ABSTRACT Paraneoplastic syndrome refers to the signs and symptoms that manifest themselves distantly from the primary site or metastatic site of a tumour

ABSTRACT
Paraneoplastic syndrome refers to the signs and symptoms that manifest themselves distantly from the primary site or metastatic site of a tumour. It represents a group of disorder that result due to the systemic effects rather than the local effect of the tumour. Several cases of nasopharyngeal carcinoma have been reported to present with these remote effects. The underlying mechanisms that give rise to these indirect manifestations have been attributed to humoral factors or immune response. Cross reactivity between normal tissues and host antitumour antibody also plays a critical role. Paraneoplastic Syndrome has been broadly classified into six main groups: Dermatologic or cutaneous, endocrine, hematologic, osteoarticular/rheumatologic, neurological an ocular. Dermatologic manifestations represent the most common paraneoplastic effect of NPC. These indirect effects usually antedate the diagnosis of NPC in about 80 % of cases whereas in some other they may also occur after the cancer is diagnosed. Although these phenomena are relatively rarely associated with NPC compared to other cancers such as lung cancers where they occur more frequently, the possibility of a nasopharyngeal carcinoma should also be considered by clinicians. This may provide an opportunity to detect cancer at an earlier stage or even help to detect occult malignancy. In most cases the sign and symptoms resolve following treatment of the underlying cancer while in certain cases directed therapy may be required. Reappearance of paraneoplasia usually occurs with case recurrences. Thereby their presence following remission may also help to identify relapses at an early stage. This contribution provides an overview of the paraneoplastic manifestations of NPC which is one the most frequently encountered malignancy in mainland China with emphasis on those which are more commonly associated with NPC.

INTRODUCTION
Paraneoplastic syndrome occurs in up to 10% cancer cases. The most common cancers associated with these phenomena are: lung (SCLC, NSCLC), pancreatic, lymphoma (Hodgkin and non-Hodgkin), prostate, ovary. However, till date several cases of paraneoplasia have been reported in association with nasopharyngeal carcinoma. NPC accounts for about 18% of malignancy in China. In contrast to America and other regions where the cancer occur rarely, NPC is responsible for a huge burden of disease in China. Despite recent advances, many challenges are yet to be overcome in this aspect of oncology. As such a thorough understanding of the presentations of NPC is of utmost value for the timely diagnosis of the malignancy. Clinicians are very well acquainted with the typical signs and symptoms of NPC which include cervical lymphadenopathy in 75% of cases, nasal obstruction, epistaxis, recurrent otitis media, sore throat, hearing loss, facial numbness due to cranial nerve dysfunctions (mainly II-VI, IX-XII). However, when it comes to the paraneoplastic manifestations, they are often underdiagnosed. Therefore, the aim of this review is to provide a proper understanding of the current status on the paraneoplastic effects of NPC for the timely detection of cases and improving outcome and survival of patients.

CLASSIFICATION OF PARANEOPLASTIC SYNDROME ASSOCIATED WITH NPC

In 1940, cancers were first reported to present with distant signs and symptoms which were not due to local mass effects. These effects were then termed as paraneoplastic syndrome which is also known as non-metastatic effects, remote effects, indirect effects, distant effects. They were proposed to result due to secretion of peptides from the tumour. These substances may mimic normal hormones, interfere with normal metabolic pathway or trigger an immune response. In some cases, the cause maybe idiopathic. They may affect different organ and tissues and has been therefore divided into six main groups according to the organ or system they influence.