Types of Lung Cancer: NSCLC, SCLC and Subtypes

Not all lung cancers are the same.

The type of lung cancer determines which treatments are likely to work, how quickly the disease may progress, and what to expect at each stage of care.

This guide covers the two main categories, their subtypes, and the biomarkers that decide whether targeted therapy is an option.

types of lung cancer
types of lung cancer
Written by Katrina Metz, RT·Medically reviewed by Dr. Claudia LeBlanc, MD·Last updated

Key Takeaways

  • Lung cancer is divided into two main categories: non-small cell lung cancer (NSCLC), about 80-85% of cases in Canada, and small cell lung cancer (SCLC), about 13-15%.
  • Adenocarcinoma is the most common NSCLC subtype at roughly 40% of cases, and the one most likely to carry a targetable genetic change.
  • Different types respond to completely different treatments, which is why biopsy and molecular testing are standard parts of diagnosis.
  • Comprehensive biomarker testing (NGS) is now recommended for all patients with non-squamous NSCLC.
  • About 3-5% of people with NSCLC have an ALK gene rearrangement, rising to over 20% in patients under 40.

Table of Contents

Not all lung cancers are the same. The type of lung cancer a person has determines which treatments are likely to work, how quickly the disease may progress, and what to expect at each stage of care.

There are two main categories: non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). Within these, there are some subtypes driven by specific genetic alterations, like ALK, EGFR, etc. These subtypes usually respond to targeted therapies.

Non-Small Cell Lung Cancer (NSCLC)

NSCLC is the most common type, making up about 80-85% of all lung cancer cases in Canada:

  • Adenocarcinoma is the most common subtype, accounting for roughly 40% of cases. It typically forms in the outer parts of the lung and is the type most often seen in people who have never smoked. It is more common in women than men and is the subtype most likely to carry a targetable genetic change.
  • Squamous cell carcinoma accounts for about 25-30% of NSCLC. It usually forms near the central airways and is strongly linked to tobacco smoking.
  • Large cell carcinoma can appear anywhere in the lung and tends to grow faster than other NSCLC subtypes.

Small Cell Lung Cancer (SCLC)

SCLC makes up about 13-15% of all cases. It is almost always caused by heavy smoking and grows and spreads faster than NSCLC.

Doctors describe SCLC using two stages: limited (confined to one lung and nearby lymph nodes) and extensive (spread beyond). SCLC often responds well to chemotherapy and radiation initially, but usually comes back because of its aggressive nature. It’s hard to cure.

Why the Type of Lung Cancer Matters

Different types respond to completely different treatments. Targeted therapy drugs only work when the cancer has a specific genetic change. This is why biopsy and molecular testing are standard parts of the diagnostic process, not just to confirm cancer, but to identify which subtype and which treatments may work.

Molecular Subtypes and Biomarkers for NSCLC

Once NSCLC is confirmed, the biopsy tissue is tested for specific genetic changes called biomarkers or driver mutations. Common ones include:

  1. EGFR: most common targetable mutation; treated with EGFR inhibitors such as Osimertinib
  2. ALK: present in 3-5% of NSCLC; more common in younger patients and non-smokers; treated with ALK inhibitors including Lorlatinib and Alectinib
  3. ROS1: present in about 1-2% of NSCLC; similar clinical profile to ALK-positive disease
  4. KRAS: one of the most common mutations in adenocarcinoma; targeted drugs now available such as Sotorasib
  5. BRAF, RET, MET, HER2, NTRK: less common, but increasingly targetable
  6. PD-L1: not a mutation, but can guide the choice of treatment

Comprehensive biomarker testing (next-generation sequencing or NGS) is now recommended for all patients with non-squamous NSCLC.

Spotlight: ALK-Positive NSCLC

About 3-5 percent of people with NSCLC have an ALK gene rearrangement. This proportion is much higher in younger patients, over 20% in patients under 40. It is more common in non-smokers and in those with adenocarcinoma.

Patients with ALK-positive NSCLC are treated with ALK tyrosine kinase inhibitors (TKIs). Up to 75% of ALK-positive NSCLC patients develop brain metastases at some point, making CNS-penetrating drugs like Lorlatinib especially important.

Managing Lorlatinib well requires close attention to its side effects, including weight gain, peripheral edema, neuropathy, cognitive changes, and hyperlipidemia. These are manageable with the right clinical support.

Free Video Education Series

RESPIPLUS has produced a 12-part video series on ALK-positive non-small cell lung cancer for healthcare professionals, covering diagnosis, treatment selection and the day-to-day management of targeted therapy.

Watch the Lung Cancer Video Series →

Questions to Ask Your Healthcare Team

  • What type and subtype of lung cancer is it exactly?
  • Has molecular or biomarker testing been done? What were the results?
  • Is targeted therapy an option for my type of cancer?
  • What stage is the cancer, and has it spread?

Related Resources

References

Show references
  1. American Cancer Society. What Is Lung Cancer? cancer.org
  2. American Cancer Society. Key Statistics for Lung Cancer. cancer.org
  3. Cleveland Clinic. Lung Cancer: Types, Stages, Symptoms, Diagnosis and Treatment. clevelandclinic.org
  4. Mayo Clinic. Lung Cancer. Symptoms and Causes. mayoclinic.org
  5. MD Anderson Cancer Center. Lung Cancer. mdanderson.org
  6. Chia PL et al. Prevalence and natural history of ALK-positive non-small-cell lung cancer and the clinical impact of targeted therapy. Clin Epidemiol. 2014;6:423–432. PubMed
  7. Rothwell C et al. Anaplastic lymphoma kinase rearrangement prevalence in patients with advanced NSCLC in the United States: retrospective real world data. BMC Cancer 2021. PMC
  8. Canadian Cancer Society. 5 Facts About Lung Cancer in Canada. 2023. cancer.ca

About this article

Written by Katrina Metz, RT, respiratory therapist and medical writer at RESPIPLUS. Medically reviewed by Dr. Claudia LeBlanc, MD, Senior Scientist at Princess Margaret Cancer Centre and a leading Canadian expert in ALK-positive NSCLC management.

About this project
This series was supported by Pfizer and developed independently by RESPIPLUS with the CARMA-BROS network. Scientific Committee: Dr. Geoffrey Liu (Princess Margaret), Maria Sedeno (RESPIPLUS), Emily Horvat (RESPIPLUS), Katrina Metz (RESPIPLUS), Christopher Deutschman (CARMA-BROS), Faisal Al Agha (CARMA-BROS). All materials are free and permanently hosted on chroniclungdiseases.com.

Published August 4, 2026. Last reviewed . For educational purposes only. Not a substitute for medical advice.