2021 ICD-10-CM Diagnosis Code C73

Malignant neoplasm of thyroid gland

    2016 2017 2018 2019 2020 2021 Billable/Specific Code
  • C73 is a billable/specific ICD-10-CM code that can be used to indicate a diagnosis for reimbursement purposes.
  • The 2021 edition of ICD-10-CM C73 became effective on October 1, 2020.
  • This is the American ICD-10-CM version of C73 - other international versions of ICD-10 C73 may differ.
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Certain conditions have both an underlying etiology and multiple body system manifestations due to the underlying etiology. For such conditions the ICD-10-CM has a coding convention that requires the underlying condition be sequenced first followed by the manifestation. Wherever such a combination exists there is a "use additional code" note at the etiology code, and a "code first" note at the manifestation code. These instructional notes indicate the proper sequencing order of the codes, etiology followed by manifestation. In most cases the manifestation codes will have in the code title, "in diseases classified elsewhere." Codes with this title are a component of the etiology/manifestation convention. The code title indicates that it is a manifestation code. "In diseases classified elsewhere" codes are never permitted to be used as first listed or principle diagnosis codes. They must be used in conjunction with an underlying condition code and they must be listed following the underlying condition.
  • code to identify any functional activity
The following code(s) above C73 contain annotation back-references
Annotation Back-References
In this context, annotation back-references refer to codes that contain:
  • Applicable To annotations, or
  • Code Also annotations, or
  • Code First annotations, or
  • Excludes1 annotations, or
  • Excludes2 annotations, or
  • Includes annotations, or
  • Note annotations, or
  • Use Additional annotations
that may be applicable to C73:
  • C00-D49
    2021 ICD-10-CM Range C00-D49


    • Functional activity
    • All neoplasms are classified in this chapter, whether they are functionally active or not. An additional code from Chapter 4 may be used, to identify functional activity associated with any neoplasm.
    • Morphology [Histology]
    • Chapter 2 classifies neoplasms primarily by site (topography), with broad groupings for behavior, malignant, in situ, benign, etc. The Table of Neoplasms should be used to identify the correct topography code. In a few cases, such as for malignant melanoma and certain neuroendocrine tumors, the morphology (histologic type) is included in the category and codes.
    • Primary malignant neoplasms overlapping site boundaries
    • A primary malignant neoplasm that overlaps two or more contiguous (next to each other) sites should be classified to the subcategory/code .8 ('overlapping lesion'), unless the combination is specifically indexed elsewhere. For multiple neoplasms of the same site that are not contiguous, such as tumors in different quadrants of the same breast, codes for each site should be assigned.
    • Malignant neoplasm of ectopic tissue
    • Malignant neoplasms of ectopic tissue are to be coded to the site mentioned, e.g., ectopic pancreatic malignant neoplasms are coded to pancreas, unspecified (C25.9).
Approximate Synonyms
  • Anaplastic thyroid carcinoma
  • Cancer from the thyroid metastatic to lymph nodes of neck
  • Cancer metastatic to lymph node from thyroid
  • Cancer of the thyroglossal duct
  • Cancer of the thyroid
  • Cancer of the thyroid, anaplastic
  • Cancer of the thyroid, follicular
  • Cancer of the thyroid, hurthle cell
  • Cancer of the thyroid, medullary
  • Cancer of the thyroid, metastatic to bone
  • Cancer of the thyroid, papillary
  • Cancer of the thyroid, with metastasis to bilateral lungs
  • Cancer of the thyroid, with metastasis to left lung
  • Cancer of the thyroid, with metastasis to lungs
  • Cancer of the thyroid, with metastasis to right lung
  • Follicular thyroid carcinoma
  • Hurthle cell carcinoma of thyroid
  • Malignant tumor of thyroid gland
  • Medullary thyroid carcinoma
  • Papillary thyroid carcinoma
  • Primary malignant neoplasm of thyroglossal duct
  • Secondary malignant neoplasm of bilateral lungs from thyroid
  • Secondary malignant neoplasm of left lung from thyroid
  • Secondary malignant neoplasm of lungs from thyroid
  • Secondary malignant neoplasm of lymph nodes from thyroid
  • Secondary malignant neoplasm of lymph nodes of neck from thyroid
  • Secondary malignant neoplasm of right lung from thyroid
  • Thyroid cancer metastatic to bone
  • Thyroid cancer metastatic to unspecified site
Clinical Information
  • A primary or metastatic malignant neoplasm affecting the thyroid gland.
ICD-10-CM C73 is grouped within Diagnostic Related Group(s) (MS-DRG v38.0):
  • 011 Tracheostomy for face, mouth and neck diagnoses or laryngectomy with mcc
  • 012 Tracheostomy for face, mouth and neck diagnoses or laryngectomy with cc
  • 013 Tracheostomy for face, mouth and neck diagnoses or laryngectomy without cc/mcc
  • 643 Endocrine disorders with mcc
  • 644 Endocrine disorders with cc
  • 645 Endocrine disorders without cc/mcc

