An Atypical Presentation with Diagnostic Challenge of a Large Cell Neuroendocrine Cancer of Lung: A Case Report and Review of the Literature

Large-cell neuroendocrine carcinomas (LCNECs) are relatively rare and aggressive neoplasms of the lung with very poor prognosis. Even though they are included in the classification of nonsmall cell carcinomas, they have a biological behaviour and physiological response to treatment more like small cell carcinomas of lung. We report an atypical case presentation of LCNEC in a 51-year-old gentleman who presented with diffuse metastases to the thoracic and lumbar spine, brain, and liver, posing a diagnostic challenge. The primary small central lung tumor was in close proximity to major vessels, rendering a biopsy of the primary cancer challenging and nearly impossible. The final diagnosis was established through immunohistochemistry staining and examination of liver biopsy from a metastatic lesion. We also included a review of the current literature pertinent to LCNEC, as well as the important role of tumor markers plus immunohistochemistry profiles in determining the origin of unknown primary tumors in such difficult patient presentations. 1. Introduction Large cell neuroendocrine carcinoma is a rare and aggressive neoplasm of lung with a very poor prognosis. It accounts for approximately 1.6–3.1% of all lung cancers [1]. Most LCNECs present as large primary lung masses in the peripheral lung fields; they are more frequently identified on chest radiographs [2]. Patients with LCNEC are less likely to present with pulmonary symptoms such as cough, hemoptysis, or postobstructive pneumonia [3]. Overall, prognosis for the present patient after diagnosis of stage IV LCNEC with distant metastasis was poor, and life expectancy was estimated at around six months. Diagnosis of LCNEC is often a difficult task, which requires histological analysis, cytological evaluation as well as immunohistochemistry. To confirm neuroendocrine origin in the tumor cells, at least one immunohistochemical marker, such as chromogranin, synaptophysin, or CD56, must be positive [4]. Based on the biological presentation and behavior, LCNEC actually has similar prognosis and is treated with similar management regimes as small cell carcinoma [5–7]. We are going to present a case of atypical presentation of LCNEC where the tumor presented with diffuse and distant metastases to liver, spine, brain and including adrenal gland that posed a diagnostic challenge in a 51-year-old gentleman. We also included a small review of the tumor markers that aided in the diagnosis of this tumor. 2. Case Presentation A 51-year-old Caucasian male presented to the emergency department with a two-week history of