Gerlach tonsil is

A collection of lymphoid tissue is present in the nasopharynx, behind the tubal opening. It is called the tubal tonsil, also known as Gerlach tonsil. It is continuous with the lateral pa of the pharyngeal tonsil. In Waldeyer's lymphatic ring, the most impoant aggregations are the right and left palatine tonsils. Posteriorly and above there is the pharyngeal tonsil; laterally and above there are the tubal tonsils, and inferiorly there is the lingual tonsil over the posterior pa of the dorsum of the tongue. Ref: BD Chaurasia's HUMAN ANATOMY, Volume 3, 4th edition.