Jon Lester has been undergoing an array of exams in Boston for internal medical issues, including cancer. The tests have prompted serious concern within the organization. Other than citing Lester?s ongoing back problems, Sox general manager Theo Epstein and manager Terry Francona have declined to address any matters concerning the health of one of their brightest prospects. However, on Wednesday Lester was diagnosed with enlarged lymph nodes, according to sources. Such a symptom can be caused by an array of issues, from infections to cancer.