Question 1

What is ICD-10 code D38.3?

Accepted Answer

D38.3 is the ICD-10-CM diagnosis code for neoplasm of uncertain behavior of mediastinum. A growth in the mediastinum (the space in the chest between the lungs) that cannot yet be determined to be cancer or benign. These tumors may require additional imaging or biopsy. D38.3 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering neoplasms of uncertain behavior, polycythemia vera and myelodysplastic syndromes (d37-d48).

D38.3 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.

Mediastinal masses have a broad differential diagnosis; ensure pathology confirms uncertain behavior rather than a specific diagnosis.

Question 2

Is D38.3 an HCC code?

Accepted Answer

No. D38.3 is a billable ICD-10-CM code but does not map to any payment HCC category under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can still be reported on Medicare Advantage encounter data submissions, but it does not contribute to the beneficiary's Risk Adjustment Factor (RAF) score and therefore does not affect the risk-adjusted capitation payment to the plan. V28 reached 100% phase-in for payment year 2026.

Question 3

Is D38.3 billable?

Accepted Answer

Yes. D38.3 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. D38.3 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

Question 4

What is the V28 vs V24 difference for D38.3?

Accepted Answer

D38.3 does not map to a payment HCC under either the CMS-HCC V28 risk adjustment model or the older V24 model. V28 reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition. Because neither community model rewards D38.3 with a risk adjustment factor, it contributes zero to a Medicare Advantage beneficiary's V28/V24 community RAF score in either version. Coders should check whether provider documentation supports a more specific child code that does map to a community payment HCC.

Question 5

What should coders know when reporting D38.3?

Accepted Answer

Mediastinal masses have a broad differential diagnosis; ensure pathology confirms uncertain behavior rather than a specific diagnosis Note the anatomic compartment (anterior, middle, or posterior) when documented, as this aids in differential diagnosis

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D38.3

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D38.3 ICD-10-CM Code: Neoplasm of uncertain behavior of mediastinum

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D38.3

Is D38.3 an HCC code?

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