Colliding tumor of the paranasal sinus

Sinonasal malignant neoplasms comprise only 3% of all head and neck malignancies. Synchronous and metachronous tumors of the head and neck have been described, but rarely have there been reports of a single tumor with two distinct histologies. Here, we describe a case of a sinonasal malignant neoplasm with two distinct histologies. A case report and literature review was performed. We present a case of paranasal sinus neoplasm involving two malignant cell types. An 83-year-old woman presented with a 2-year history of symptoms suggestive of chronic sinusitis, which included nasal congestion and intermittent midface pressure. More recently, her symptoms progressed with the development of left-side epistaxis and she was found to have a mass in the left maxillary and ethmoid regions. A biopsy of the maxillary sinus mass revealed a moderately differentiated squamous cell carcinoma (SCC). She underwent complete resection of the lesion through an extended endoscopic approach. Final pathological analysis showed a malignant neoplasm with two distinct malignant morphologies; a moderately differentiated SCC and small cell neuroendocrine carcinoma. Appropriate diagnosis and treatment of head and neck malignancy depends on accurate tumor classification and staging. We present a case of a sinonasal tumor with two distinct malignant entities and review the available literature on the subject. Additionally, we discuss the etiologic theories and challenges in planning the optimal approach to management in this scenario.