EOD Primary Tumor
**Note 1:** Periosteum is a fibrous membrane that wraps the outer surface of bones. Cortical bone is the dense compact outer layer of the bone. Trabecular, cancellous, or spongy bone (spongiosa) is a porous network of tissue filling the interior of bone, decreasing weight and allowing room for blood vessels and marrow.
**Note 2:** For codes 100-500, the derived EOD T is based on tumor size and depth of invasion. In addition, some of the anatomical structures listed are localized for Summary Stage 2018 while others are regional for Summary Stage 2018. The anatomical structures are divided into two groups: Group 1 is for localized tumors, while Group 2 is for regional tumor.
**Group 1 extension WITH any size tumor: Use the following for codes 100, 150, 200**
Invasive tumor on one side confined to
Tumor crosses midline
Confined to floor of mouth, NOS
**Group 2 extension WITH any size tumor: Use the following for codes 300, 400, 500**
Anterior 2/3 of tongue
Base of tongue
Cortical bone (mandible, NOS)
Periosteum of mandible
Gingiva (alveolar ridge), lower
Lateral pharyngeal wall
Pharyngeal (lingual) surface
Subcutaneous soft tissue of chin/neck
Sublingual gland, including ducts
Submandibular (submaxillary) glands, including ducts
Tonsillar pillars and fossae
**Note 3:** Once the correct group is determined, the codes are then determined based on the depth of invasion.
* Depth of invasion less than or equal to 5 mm or UNKNOWN depth of invasion (codes 100, 300)
* Depth of invasion 5 mm to less than or equal to 10 mm (codes 150, 400)
* Depth of invasion greater than 10 mm (codes 200, 500)
**Note 4:** Involvement through cortical bone is required for assignment of code 600.
* Code 300, 400, or 500 (depending on the depth of invasion) when the tumor is limited to the cortical bone/cortex of the mandible. Invasion of the bone, NOS (mandible, NOS) is **not** equivalent to invasion through the cortical bone (code 600).
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