A Rare Case of Sinonasal Large Cell Neuroendocrine Carcinoma with Lymph Node Metastasis

Abstract Introduction/Objective Sinonasal carcinomas comprise less than 1% of cancers, and the most common types are squamous cell carcinoma at 51.6% and adenocarcinoma at 12.6%. There are only limited published reports of sinonasal large-cell neuroendocrine carcinoma (LCNEC). This entity has distinguishing immunohistochemical and histomorphologic features; it stains positively for neuroendocrine markers (i.e., synaptophysin and CD56) and histologically has abundant amphophilic cytoplasm with prominent nucleoli. Methods/Case Report We present a 60-year-old female patient who was evaluated for a submandibular neck lump. Computed tomography identified a 3.2 x 1.8 x 1.6 cm enhancing lesion with central necrosis in the right submandibular space, representing either an enlarged necrotic right submandibular lymph node or a neoplasm arising from the right submandibular gland. The pathology of the lymph node biopsy was consistent with metastatic high- grade neuroendocrine carcinoma. The neoplastic cells stained positively for INSM1, CK8/18, CK AE1/3 (subset), TTF- 1, and Ki-67 (50%). Dotatate positron emission tomography showed evidence of focal activity in the right anterior nasal cavity supporting evidence with primary nasal cavity origin. Nasal endoscopy was performed, visualizing an area of necrotic friable tissue. Pathology confirmed the presence of large cell neuroendocrine carcinoma in the right nasal biopsies with metastatic LCNEC in right neck levels 1, 2A, 2B, 3, and 4. The malignant cells on hematoxylin and eosin stain had similar morphology to those in the initial lymph node biopsy, supporting a diagnosis of LCNEC. Results (if a Case Study enter NA) NA Conclusion Sinonasal large-cell neuroendocrine carcinomas are extremely rare. Upon literature search, there have been fewer than ten case reports published of this entity. Furthermore, large-cell neuroendocrine carcinoma behaves aggressively, and diagnosing this entity could result in earlier intervention and better patient outcomes. Highlighting the possibility of this diagnosis could broaden differentials in neoplasms that arise from the nose.