How to code an untreated primary malignancy as a personal history of malignancy in ICD-10-CM documentation

When a chart shows a primary malignancy that isn’t being treated right now, how should you classify it in ICD-10-CM? You might think the answer depends on whether the cancer will come back or if it’s somehow lurking in the shadows. In reality, the labeling hinges on the patient’s current disease activity and what the documentation says. The correct choice is: As a personal history of malignancy.

Let me explain why this is the right fit, and what it means for everyday coding.

What “history” really means in ICD-10-CM terms

Think of cancer documentation as a story with chapters. One chapter covers the diagnosis itself — the malignancy that was found, diagnosed, and treated at some point. The next chapters describe what happened after treatment: did the cancer go away, stay the same, or reappear? In ICD-10-CM, a history of malignancy is coded when the cancer has been treated or removed and is no longer active. Even if the primary tumor still exists in the body, if there’s no current treatment and no active disease being managed, the code that captures past cancer belongs to the “personal history” category.

That distinction is not just pedantic trivia. It guides follow-up care, screening intervals, and the patient’s medical narrative. It also helps other clinicians understand the patient’s risk for recurrence, potential late effects of treatment, and what to watch for in the future. In other words, the history code is a signal that the cancer is part of the patient’s past story, not the headline of today’s medical care.

Why not the other options?

• A recurrent condition: This would imply the cancer has returned after treatment and is currently active again. If the chart clearly shows no active disease or ongoing treatment, “recurrent” isn’t accurate. The logic is simple: recurrence means treatment is once more on the table in response to a comeback, not a dormant past.

• C incidental finding: An incidental finding is something discovered unintentionally, unrelated to the current complaint or reason for the visit. A history of a treated cancer is a deliberate medical history, not an unrelated blip found by chance.

• D complication: A complication would be something that arises because of a condition or its treatment and complicates the care plan. If the patient’s primary cancer isn’t being treated and there’s no new problem caused by it that changes management, labeling it a complication wouldn’t fit.

How this plays out in the chart

Let’s make it practical with a common scenario. Suppose a patient was diagnosed with a primary breast cancer five years ago, underwent surgery and chemotherapy, and now has no active disease being treated. The chart notes say the patient is “in remission” and there’s no current cancer-directed therapy. In this case, you’d encode the patient with a personal history of malignant neoplasm, site-specified if the documentation provides the cancer site. The general idea is this: the history code marks the prior cancer as part of the patient’s medical history, not as an active problem to be treated today.

If the site is known, many coders use the site-specific history code (for example, a code family like Z85.3 for a personal history of malignant neoplasm of breast, if that’s the documented site). If the site isn’t clear or isn’t specified in the chart, you’d use the broader, non-site-specific history code in accordance with your coding guidelines. The upshot: the current clinical focus remains on current problems, but the patient’s cancer history still appears in the record for context and surveillance planning.

Documentation matters more than you might think

The voice of the chart matters. When the clinician writes “history of breast cancer treated in 2018, currently in remission, no evidence of disease,” it’s a green light for the history code. If, however, the note says “breast cancer, currently untreated,” that could signal a different situation that might require an active cancer code or a separate note about the lack of treatment. The key is to align coding with what the documentation actually states.

That’s why a quick, respectful audit of the chart helps. Look for phrases like:

• “in remission,” “no evidence of disease,” “completed treatment”

• “history of,” “previously treated,” “follow-up after cancer”

• “not currently receiving cancer therapy,” or “cancer surveillance only”

These phrases are the breadcrumbs that point you toward the correct code.

A few quick tips to keep you sharp

• Always verify if the cancer is active: If there’s active treatment, a current cancer code may be appropriate. If not, a history code is typically preferred.

• Use site-specific history codes when the documentation identifies the tumor site clearly. A general history code can work when the site isn’t documented.

• Don’t conflate recurrence with history. If you truly have documented recurrence, you’ll be coding for active disease or a new treatment phase, not historical memory.

• Pair the history code with the patient’s current problem list. The history of cancer provides context for surveillance and risk, but it doesn’t replace the need to code other active conditions.

A moment of practical nuance

Here’s a tiny but real-world nuance that can trip people up: a patient who had a primary cancer that’s been treated and shows no signs of disease but later develops metastases in a different organ from the original site. If the metastatic spread is being actively treated, the proper approach is to code the active metastatic disease. If there’s no active cancer activity related to that metastatic process at the moment, you still treat the original history as such. Documentation is king here; the notes should clearly separate “historical cancer” from “current metastasis treatment.”

Why this matters for patient care

Beyond the coding desk, using the correct historical label supports the care team in meaningful ways. It helps the primary care physician and oncologists set the right follow-up cadence—screening intervals, imaging, and lab tests tailored to someone who had cancer in their past. It also informs patient education: someone who carries a history of cancer may need ongoing counseling about risk, lifestyle choices, and early warning signs to watch for.

A light note on the “why now” factor

You might wonder why this distinction exists in today’s medical world, where data flows quickly and care teams keep tabs on everything. The truth is that a clean, well-documented history of illness helps prevent miscommunication. It avoids unnecessary alarms about active disease and prevents the misinterpretation that an old cancer is the same as an active cancer. In short, it keeps care precise and calm, which is especially valuable for patients who carry a heavy medical history.

How to explain it to someone outside the field

If you’re talking with a patient or a non-clinician colleague, you can frame it like this: “The cancer they had in the past is a part of their medical history, but it isn’t the problem we’re treating today.” The history code is like a bookmark in the patient’s medical story, reminding future clinicians of what happened without making today’s care hinge on yesterday’s diagnosis.

A final thought to carry forward

When a primary malignancy isn’t being treated, coding it as a personal history of malignancy is not a shrug of the shoulders. It’s a thoughtful, guideline-based choice that reflects the patient’s current disease activity and supports better continuity of care. The other options—recurrence, incidental finding, and complication—have their places, but they don’t fit this particular scenario once the chart confirms no active disease or ongoing cancer therapy.

If you’re navigating this kind of chart, remember: the clearest path is to match your code to the documented state of disease today. History codes acknowledge what happened, while active disease codes capture what’s happening now. When you keep that distinction straight, you’re not just coding accurately—you’re helping a patient receive the right follow-up, the right screenings, and the right care path for years to come.