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Understanding Findings

Lung Nodule Size Chart and When to Worry

A clear lung nodule size chart for CT findings: <4 mm, 4-6 mm, 6-8 mm, >8 mm, growth criteria, cancer risk features, and Fleischner follow-up.

CT Read Editorial10 min readPublished 2026-05-05

Reviewed by a board-certified radiologist

Lung Nodule Size Chart and When to Worry medical imaging guide cover
Radiologist reviewing chest CT lung window images with a pulmonary nodule
Synthetic editorial illustration for patient education. Not a real patient study or diagnosis.

Before You Read

Use this article as a plain-language guide, not a diagnosis

This guide explains common imaging terms, patterns, and follow-up questions so you can better understand your radiology report. Always confirm important findings with your radiologist or treating clinician.

Introduction

A lung nodule is a round or oval spot on the lung that is 30 mm or less in diameter. Most nodules are benign, representing old scars, lymph nodes, or infections.

Nodule Size Follow-Up Guide (Fleischner Criteria)

  • < 4 mm: Low malignancy risk (<1%). Routine follow-up is generally not required in low-risk individuals.
  • 4 to 6 mm: Repeat CT scan at 12 months to verify stability.
  • 6 to 8 mm: Repeat CT scan at 6-12 months, and again at 18-24 months.
  • > 8 mm: Increased risk. Requires closer follow-up at 3 months, PET-CT, or tissue biopsy.

Frequently asked questions

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