2027 ICD-10-CM Diagnosis Code C84.42Peripheral T-cell lymphoma, not elsewhere classified, intrathoracic lymph nodes
ICD-10-CM Codes›C00–D49›C81-C96›C84
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Risk Adjusts — HCC 19
- Chronic Condition
C84.42 is a billable ICD-10-CM diagnosis code for peripheral T-cell lymphoma, not elsewhere classified, intrathoracic lymph nodes. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 820 through 825, 840 through 842, 974 through 976. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 68 closely related codes. Coders also document this condition as peripheral T-cell lymphoma of thoracic lymph node. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Non-Hodgkin lymphoma.
For Medicare Advantage risk adjustment, C84.42 maps to CMS-HCC Category 19 (Myelodysplastic Syndromes, Multiple Myeloma, and Other Cancers) under the V28 model, adding a risk factor of about 1.798 for a community, non-dual, aged beneficiary in payment year 2027.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
C84.42 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2027.
Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Peripheral T-cell lymphoma of thoracic lymph node
- T-cell lymphoma of lymph nodes of thorax
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to C84.42: its own notes plus those printed at C84, block C81-C96, and Chapter 2. A note printed at a category, block or chapter applies to every code under it.
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
Notes
General instructions on how these codes are used.
- 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).
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name C84.42, its category, or a range that includes it.
Excludes1 6
These codes carry an Excludes1 note naming C84.42: they are not reported together with it, unless the two conditions are unrelated.
- C82 Follicular lymphomamature T/NK-cell lymphomas (C84.-) names C84.-, which includes this code
- C83.0 Small cell B-cell lymphomamature T/NK-cell lymphomas (C84.-) names C84.-, which includes this code
- C83.3 Diffuse large B-cell lymphomamature T/NK-cell lymphomas (C84.-) names C84.-, which includes this code
- C84.0 Mycosis fungoidesperipheral T-cell lymphoma, not elsewhere classified (C84.4-) names C84.4-, which includes this code
- C84.9 Mature T/NK-cell lymphomas, unspecifiedmature T-cell lymphoma, not elsewhere classified (C84.4-) names C84.4-, which includes this code
- C86 Other specified types of T/NK-cell lymphomamature T/NK-cell lymphomas (C84.-) names C84.-, which includes this code
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Lymphoma, T-Cell, Peripheral
a group of malignant lymphomas thought to derive from peripheral t-lymphocytes in lymph nodes and other nonlymphoid sites. they include a broad spectrum of lymphocyte morphology, but in all instances express t-cell markers admixed with epithelioid histiocytes, plasma cells, and eosinophils. although markedly similar to large-cell immunoblastic lymphoma (lymphoma, large-cell, immunoblastic), this group's unique features warrant separate treatment.
Patient EducationClinical
Lymphoma
Lymphoma is a cancer of a part of the immune system called the lymph system. There are many types of lymphoma. One type is Hodgkin disease. The rest are called non-Hodgkin lymphomas.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert C84.42 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About C84.42Overview
Is C84.42 (Peripheral T-cell lymphoma, not elsewhere classified) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report peripheral T-cell lymphoma, not elsewhere classified, intrathoracic lymph nodes on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does C84.42 group to?
When peripheral T-cell lymphoma, not elsewhere classified, intrathoracic lymph nodes is the principal diagnosis on an inpatient stay, it groups to MS-DRG 820, 821, 822, 823, 824, 825, 840, 841, 842, 974, 975, 976, with relative weights from 0.7879 to 6.2454 depending on complications. Higher weights mean higher Medicare reimbursement.
Is C84.42 a CC or MCC?
CMS lists C84.42 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 68 closely related codes in its exclusion list.
Can C84.42 be reported with Z85.72?
Not as a rule. The Excludes1 note at C84, which applies to C84.42, lists "personal history of non-Hodgkin lymphoma (Z85.72)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).
What is the ICD-9 equivalent of C84.42?
Under the General Equivalence Mappings, peripheral T-cell lymphoma, not elsewhere classified, intrathoracic lymph nodes converts to ICD-9-CM 202.72 (periph T cell lym thorax). The mapping is approximate, so confirm the match fits the documentation.
What HCC is C84.42?
C84.42 (peripheral T-cell lymphoma, not elsewhere classified, intrathoracic lymph nodes) maps to CMS-HCC Category 19 (Myelodysplastic Syndromes, Multiple Myeloma, and Other Cancers), commonly written as HCC 19, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 10 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 21.
Does C84.42 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, C84.42 adds a risk adjustment factor of about 1.798 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.957 to 1.989 depending on the payment segment). A more severe related category (HCC 17 and HCC 18) supersedes it when both are reported. See the full factor table on the HCC 19 category page.
