A 57-year old man has been a smoker for 40 years. He has los…

A 57-year old man has been a smoker for 40 years. He has lost 12 pounds during the past 6 months and this has been accompanied by a chronic cough and general fatigue. He reports no fever, nausea, or vomiting, but he had a recent episode of hemoptysis (presence of blood in sputum). A chest X-ray and bronchoscopy reveal a 5 cm diameter mass in the right bronchus. Histologic examination of tissue biopsied from the mass reveals epithelial cells with a high nuclear:cytoplasmic ratio and deposition of  extracellular keratin pearls. Which of the following findings is most likely to be present in this man?