumors (KCOTs) are cystic tumours originating from the dental lamina of the maxilla and mandible that are lined with keratinized epithelium. While benign, they can be locally destructive and have a high recurrence rate despite treatment. Rarely, KCOTs may undergo malignant transformation into Primary Intraosseous Squamous Cell Carcinoma (PIOSCC). CASE REPORT This study reports the clinical findings, radiological scans and histopathology of 2 patients with KCOTs that underwent malignant transformation into PIOSCC. DISCUSSION A comprehensive literature review was performed to similar reports documenting the malignant transformation of KCOTs. The potential for KCOTs to undergo malignant change should prompt oral maxillofacial surgeons and otolaryngologists to exercise a high index of suspicion when treating these lesions. Patients persisting with unresolved disease after treatment should be investigated for malignant transformation. Detailed histopathological examination of KCOT specimens is recommended to detect small foci of SCC which may be present in the epithelium.

Phenotypic and functional alterations of Vγ2Vδ2 T cell subsets in patients with active nasopharyngeal carcinoma

IntroductionHuman Vγ2Vδ2 T cells play important role in immunity to infection and cancer by monitoring self and foreign isoprenoid metabolites with their γδ T cell antigen receptors. Like CD4 and CD8 αβ T cells, adult peripheral Vγ2Vδ2 T cells represent a pool of heterogeneous cells with distinct functional capabilities.PurposeThe aim of this study was to characterize the phenotypes and functions of various Vγ2Vδ2 T cell subsets in patients with nasopharyngeal carcinoma (NPC). We sought to develop a better understanding of the role of these cells during the course of disease and to facilitate the development of immunotherapeutic strategies against NPC.ResultsAlthough similar total percentages of peripheral blood Vγ2Vδ2 T cells were found in both NPC patients and normal donors, Vγ2Vδ2 T cells from NPC patients showed decreased cytotoxicity against tumor cells whereas Vγ2Vδ2 T cells from normal donors showed potent cytotoxicity. To investigate further, we compared the phenotypic characteristics of Vγ2Vδ2 T cells from 96 patients with NPC and 54 healthy controls. The fraction of late effector memory Vγ2Vδ2 T cells (TEM RA) was significantly increased in NPC patients with corresponding decreases in the fraction of early memory Vγ2Vδ2 T cells (TCM) compared with those in healthy controls. Moreover, TEM RA and TCM Vγ2Vδ2 cells from NPC patients produced significantly less IFN-γ and TNF-α, potentially contributing to their impaired cytotoxicity. Radiotherapy or concurrent chemo-radiotherapy further increased the TEM RA Vγ2Vδ2 T cell population but did not correct the impaired production of IFN-γ and TNF-α observed for TEM RA Vγ2Vδ2 T cells.ConclusionWe have identified distinct alterations in the Vγ2Vδ2 T cell subsets of patients with NPC. Moreover, the overall cellular effector function of γδ T cells is compromised in these patients. Our data suggest that the contribution of Vγ2Vδ2 T cells to control NPC may depend on the activation state and differentiation of these cells.

Evaluation of recurrent nodal disease after definitive radiation therapy for nasopharyngeal carcinoma: Diagnostic value of fine-needle aspiration cytology and CT scan

Recurrent nodal disease in patients with nasopharyngeal carcinoma (NPC) after definitive radiotherapy presents a difficult clinical problem. This cohort of patients poses a diagnostic challenge to the head and neck surgeon because evaluation of the post‐irradiated neck, both clinically and radiologically, is known to be difficult, and it is not uncommon for neck dissection specimen in suspected recurrent nodal disease to contain no viable tumor cells. Currently, there is no well‐accepted method for the preoperative determination of the presence of malignancy in these nodal diseases.

The suprahyoid neck : normal and pathological anatomy

The suprahyoid neck can be divided into fascia-bound spaces. These spaces, which are readily demonstrated on computed tomography (CT) and magnetic resonance imaging (MRI), form the anatomical framework for generating differential diagnosis and assessing disease extent. By correlating the radiological features with clinical information, the diagnostic possibilities of demonstrated lesions could be narrowed down considerably. Multiple space involvement is common in inflammatory and neoplastic processes and the full extent of these lesions should be outlined to facilitate surgical or radiotherapy planning.

