Most of maxillary sinus cancer was SCC and adenocarcinoma. SNEC of the sinonasal region is the least common of the sinonasal carcinomas with neuroendocrine differentiation. The SCC or adenocarcinoma in maxillary sinus developed from the lining mucosal epithelium or metaplasia. The histogenesis of the neuroendocrine differentiated tumors is not clear. Whether those cells stem from a common pluripotent precursor or from metaplastic neuroendocrine cells is still unclear. It has been postulated that, outside the lung, this tumor is derived from the neuroendocrine APUD cells, which are widely distributed in the body. The tumors are composed of small-sized regular cells arranged in broad sheets, nests, and cords. Many of the cells contain cribriform nuclei with a fine reticular chromatin pattern and small to moderate amounts of cytoplasm . Immunohistochemical study is essential to make an adequate differential diagnosis from other malignant tumors such as lymphoma, rhabdomyosarcoma, undifferentiated nasopharyngeal carcinoma, and undifferentiated sinonasal carcinoma. SNEC has been reported to stain strongly with synaptophysin and CD56 nerve cell adhesion molecule and weakly with chromogranin A and CAM 5.2/AE-1 .
Yazawa et al. had investigated the clonality of colliding tumor which composed of adenocarcinoma, SCC and large cell neuroendocrine carcinoma . The clonality results were similar in adenomatous and squamous components and different in neuroendocrine component. There were some limitations in that study due to possible DNA fragmentations in formalin fixed tissues. However, it confirmed the adenomatous and squamous components were the same origin and classified it as a colliding tumor of adenosquamous carcinoma (ASC) and neuroendocrine carcinoma. In the literature, ASC is an unusual neoplasm and often misdiagnosed . In our patient, the colliding tumor could originate from a mixture of ASC and the SNEC which gives the tumor a feature of 3 different histologies.
The treatment of SNECs varied considerably over time which includes surgery followed by radiotherapy, concurrent chemo-radiotherapy with or without surgery, and chemotherapy with cisplatin and eoposide followed by radiation or surgery . No consensus yet exists about its treatment. The management of maxillary sinus ASC is also controversial due to its rarity. The prognosis in cases of head and neck SNEC and ASC is very poor because of the high metastatic rate observed. [3, 14] In our patient, the tumor recurred and metastasized rapidly after surgery. Its response to chemotherapy was poor. The diverse components of the tumor could possibly account for its non-responsiveness to chemotherapy and aggressive behaviors.
Recently, EGFR targeting agents such as Cetuximab (C225, Erbitux™), a human-murine chimeric monoclonal antibody, gefitinib and erlotinib were developed. They are less toxic in side effects than cheomotherapies. In locoregionally advanced head and neck SCC, concomitant high-dose radiotherapy plus Cetuximab had been shown to improve locoregional control and reduces mortality . In chemotherapy refractory head and neck cancers, some are responsive to EGFR target treatment. However, from EGFR copy number analysis in each component of the tumor, no EGFR amplification was found. EGFR targeting agents might have limited roles in this rare tumor.