Which of the following is NOT one of the accessory lymph organs?

The spleen is classified as a vital lymphatic organ, playing a critical role in filtering blood, storing blood cells, and facilitating immune responses. Accessory lymph organs, on the other hand, are structures that assist in the body's immune response but are not essential for the lymphatic system's primary functions.

The tonsils, adenoids, and Peyer’s patches are all considered accessory lymph organs. The tonsils act as the first line of defense against pathogens that enter through the oral cavity, while the adenoids serve a similar purpose in the nasopharynx. Peyer's patches, which are aggregates of lymphoid tissue found in the small intestine, contribute to immune responses against gut pathogens.

Thus, the spleen's primary role as a lymphatic organ differentiates it from the accessory lymph organs, making it the correct response in this context.