Hi, I've a doubt for which I've no answer.

The fourth field of the TCGA barcode contains the information about the sample, either primary tumor, metastatic, etc

For instance `TCGA-93-A4JP-01A-11H-A24S-13`, this is a primary tumor, but what does the A next to the 02 means? Sometimes I've sen other letter than A such C, E...


Thanks
**Edit April 6th, 2020:**

Since I posted this answer, this page seems to have come online: <a href="https://docs.gdc.cancer.gov/Encyclopedia/pages/TCGA_Barcode/">TCGA Barcode</a>

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# TCGA Barcode
<a href="https://imgbb.com/"><img src="https://image.ibb.co/bSkaW7/barcode.png" alt="barcode" border="0"></a>

<a href="https://ibb.co/neTUr7"><img src="https://preview.ibb.co/g8g4PS/TCGA_barcode.jpg" alt="TCGA_barcode" border="0"></a>


# Code tables

Go here for the code tables for further in depth details:

 - https://gdc.cancer.gov/resources-tcga-users/tcga-code-tables

Kevin
