CS Extension

Notes

**Note 1**: The cortex of a bone is the dense outer shell that provides strength to the bone; the spongy center of a bone is the cancellous portion. The periosteum of the bone is the fibrous membrane covering of a bone that contains the blood vessels and nerves; the periosteum is similar to the capsule on a visceral organ. **Note 2**: The assignment of T1and T2 categories for tumors of bone is based on tumor size. A physician's statement of the T category may be used to code CS Tumor Size and/or CS Extension if this is the only information in the medical record regarding one or both of these fields. However the two fields are coded independently: for example the record may document size but not extension, other than the physician's statement of the T category. Use codes 310 and 350 as appropriate to code CS Extension based on a statement of T when no other extension information is available. **Note 3**: The term "skip metastasis" is not used with a consistent meaning in the literature. In some cases, it refers to discontinuous metastasis in the same bone as the primary tumor, while in other cases it refers to discontinuous metastasis in an adjacent bone, usually in the same limb. For AJCC staging, discontinuous metastasis in the same bone is classified as T3 (coded in CS Extension), and discontinuous metastasis in an adjacent bone is classified as M1b (coded in CS Mets at DX). If a primary bone tumor is stated as having "skip metastasis" or "skip lesions" with no other information regarding the bone involved, use code 820 in CS Extension.

Code	Description	AJCC 7 T	AJCC 6 T	Summary Stage 1977 T	Summary Stage 2000 T
100	Invasive tumor confined to cortex of bone	Extension Size	Extension Size	L	L
200	Extension beyond cortex to periosteum (No break in periosteum)	Extension Size	Extension Size	L	L
300	Localized, NOS	Extension Size	Extension Size	L	L
310	Stated as T1 with no other information on extension	Extension Size	Extension Size	L	L
350	Stated as T2 with no other information on extension	Extension Size	Extension Size	L	L
400	Extension beyond periosteum to surrounding tissues, including adjacent skeletal muscle(s)	Extension Size	Extension Size	RE	RE
600	Adjacent bone/cartilage	Extension Size	Extension Size	RE	RE
700	Skin	Extension Size	Extension Size	D	D
800	Further contiguous extension	Extension Size	Extension Size	D	D
820	Discontinuous tumors in the primary bone site	T3	T3	D	D
850	Stated as T3 with no other information on extension	T3	T3	D	D
950	No evidence of primary tumor	T0	T0	U	U
999	Unknown; extension not stated Primary tumor cannot be assessed Not documented in patient record	TX	TX	U	U

- For CS Extension codes 100-800 ONLY, the T category for AJCC 7 staging is assigned based on the value of CS Tumor Size, as shown in the Extension Size Table for this schema. - For CS Extension codes 100-800 ONLY, the T category for AJCC 6 staging is assigned based on the value of CS Tumor Size, as shown in the Extension Size Table for this schema.