ICD-10 Code D43.1 – Neoplasm of uncertain behavior of brain, infratentorial (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code D43.1 – Neoplasm of uncertain behavior of brain, infratentorial
What it is
D43.1 identifies a brain tumor in the infratentorial region, such as the cerebellum or brainstem, when its behavior is uncertain. Use it when the pathology or clinical record does not clearly show benign or malignant behavior.
Clinical signs
Clinical features vary; refer to documentation. Patients may have findings from posterior fossa or brainstem involvement, such as headache, balance problems, nausea, or cranial nerve deficits, but the diagnosis rests on documented tumor location and uncertain behavior.
When to use this code
Use D43.1 when the provider documents an infratentorial brain neoplasm with uncertain behavior and the site is specified. It is appropriate for pathology reports, imaging impressions, or operative notes that confirm the lesion but do not classify it as benign or malignant. Check documentation if the exact behavior is unclear.
Do not use for
Do not use this code for clearly benign or malignant brain tumors, or for neoplasms outside the infratentorial region. If the record only says “brain tumor” without location or behavior, check documentation before coding.
Coding tip
Confirm both the uncertain behavior and the infratentorial site before assigning D43.1.