SNOMED CT Editorial Guide

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Hematologic, lymphatic

There is more than one meaning of hematologic. A definition based on hematological system structure includes hematopoietic and lymphoid structures (including bone marrow, spleen, thymus, lymph nodes, etc), as well as the cellular components of blood. Hematologic neoplasms clearly fit this definition.

A definition based on clinical usage by hematologists is broader. Disorders of hemostasis and thrombosis are often managed by hematologists, but these do not have a common structural overlap with the lymphoid and hematopoietic systems (with the exception of platelets and megakaryocytes). For clarity, hematologic disorder is a navigational concept that is used to define a reference set that includes disorders of blood and blood forming organs, as well as disorders of hemostasis and thrombosis, depending on what is intended.

Hematologic disorders, lymphoid and myeloid neoplasms

Hematologic disorders may refer to disorders of: hematopoietic cell origin; blood forming organs (bone marrow, lymph nodes, spleen, thymus, and other lymph tissues); cellular components of blood; or function of hemostatic and thrombotic systems.

Diseases of the blood forming organs (bone marrow, lymph nodes, etc.) can be defined by any one or a combination of the following:

The morphology (neoplastic diseases, at a minimum, include those morphologies covered by neoplasms in the International Classification of Diseases for Oncology, ICD-O).

For example,

For example,

For some disorders, like T-cell lymphomas, and plasma cell and immunosecretory disorders, it is important to distinguish those defined by morphology, site, or manifestation.

T-cell lymphomas can be subcategorized according to the primary site, a lymph node, the skin, or other extranodal site. This means that a site of lymphoid structure cannot be the defining characteristic of the parent concept T-cell lymphoma. Its defining attribute should be morphology alone.

Plasma cell and immunosecretory disorders (e.g. monoclonal gammopathy, heavy chain disease, Waldenstrom's macroglobulinemia) are defined by their manifestations, i.e. the type of monoclonal protein they secrete. Others (e.g. myeloma, plasmacytoma) are defined by their morphology, regardless of whether or not they are secretory.

Immunosecretory disorders may have a morphology of plasma cell neoplasm, even though no mass has been identified and the monoclonal protein may be the only evidence that there is a clonal neoplasm.

In general, lymphoid and myeloid neoplasms can be modeled with their morphologies, but without a site. Leukemias and myelodysplastic syndromes are modeled with Finding Site, bone marrow structure (body structure). 

Coagulation, hemostasis, thrombosis

There is more than one meaning of coagulation. A broad meaning, to stop bleeding, is better described as hemostasis. A more narrow definition, limited to the formation of the fibrin clot, might exclude certain components of hemostasis (e.g the ability to stop hemorrhage through the actions of blood vessels, collagen, endothelial cells, and platelets, in the absence of clotting). Individuals with congenital fibrinogen deficiency cannot form fibrin clots, yet their bodies are able to stop bleeding. Therefore, coagulation disorders are kinds of hemostatic disorders.

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