extramedular

Extramedullary is a medical term meaning located outside the bone marrow or, more broadly, outside the medullary tissue of an organ. The standard spelling in modern usage is extramedullary; extramedular appears in some older texts or as a variant but is less common.

In hematology, extramedullary hematopoiesis (EMH) refers to the production of blood cells outside the bone marrow. EMH commonly occurs in the liver and spleen but can involve other tissues. It often arises as a compensatory response to severe or chronic marrow failure, such as certain anemias or myelofibrosis. Clinically, EMH can cause organomegaly, mass effects, or symptoms related to compression. Diagnosis relies on imaging (ultrasound, CT, MRI) and, when needed, tissue biopsy. Management focuses on treating the underlying condition; in symptomatic cases, therapies may include transfusions, radiotherapy to shrinking masses, or, rarely, surgical debulking.

Extramedullary refers to tumors or neoplasms arising outside the bone marrow. Extramedullary plasmacytoma is a solitary plasma cell tumor that occurs outside bone and is most often located in the head and neck region. It requires staging to exclude systemic multiple myeloma; treatment typically involves radiotherapy, with surgery in selected cases. Other extramedullary neoplasms include metastases that have spread to sites outside the marrow or soft tissues, and various extramedullary tumors of the spine and central nervous system.

In summary, extramedullary designates tissue or processes occurring outside the marrow cavity, most commonly described in the contexts of hematopoiesis and neoplasia. See also intramedullary and spinal extramedullary lesions for related concepts.