ICD-10 Code D40.1 – Neoplasm of uncertain behavior of testis (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code D40.1 – Neoplasm of uncertain behavior of testis
What it is
D40.1 identifies a testicular neoplasm whose behavior is uncertain, meaning the pathology or clinical picture does not clearly show benign or malignant behavior. Use it when the record documents a testicular mass or tumor with uncertain biologic behavior.
Clinical signs
Clinical features vary; refer to documentation. Common findings may include a testicular mass, swelling, asymmetry, or an incidental imaging abnormality, but the code is based on the documented uncertain behavior, not symptoms alone.
When to use this code
Use D40.1 when the provider documents a neoplasm of the testis with uncertain behavior, borderline behavior, or indeterminate malignant potential. It also fits when pathology or operative notes describe the lesion as uncertain and the final diagnosis names the testis as the site.
Code this only when the documentation supports the testis as the primary site. If the record instead identifies a clearly benign or malignant tumor, or the site is not confirmed, check documentation before assigning D40.1.
Do not use for
Do not use this code for clearly malignant testicular cancer, benign testicular lesions, or nonspecific testicular pain without a documented neoplasm. Check documentation if the exact behavior or site is unclear.
Coding tip
Verify both the anatomic site and the phrase “uncertain behavior” in the final diagnosis before coding D40.1.