In a large pot over medium heat, combine turkey, broth, tomatoes, green chiles, onion, garlic, and lime juice. Season with cumin, salt, and pepper. Bring to a boil, then reduce heat, and simmer for one hour. Stir in cilantro, and simmer 15 to 20 minutes, until slightly thickened. Spoon into serving bowls, and top with shredded cheese and garnish with avocado or sour cream.