Childhood Carcinoma of Unknown Primary Treatment (PDQ®)–Health Professional Version
Incidence and Clinical Presentation
Children represent less than 1% of all solid cancers of unknown primary site. Because of the age-related incidence of tumor types, embryonal histologies are more common in children.
Cancers of unknown primary site present as a metastatic cancer for which a precise primary tumor site cannot be determined. As an example, lymph nodes at the base of the skull may enlarge in relationship to a tumor that may be on the face or the scalp but is not evident by physical examination or by radiographic imaging. Thus, modern imaging techniques may indicate the extent of the disease but not a primary site. Tumors such as adenocarcinomas, melanomas, and embryonal tumors, like rhabdomyosarcomas and neuroblastomas, may present in this way.
For all patients who present with tumors from an unknown primary site, treatment is directed toward the specific histopathology of the tumor and is age-appropriate for the general type of cancer initiated, irrespective of the site or sites of involvement.
Studies in adults suggest that positron emission tomography (PET) imaging can be helpful in identifying cancers of unknown primary site, particularly in patients whose tumors arise in the head and neck area. A report in adults using fluorine F 18-fludeoxyglucose (18F-FDG) PET-computed tomography (CT) identified 42.5% of primary tumors in a group of cancers of unknown primary site.
The use of gene expression profiling and next-generation sequencing can enhance the ability to identify the putative tissue of origin and guide in the selection of targeted agents for specific mutations.[4-8] In a study of 200 adult patients with carcinomas of unknown primary site, 125 had adenocarcinomas and 75 had carcinomas without features of adenocarcinoma. Genomic alterations were found in 96% of the cases. The most common alterations were TP53 (55%), KRAS (20%), CDKN2A (19%), and MYC (12%). Clinically relevant and potentially actionable mutations included KRAS (20%), CDKN2A (19%), MCL1 (10%), PTEN (7%), PIK3CA (9%), ERBB2 (8%), RICTOR (6%), BRAF (6%), and NF1 (4%). These findings suggest that genomic profiling can help identify potentially actionable targets that could provide clinical benefit for these patients while reducing the complex and costly workup needed to search for a primary tumor site of origin. Despite reports of precision medicine studies in pediatric oncology, none of them have described a case of carcinoma of unknown primary site with a defined or actionable genomic alteration.
- Kuttesch JF, Parham DM, Kaste SC, et al.: Embryonal malignancies of unknown primary origin in children. Cancer 75 (1): 115-21, 1995. [PUBMED Abstract]
- Bohuslavizki KH, Klutmann S, Kröger S, et al.: FDG PET detection of unknown primary tumors. J Nucl Med 41 (5): 816-22, 2000. [PUBMED Abstract]
- Han A, Xue J, Hu M, et al.: Clinical value of 18F-FDG PET-CT in detecting primary tumor for patients with carcinoma of unknown primary. Cancer Epidemiol 36 (5): 470-5, 2012. [PUBMED Abstract]
- Tothill RW, Li J, Mileshkin L, et al.: Massively-parallel sequencing assists the diagnosis and guided treatment of cancers of unknown primary. J Pathol 231 (4): 413-23, 2013. [PUBMED Abstract]
- Varadhachary GR, Talantov D, Raber MN, et al.: Molecular profiling of carcinoma of unknown primary and correlation with clinical evaluation. J Clin Oncol 26 (27): 4442-8, 2008. [PUBMED Abstract]
- Fizazi K, Greco FA, Pavlidis N, et al.: Cancers of unknown primary site: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up. Ann Oncol 26 (Suppl 5): v133-8, 2015. [PUBMED Abstract]
- Greco FA, Lennington WJ, Spigel DR, et al.: Poorly differentiated neoplasms of unknown primary site: diagnostic usefulness of a molecular cancer classifier assay. Mol Diagn Ther 19 (2): 91-7, 2015. [PUBMED Abstract]
- Gatalica Z, Millis SZ, Vranic S, et al.: Comprehensive tumor profiling identifies numerous biomarkers of drug response in cancers of unknown primary site: analysis of 1806 cases. Oncotarget 5 (23): 12440-7, 2014. [PUBMED Abstract]
- Ross JS, Wang K, Gay L, et al.: Comprehensive Genomic Profiling of Carcinoma of Unknown Primary Site: New Routes to Targeted Therapies. JAMA Oncol 1 (1): 40-9, 2015. [PUBMED Abstract]
- Mody RJ, Prensner JR, Everett J, et al.: Precision medicine in pediatric oncology: Lessons learned and next steps. Pediatr Blood Cancer 64 (3): , 2017. [PUBMED Abstract]
Special Considerations for the Treatment of Children With Cancer
Cancer in children and adolescents is rare, although the overall incidence has been slowly increasing since 1975. Referral to medical centers with multidisciplinary teams of cancer specialists experienced in treating cancers that occur in childhood and adolescence should be considered. This multidisciplinary team approach incorporates the skills of the following health care professionals and others to ensure that children receive treatment, supportive care, and rehabilitation that will achieve optimal survival and quality of life:
- Primary care physicians.
- Pediatric surgeons.
- Radiation oncologists.
- Pediatric medical oncologists/hematologists.
- Rehabilitation specialists.
- Pediatric nurse specialists.
- Social workers.
- Child-life professionals.
(Refer to the PDQ Supportive and Palliative Care summaries for specific information about supportive care for children and adolescents with cancer.)
