#### § 81.23 Guidelines for cancers for which primary site is unknown.

(a) In claims for which the primary cancer site cannot be determined, but a site of metastasis is known, DOL will calculate probability of causation estimates for various likely primary sites. Table 1 of this paragraph (a) indicates the primary cancer site(s) DOL will use in NIOSH-IREP when the primary cancer site is unknown.

Table 1 to Paragraph (a)

Primary cancers (ICD-10-CM codes) for which probability of causation is to be calculated, if only a secondary cancer site is known. “M” indicates cancer site should be used for males only, and “F” indicates the cancer site should be used for females only.

| Secondary cancer
(ICD-10-CM code) | ICD-10-CM code of likely primary cancers |
| --- | --- |
| Lymph nodes of head, face and neck (C77.0) | C01, C02, C07(M), C08(M), C09(M), C10(M), C14(F), C32(M), C33, C34, C43, C44, C50(F), C73(F), D03. |
| Intrathoracic lymph nodes (C77.1) | C15(M), C33, C34, C50(F). |
| Intra-abdominal lymph nodes (C77.2) | C15(M), C16(M), C18, C25(F), C33, C34, C50(F), C53(F), C61(M), C64, C65, C66, C68, C82(F), C84(F) (excluding C84.6, C84.7), C85(F), C86(F) (excluding C86.5, C86.6), C91.4(F), C96(F). |
| Lymph nodes of axilla and upper limb (C77.3) | C33, C34, C43, C50(F) , D03. |
| Inguinal and lower limb lymph nodes (C77.4) | C19(M), C20(M), C21(M), C33, C34, C43, C44(F), C60(M), C63(M), D03. |
| Intrapelvic lymph nodes (C77.5) | C18(M), C19(F), C20(F), C21(F), C33(M), C34(M), C53(F), C54(F), C61(M), C67. |
| Lymph nodes of multiple sites (C77.8) | C15(M), C16(M), C18(M), C33, C34, C50(F). |
| Lymph nodes, site unspecified (C77.9) | C15(M), C16, C18, C33, C34, C43, C50(F), C61(M), D03. |
| Lung (C78.0) | C18, C33, C34, C43(M), C50(F), C61(M), C67(M), C64, C65, C66, C68, D03(M). |
| Mediastinum (C78.1) | C15(M), C33, C34, C50(F). |
| Pleura (C78.2) | C15(M), C18(M), C33, C34, C50(F), C56(F), C57(F), C61(M), C64(M), C65(M), C66(M), C68(M). |
| Other respiratory organs (C78.3) | C15, C18(M), C32, C33, C34, C44(M), C50(F), C61(M), C73(F). |
| Small intestine, including duodenum (C78.4) | C17, C18, C25, C33, C34, C49, C43(M), C50(F), C56(F), C57(F), C64(M), C65(M), C66(M), C68(M), D03(M). |
| Large intestine and rectum (C78.5) | C18, C19, C20, C21, C33, C34, C50(F), C56(F), C57(F), C61(M). |
| Retroperitoneum and peritoneum (C78.6) | C16, C18, C19(M), C20(M), C21(M), C25, C33(M), C34(M), C49, C50(F), C54(F), C56(F), C57(F). |
| Liver, specified as secondary (C78.7) | C16(M), C18, C19(M), C20(M), C21(M), C25, C33, C34, C50(F). |
| Other digestive organs (C78.8) | C15(M), C16, C18, C25, C33, C34, C50(F), C61(M). |
| Kidney (C79.0) | C18, C33, C34, C50(F), C53(F), C61(M), C67, C64, C65, C66, C68, C82(F), C84(F) (excluding C84.6, C84.7), C85(F), C86(F) (excluding C86.5, C86.6), C91.4(F), C96(F). |
| Other urinary organs (C79.1) | C18, C50(F), C53(F), C56(F), C57(F), C61(M), C67, C64(F), C65(F), C66(F), C68(F). |
| Skin (C79.2) | C18, C33, C34, C49(M), C43, C44(M), C50(F), C64(M), C65(M), C66(M), C68(M), D03. |
| Brain and spinal cord (C79.3) | C33, C34, C43(M), C50(F), D03(M). |
| Other parts of nervous system (C79.4) | C33, C34, C43(M), C50(F), C61(M), C82, C84 (excluding C84.6, C84.7), C85, C86 (excluding C86.5, C86.6), C91.4, C96, D03(M). |
| Bone and bone marrow (C79.5) | C33, C34, C50(F), C61(M). |
| Ovary (C79.6) | C18(F), C50(F), C56(F), C57(F). |
| Adrenal gland (C79.7) | C18(F), C33, C34, C50(F). |
| Other specified sites (C79.8) | C18, C33, C34, C43(M), C50(F), C56(F), C57(F), C61(M), C67(M), D03(M). |
| Unspecified sites (C79.9) | C18, C33, C34, C43(M), C50(F), C56(F), C57(F), C61(M), C67(M), D03(M). |
| Carcinoid tumor of distant lymph nodes (C7B.01) | C15(M), C16, C18, C33, C34, C43, C50(F),C61(M), D03. |
| Carcinoid tumor of liver (C7B.02) | C16(M), C18, C19(M), C20(M), C21(M), C25, C33, C34, C50(F). |
| Carcinoid tumor of bone (C7B.03) | C33, C34, C50(F), C61(M). |
| Carcinoid tumor of peritoneum (C7B.04) | C16, C18, C19(M), C20(M), C21(M), C25, C33(M), C34(M), C49, C50(F), C54(F), C56(F), C57(F). |
| Merkel cell carcinoma (C7B.1) | C18, C33, C34, C49(M), C43, C44(M), C50(F), C64(M), C65(M), C66(M), C68(M), D03. |

(b) DOL will select the site producing the highest estimate for probability of causation to adjudicate the claim.

[67 FR 22309, May 2, 2002, as amended at 84 FR 37590, Aug. 1, 2019]