A patient presents with a sore throat, fever, and fatigue for several days. An advanced practice registered nurse (APRN) notes exudate on the patient's enlarged tonsils. The APRN does a careful lymphatic examination and notes some scattered small, mobile lymph nodes just behind the sternocleidomastoid muscles bilaterally. Which group of nodes is this?

A. Submandibular is incorrect because these lymph nodes are located beneath the mandible along the jawline. They typically drain the tongue, lips, and oral cavity, and are palpated in the submandibular region, not behind the sternocleidomastoid muscle. B. Tonsillar is incorrect because tonsillar (or jugulodigastric) nodes are located just below the angle of the mandible and drain the tonsils and pharynx. While they can be enlarged with tonsillitis, the nodes described in this case are posterior and along the neck, which does not match the tonsillar node location. C. Occipital is incorrect because occipital lymph nodes are located at the base of the skull, posteriorly, and primarily drain the posterior scalp. They are not along the sternocleidomastoid muscles. D. Posterior cervical is correct because posterior cervical lymph nodes are located along the anterior edge of the trapezius muscle and just behind the sternocleidomastoid. These nodes drain the posterior scalp and neck, and may become small, mobile, and tender during upper respiratory infections, such as viral pharyngitis or tonsillitis. Their location along the posterior border of the sternocleidomastoid matches the description in this patient.