ICD-10 Code D01.1 – Carcinoma in situ of rectosigmoid junction (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code D01.1 – Carcinoma in situ of rectosigmoid junction
What it is
D01.1 identifies carcinoma in situ at the rectosigmoid junction, meaning abnormal epithelial cells are confined to the mucosal lining and have not invaded deeper tissue. Use it when documentation specifically states carcinoma in situ at this site.
Clinical signs
Clinical features vary; refer to documentation. Diagnosis is usually based on pathology showing malignant-appearing cells limited to the epithelium, without invasion through the basement membrane.
When to use this code
Use this code when the provider documents carcinoma in situ of the rectosigmoid junction, including biopsy or excision findings at that exact location. It is appropriate when the record confirms a noninvasive neoplastic process and does not describe invasive colorectal cancer. If the site is unclear, check documentation.
Do not use for
Do not use D01.1 for invasive carcinoma, dysplasia without carcinoma in situ, or lesions documented only as malignant neoplasm of colon or rectum. Check documentation if the pathology report does not specify the rectosigmoid junction.
Coding tip
Match the code to the documented anatomic site and confirm the term “in situ” appears in the pathology or provider note.