Adenocarcinoma of the lung is the most common type of lung cancer.
Pulmonology Term
In Short
Edited by Charles L. Fishman, MD
Adenocarcinoma of the lung is the most common type of lung cancer. It is a malignancy arising from the bronchial glands. It is associated with tobacco use.
Synonyms (AKA):
bronchogenic adenocarcinoma
adenocarcinoma of lung
NSCLC (see summary table below)
Pathology: There are different subtypes of bronchogenic adenocarcinoma that have been shown to be associated with prognosis.
Atypical adenomatous hyperplasia is a focal lesion of atypical type II pneumocytes and is thought to be premalignant.
Adenocarcinoma in situ (formerly known as Bronchoalveolar Carcinoma) demonstrates lepidic growth (meaning along the lining) of atypical type II pneumocytes or Clara cells along septae and does not invade stroma, vasculature, or pleura.
Minimally invasive adenocarcinoma also demonstrates lepidic growth, but is distinguished from adenocarcinoma in situ by invasion into the stroma, vasculature, or pleura of less than 5 mm.
Invasive adenocarcinomas invade the stroma by greater than 5 mm.
Prognosis
The most important determinant of prognosis is stage of disease at diagnosis. Early-stage disease may be resected for cure. Disease invading the lymph nodes, pleura and distant sites is rarely curable. Many studies have examined the relationship between histological subtypes of adenocarcinoma and prognosis. The less aggressive histologic sub types are less likely to spread, and confer a better prognosis
Symptoms
The severity of symptoms depends on the progression of the disease. Early onset disease may be asymptomatic and only detected incidentally by imaging of the chest. Symptoms may include cough, hemoptysis, and general constitutional symptoms including weight loss and night sweats. Patients may have pleural effusions contributing to shortness of breath and decreased lung sounds.
Diagnosis
Lung cancer screening with low dose chest CT may allow for early detection of lung nodules. Biopsy provides the definitive diagnosis. Image guided or bronchoscopic biopsies may be done, depending on the location of the lesions present. For staging purposes, the most distant site of disease should be sampled.
The differential diagnosis includes other types of lung cancer, such as small cell lung cancer and squamous cell lung cancer. Granulomas and hamartomas are also included on the differential. The histology of the sample determines the definitive diagnosis.
Treatment Options
If localized, bronchogenic adenocarcinoma is typically treated with surgical resection. If the disease is not amenable to resection, radiotherapy and chemotherapy are effective but rarely curative. A full immunodiagnostic panel is also done to look for molecular targets for immunotherapy.
Recent studies have shown improved survival using immunotherapy in combination with chemotherapy as compared to chemotherapy alone. Improvement in survival was seen in both early-stage lung cancer and in metastatic cancer although the benefits of combination therapy seem to be better in early-stage cancer. Additionally, for patients with PDL-1 positive tumors, immunotherapy has been shown to be superior to chemotherapy, both in adverse events and in improving survival. Recent studies have demonstrated that chemotherapy can be avoided for some patients with metastatic NSCLC. Survival and duration of response increases as PDL-1 expression increases. Although even for patients that are PDL-1 negative (<1%) or have PDL-1 (1–49%) tumors, immunotherapy/chemotherapy combination strategies appear to be the new standard of care as first line treatment. In one study, the combination of chemotherapy and immunotherapy yielded an overall survival of 22 months in metastatic NSCLC and reduced the risk of death by 44% compared to chemotherapy alone.
Lung Carcinoma (summary table)
SCLC
small cell carcinoma (oat cell cancer)
combined small cell carcinoma
neuroendocrine lung cancer
NSCLC
adenocarcinoma
squamous cell carcinoma
large cell carcinoma
Other
neuroendocrine large cell lung cancer (a more aggressive form of neuroendocrine tumors)
References:
Latimer, K., Mott, T. Lung cancer: diagnosis, treatment principles, and screening. Am Fam Physician. 2015 Feb 15;91(4):250-256.
Hutchinson, B., Shroff, G., Truong, M., et al. Spectrum of Lung Adenocarcinoma. Seminars in Ultrasound, CT, and MRI. 2019; 40 (3): 255-264.
Travis, W., Brambilla, E., Nicholson, A., et al. The 2015 World Health Organization Classification of Lung Tumors: Impact of Genetic, Clinical, and Radiologic Advances Since the 2004 Classification. Journal of Thoracic Oncology. 2015; 10(9): 1243-1260.
Wang, Y., Li, C., Wang, Z. et al. Comparison between immunotherapy efficacy in early non-small cell lung cancer and advanced non-small cell lung cancer: a systematic review. BMC Med 20, 426 (2022). https://doi.org/10.1186/s12916-022-02580-1
Mithoowani, H., Febbraro, M. Non-Small-Cell Lung Cancer in 2022: A Review for General Practitioners in Oncology. Curr Oncol. 2022 Mar; 29(3): 1828–1839. Published online 2022 Mar 9. doi: 10.3390/curroncol29030150
Gadgeel S., Rodríguez-Abreu D., Speranza G., Esteban E., Felip E., Dómine M., Hui R., Hochmair M.J., Clingan P., Powell S.F., et al. Updated Analysis From KEYNOTE-189: Pembrolizumab or Placebo Plus Pemetrexed and Platinum for Previously Untreated Metastatic Nonsquamous Non-Small-Cell Lung Cancer. J. Clin. Oncol. 2020;38:1505–1517. doi: 10.1200/JCO.19.03136.