NN.2 Basic Concepts and Definitions
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## NN.2 Basic Concepts and Definitions

### NN.2.1 Specimen

A physical object (or a collection of objects) is a specimen when the laboratory considers it a single discrete, uniquely identified unit that is the subject of one or more steps in the laboratory (diagnostic) workflow.

To say the same thing in a slightly different way: "Specimen" is defined as a role played by a physical entity (one or more physical objects considered as single unit) when the entity is identified uniquely by the laboratory and is the direct subject of more steps in a laboratory (diagnostic) workflow.

It is worthwhile to expand on this very basic, high level definition because it contains implications that are important to the development and implementation of the DICOM Specimen Module. In particular:

1. A single discrete physical object or a collection of several physical objects can act as a single specimen as long as the collection is considered a unit during the laboratory (diagnostic) process step involved. In other words, a specimen may include multiple physical pieces, as long as they are considered a single unit in the workflow. For example, when multiple fragments of tissue are placed in a cassette, most laboratories would consider that collection of fragments as one specimen (one "block").

2. A specimen must be identified . It must have an ID that identifies it as a unique subject in the laboratory workflow. An entity that does not have an identifier is not a specimen.

3. Specimens are sampled and processed during a laboratory's (diagnostic) workflow. Sampling can create new (child) specimens. These child specimens are full specimens in their own right (they have unique identifiers and are direct subjects in one or more steps in the laboratory's (diagnostic) workflow. This property of specimens (that can be created from existing specimens by sampling) extends a common definition of specimen, which limits the word to the original object received for examination (e.g., from surgery).

4. However, child specimens can and do carry some attributes from ancestors . For example, a tissue section cut from a formalin fixed block remains formalin fixed, and a tissue section cut from a block dissected from the proximal margin of a colon resection is still made up of tissue from the proximal margin. A description of a specimen therefore, may require description of its parent specimens.

5. A specimen is defined by decisions in the laboratory workflow. For example, in a typical laboratory, multiple tissue sections cut from a single block and placed on the same slide are considered a single specimen (as single unit identified by the slide number). However, if the histotechnologists had placed each tissue section on its own slide (and given each slide a unique number), each tissue section would be a specimen in its own right .

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