In Situ Follicular Neoplasia

**Semantic type:** Neoplastic Process

**Definition:** A follicular neoplasia confined to the germinal centers of the lymph nodes, without evidence of disseminated disease. It is characterized by the replacement of a germinal center by neoplastic centrocytes with uniformly intense positivity for BCL2. The surrounding mantle cuff and lymphoid architecture are intact. It has a low rate of progression to follicular lymphoma, but is often associated with prior or synchronous overt lymphoma.

**Synonyms:** - FLIS - Follicular Lymphoma In Situ - ISFN - In Situ Follicular B-Cell Neoplasm - In Situ Follicular Lymphoma