Rectal Cancer ICD-10-CM Codes

Explore valid ICD-10 codes for rectal cancer, including C19 and C20. Learn about diagnosis, treatment, billing, and clinical documentation guidelines.

By Wynona Jugueta on Aug 8, 2025.

Fact Checked by Gale Alagos.

Use Code

What ICD-10 codes are used for rectal cancer?

Rectal cancer is a malignant neoplasm that originates in the tissues of the rectum—the final section of the large intestine, located just above the anal canal. It represents a significant health burden, and accurate ICD-10 coding is vital for effective reporting, clinical documentation, and treatment planning. Healthcare professionals must ensure that the codes reflect the site and type of tumor and its relationship with other organs, systems, and medical history.

Below are the most commonly used rectal cancer ICD-10 codes, along with their meanings:

C19 – Malignant neoplasm of rectosigmoid junction: This code refers to a cancerous growth located between the rectum and sigmoid colon—a common overlapping site for colorectal malignancies.

C20 – Malignant neoplasm of rectum: Used when a malignant tumor, such as a malignant melanoma or malignant carcinoid tumor, is found specifically within the rectum.
C78.5 – Secondary malignant neoplasm of large intestine and rectum: Indicates metastatic cancer that has spread to the rectum or large intestine from the stomach, bronchus, or other organs.
Z85.048 – Personal history of malignant neoplasm of rectum: Captures the patient’s history of rectal cancer, important for follow-up and surveillance, though not active disease.
Z85.038 – Personal history of malignant neoplasm of rectosigmoid junction: Used for patients with a resolved malignancy in the rectosigmoid junction; crucial for long-term care documentation.
Z85.098 – Personal history of other malignant neoplasms of the large intestine: Applies to prior cancers in other intestinal regions such as the hepatic flexure, splenic flexure, or ascending colon.

Which rectal cancer ICD codes are billable?

C19: Yes, billable. Accurately captures cancer at a specific location—rectosigmoid junction.
C20: Yes, billable. Represents rectal cancer, vital for diagnosis, treatment, and reimbursement.
C78.5: Yes, billable. Essential for coding secondary malignant neoplasms, especially when tumors have spread to the rectum or large intestine from other organs.
Z85.048: No, not billable. Reflects personal history of rectal cancer, not an active disease requiring treatment.
Z85.038: No, not billable. Used for follow-up documentation after resolution of cancer in the rectosigmoid junction.
Z85.098: No, not billable. Indicates previous malignant neoplasms in large intestine regions like the hepatic flexure or splenic flexure, but not current disease.

Clinical information

Rectal cancer is an aggressive malignant neoplasm that can originate from glandular cells or rarer types like malignant melanoma or malignant carcinoid tumor. This cancer affects the body’s digestive system, especially the distal large intestine and anus.

Risk factors and causes

Rectal cancer typically develops in older adults but is increasingly seen in younger individuals. Contributing factors include:

Family history of colorectal cancer
Inflammatory bowel disease
Genetic syndromes (e.g., FAP or Lynch syndrome)
Sedentary lifestyle
High consumption of red or processed meats

Common symptoms

Patients may experience:

Blood in the stool
Abdominal discomfort
Altered bowel habits
Fatigue and unexplained weight loss

These symptoms often lead to clinical contact and prompt further testing.

Diagnosis

Healthcare professionals rely on:

Physical exams and patient history
Lab tests and tumor markers
Imaging (colonoscopy, sigmoidoscopy, CT scans)
Biopsy for definitive reporting

Treatment options

Treatment depends on the cancer’s location, such as near the hepatic flexure, splenic flexure, or more distal sections like the anal canal. Common treatments include:

Surgical resection (e.g., low anterior resection)
Chemotherapy and radiation
Immunotherapy for specific genetic markers
Follow-up care using non-billable Z85 codes for tracking recovery or recurrence

Prognosis and monitoring

Outcomes vary based on stage and metastasis to other organs. Early documentation, routine screening, and accurate ICD-10 usage are key for improving survival and quality of life.

Synonyms include:

Colorectal cancer
Rectal carcinoma
Cancer of the rectum
Rectal malignancy
Adenocarcinoma of the rectum

Commonly asked questions

Healthcare professionals use ICD codes for rectal cancer to document diagnoses, guide treatment plans, and ensure accurate billing and insurance reimbursement. The code selected should match the tumor’s location, whether it's in the rectum, rectosigmoid junction, or a metastatic site.

ICD-10 codes do not specify cancer stages directly, but stage information is typically documented separately using TNM classification systems or cancer staging guidelines. ICD codes focus on the anatomical site and malignancy type rather than disease progression.

Yes, ICD codes are used globally as part of the World Health Organization’s international classification system for diseases. However, countries may have their own adaptations (like ICD-10-CM in the U.S.) for clinical detail and billing standards.

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