Convert C73 to ICD-9-CM

Code History
  • 2016 (effective 10/1/2015): New code (first year of non-draft ICD-10-CM)
  • 2017 (effective 10/1/2016): No change
  • 2018 (effective 10/1/2017): No change
  • 2019 (effective 10/1/2018): No change
  • 2020 (effective 10/1/2019): No change
  • 2021 (effective 10/1/2020): No change
Code annotations containing back-references to C73:
  • Type 1 Excludes: C75
    ICD-10-CM Diagnosis Code C75

    Malignant neoplasm of other endocrine glands and related structures

      2016 2017 2018 2019 2020 2021 Non-Billable/Non-Specific Code
    Type 1 Excludes
    • malignant carcinoid tumors (C7A.0-)
    • malignant neoplasm of adrenal gland (C74.-)
    • malignant neoplasm of endocrine pancreas (C25.4)
    • malignant neoplasm of islets of Langerhans (C25.4)
    • malignant neoplasm of ovary (C56.-)
    • malignant neoplasm of testis (C62.-)
    • malignant neoplasm of thymus (C37)
    • malignant neoplasm of thyroid gland (C73)
    • malignant neuroendocrine tumors (C7A.-)

Diagnosis Index entries containing back-references to C73:

ICD-10-CM Codes Adjacent To C73
C72.31 Malignant neoplasm of right optic nerve
C72.32 Malignant neoplasm of left optic nerve
C72.4 Malignant neoplasm of acoustic nerve
C72.40 Malignant neoplasm of unspecified acoustic nerve
C72.41 Malignant neoplasm of right acoustic nerve
C72.42 Malignant neoplasm of left acoustic nerve
C72.5 Malignant neoplasm of other and unspecified cranial nerves
C72.50 Malignant neoplasm of unspecified cranial nerve
C72.59 Malignant neoplasm of other cranial nerves
C72.9 Malignant neoplasm of central nervous system, unspecified
C73 Malignant neoplasm of thyroid gland
C74 Malignant neoplasm of adrenal gland
C74.0 Malignant neoplasm of cortex of adrenal gland
C74.00 Malignant neoplasm of cortex of unspecified adrenal gland
C74.01 Malignant neoplasm of cortex of right adrenal gland
C74.02 Malignant neoplasm of cortex of left adrenal gland
C74.1 Malignant neoplasm of medulla of adrenal gland
C74.10 Malignant neoplasm of medulla of unspecified adrenal gland
C74.11 Malignant neoplasm of medulla of right adrenal gland
C74.12 Malignant neoplasm of medulla of left adrenal gland
C74.9 Malignant neoplasm of unspecified part of adrenal gland

Reimbursement claims with a date of service on or after October 1, 2015 require the use of ICD-10-CM codes.