Extranodal

Extranodal refers to sites outside the lymph nodes. In medicine, the term describes disease processes that originate in tissues or organs not part of the lymphatic system. Extranodal involvement is especially relevant in lymphoid malignancies, where tumor cells may arise in non-nodal tissue and can affect multiple organ systems, sometimes without obvious nodal disease.

Extranodal lymphomas are lymphoid cancers that originate outside lymph nodes. They may present as primary extranodal disease or as secondary involvement from nodal lymphoma. Common extranodal sites include the gastrointestinal tract (most notably gastric MALT lymphoma), skin, brain and spinal cord, eyes and orbit, upper airways, testis, and lungs. Some subtypes, such as extranodal NK/T-cell lymphoma, nasal type, show a predilection for the upper aerodigestive tract. The pattern of extranodal involvement influences symptoms and prognosis.

Diagnosis relies on tissue biopsy from the affected extranodal site, supported by imaging, laboratory studies, and immunophenotyping. Staging systems for lymphomas incorporate extranodal involvement; detection of distant extranodal disease generally corresponds to higher stage and can guide treatment choices, including systemic therapy and targeted approaches. In other medical contexts, extranodal describes infections or metastases that occur outside lymph nodes, underscoring that clinically significant pathology is not limited to nodal tissue.