Parotid Gland Surgery for Benign Tumours: Have We Come Full Circle?

Parotid gland surgery has been described for over two centuries. The surgical philosophies in management of parotid gland tumors started off in the 18th century from a conservative approach of simple enucleation so as to minimize post-operative facial nerve palsy rate. This occurred, as there was a lack of understanding of surgical anatomy of the parotid gland and facial nerve. However unacceptably high recurrence rates ensued and this encouraged the further study of parotid gland anatomy till the 1950s when, deriving from a better understanding of the surgical anatomy, superficial parotidectomy with facial nerve identification and preservation became the new standard of care. This method then evolved to a partial superficial parotidectomy as this slightly more conservative approach allowed adequate parotid tumour resection with low recurrence rates and yet minimising post-operative complication such as Freys syndrome. Over the last two decades, a more conservative approach known as an extracapsular dissection of parotid tumour emerged in certain high-volume centers as an alternative to a partial superficial parotidectomy. These centers published better post-operative results with lower postoperative facial nerve palsy rates, less Freys syndrome and faster patient recovery. Dissection of parotid tumours via this technique involves following a plane close to the tumour and is similar to enucleation in terms of its conservative approach with very significant differences post-operatively. This article presents a summary on the surgical philosophies pertaining to parotid gland surgery since its inception two centuries ago.

Obstructive sleep apnoea in a case of thyroglossal duct cyst carcinoma

OBJECTIVES To report a rare case of thyroglossal duct cyst carcinoma which presented with obstructive sleep apnoea, and to highlight the difficulties in making this clinical diagnosis. METHOD Case report and review of the English language literature concerning thyroglossal duct cyst carcinoma. RESULTS Thyroglossal duct cyst carcinoma is a rare clinical entity found in only approximately 1 per cent of all patients operated upon for thyroglossal duct cyst. This condition usually presents in an identical manner to its benign counterpart; atypical presentations have not previously been reported. Our patient is the first reported case of a thyroglossal duct cyst carcinoma first presenting with symptoms of obstructive sleep apnoea, without a neck mass. Complete surgical excision with total thyroidectomy and lymph node clearance was performed, in view of the positive lymph node metastases (seen on imaging) and the need for post-operative radioiodine therapy. CONCLUSION Thyroglossal duct cyst carcinomas may present atypically, posing a diagnostic dilemma for the clinician. For patients diagnosed with obstructive sleep apnoea, it is imperative that a thorough otolaryngological examination be performed to exclude any underlying pathology.

Esthesioneuroblastomas in an Asian population: Similarities and differences *

OBJECTIVE Esthesioneuroblastoma is an uncommon tumor that is described widely among the Caucasians. In Singapore, we see predominantly Asian patients with esthesioneuroblastomas. From our experience, we note significant and interesting differences between our data on Asian patients and the published ones on the Caucasian patients. METHODS A retrospective review of all patients who underwent craniofacial resection for esthesioneuroblastomas was conducted from January 1997 to January 2010. Relevant data were collected and statistical analyses were carried out to determine factors that predicted mortality or complications. RESULTS Out of a total of 48 patients who underwent craniofacial resections, half had esthesioneuroblastomas (50%). There was a peak age distribution at the sixth decade of life and 62% of our patients were male. Both local and regional recurrence rate was 50%. CONCLUSION Majority of our Asian patients who underwent craniofacial resections had esthesioneuroblastomas. There is a male predilection, and we do not see a bimodal age distribution that is commonly reported.

Use of Parotid Pressure Bandage for Drainless Parotidectomies: A Modification of an Old Technique

Objective: The use of fibrin glue has been described in parotidectomies to obviate the need for drains. However, the seroma rate postoperatively can be high. We have modified this technique so as to achieve the same successes without the seroma. Method: A prospective, randomized, case-control study on 54 patients undergoing superficial parotidectomies. All patients had fibrin glue sprayed on the parotid bed intraoperatively. In group A, a pressure bandage was applied over the parotid area for 12 hours postoperatively. In group B, no pressure bandage was used. Results: Group A patients stayed an average of 1.1 days postoperatively while Group B patients stayed 1.6 days. The cost savings in terms of hospitalization was