<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 70-year-old man is brought to the emergency department by his wife because of progressive confusion for the past 2 weeks. He has also had a 4.5-kg 10-lb weight loss and fatigue during the last 6 months. Physical examination shows enlarged lymph nodes in the right axilla and faint expiratory wheezing in the right middle lung field. He is only oriented to person. Serum studies show a sodium concentration of 125 mEqL and increased antidiuretic hormone concentration. An x-ray of the chest shows a right-sided hilar mass with mediastinal fullness. A biopsy of the hilar mass is most likely to show cells that stain positive for which of the following?? A: Desmin, B: Neurofilament, C: Napsin A, D: S-100, E: Neuron-specific enolase,  <response>: This is a clinical vignette describing a 70-year-old man with confusion, weight loss, fatigue, lymphadenopathy, wheezing, hyponatremia, and a right hilar lung mass. The question asks which immunohistochemical stain the biopsy of the hilar mass is most likely to be positive for. Based on the clinical presentation, the most likely diagnosis is small cell lung cancer. Small cell lung cancer often presents with paraneoplastic syndromes such as SIADH causing hyponatremia. It also frequently metastasizes to lymph nodes and causes local effects like wheezing from compression of airways. Small cell lung cancer stains positive for neuron-specific enolase on immunohistochemistry. The other answer choices are markers for other types of tissues not consistent with small cell lung cancer.E: Neuron-specific enolase 