The American Academy of Pediatrics has outlined guidelines for pediatric cancer centers and their role in the treatment of pediatric patients with cancer. At these pediatric cancer centers, clinical trials are available for most types of cancer that occur in children and adolescents, and the opportunity to participate is offered to most patients and their families. Clinical trials for children and adolescents diagnosed with cancer are generally designed to compare potentially better therapy with current standard therapy. Most of the progress made in identifying curative therapy for childhood cancers has been achieved through clinical trials. Information about ongoing clinical trials is available from the NCI website.
Dramatic improvements in survival have been achieved for children and adolescents with cancer. Between 1975 and 2010, childhood cancer mortality decreased by more than 50%. Childhood and adolescent cancer survivors require close monitoring because side effects of cancer therapy may persist or develop months or years after treatment. (Refer to the PDQ summary on Late Effects of Treatment for Childhood Cancer for specific information about the incidence, type, and monitoring of late effects in childhood and adolescent cancer survivors.)
Childhood cancer is a rare disease, with about 15,000 cases diagnosed annually in the United States in individuals younger than 20 years. The U.S. Rare Diseases Act of 2002 defines a rare disease as one that affects populations smaller than 200,000 people. Therefore, all pediatric cancers are considered rare.
The designation of a rare tumor is not uniform among pediatric and adult groups. In adults, rare cancers are defined as those with an annual incidence of fewer than six cases per 100,000 people. They account for up to 24% of all cancers diagnosed in the European Union and about 20% of all cancers diagnosed in the United States.[5,6] Also, the designation of a pediatric rare tumor is not uniform among international groups, as follows:
- A consensus effort between the European Union Joint Action on Rare Cancers and the European Cooperative Study Group for Rare Pediatric Cancers estimated that 11% of all cancers in patients younger than 20 years could be categorized as very rare. This consensus group defined very rare cancers as those with annual incidences of fewer than 2 cases per 1 million people. However, three additional histologies (thyroid carcinoma, melanoma, and testicular cancer) with incidences of more than 2 cases per 1 million people were also included in the very rare group because there is a lack of knowledge and expertise in the management of these tumors.
- The Children's Oncology Group defines rare pediatric cancers as those listed in the International Classification of Childhood Cancer subgroup XI, which includes thyroid cancer, melanoma and nonmelanoma skin cancers, and multiple types of carcinomas (e.g., adrenocortical carcinoma, nasopharyngeal carcinoma, and most adult-type carcinomas such as breast cancer, colorectal cancer, etc.). These diagnoses account for about 4% of cancers diagnosed in children aged 0 to 14 years, compared with about 20% of cancers diagnosed in adolescents aged 15 to 19 years.
Most cancers in subgroup XI are either melanomas or thyroid cancer, with other types accounting for only 1.3% of cancers in children aged 0 to 14 years and 5.3% of cancers in adolescents aged 15 to 19 years.
These rare cancers are extremely challenging to study because of the low number of patients with any individual diagnosis, the predominance of rare cancers in the adolescent population, and the lack of clinical trials for adolescents with rare cancers.
Information about these tumors may also be found in sources relevant to adults with cancer, such as the PDQ summary on Carcinoma of Unknown Primary Treatment.
- Smith MA, Seibel NL, Altekruse SF, et al.: Outcomes for children and adolescents with cancer: challenges for the twenty-first century. J Clin Oncol 28 (15): 2625-34, 2010. [PUBMED Abstract]
- American Academy of Pediatrics: Standards for pediatric cancer centers. Pediatrics 134 (2): 410-4, 2014. Also available online. Last accessed June 7, 2022.
- Smith MA, Altekruse SF, Adamson PC, et al.: Declining childhood and adolescent cancer mortality. Cancer 120 (16): 2497-506, 2014. [PUBMED Abstract]
- Ward E, DeSantis C, Robbins A, et al.: Childhood and adolescent cancer statistics, 2014. CA Cancer J Clin 64 (2): 83-103, 2014 Mar-Apr. [PUBMED Abstract]
- Gatta G, Capocaccia R, Botta L, et al.: Burden and centralised treatment in Europe of rare tumours: results of RARECAREnet-a population-based study. Lancet Oncol 18 (8): 1022-1039, 2017. [PUBMED Abstract]
- DeSantis CE, Kramer JL, Jemal A: The burden of rare cancers in the United States. CA Cancer J Clin 67 (4): 261-272, 2017. [PUBMED Abstract]
- Ferrari A, Brecht IB, Gatta G, et al.: Defining and listing very rare cancers of paediatric age: consensus of the Joint Action on Rare Cancers in cooperation with the European Cooperative Study Group for Pediatric Rare Tumors. Eur J Cancer 110: 120-126, 2019. [PUBMED Abstract]
- Pappo AS, Krailo M, Chen Z, et al.: Infrequent tumor initiative of the Children's Oncology Group: initial lessons learned and their impact on future plans. J Clin Oncol 28 (33): 5011-6, 2010. [PUBMED Abstract]
- Howlader N, Noone AM, Krapcho M, et al., eds.: SEER Cancer Statistics Review, 1975-2012. National Cancer Institute, 2015. Also available online. Last accessed May 25, 2022.
Treatment of Childhood Carcinoma of Unknown Primary
Chemotherapy, targeted therapy, and radiation therapy treatments appropriate and relevant for the general category of carcinoma or sarcoma (depending on the histological findings, symptoms, and extent of tumor) are initiated as early as possible.
(Refer to the PDQ summary on adult Carcinoma of Unknown Primary Treatment for more information.)
- Morris GJ, Greco FA, Hainsworth JD, et al.: Cancer of unknown primary site. Semin Oncol 37 (2): 71-9, 2010. [PUBMED Abstract]
Treatment Options Under Clinical Evaluation for Childhood Carcinoma of Unknown Primary
Information about National Cancer Institute (NCI)–supported clinical trials can be found on the NCI website. For information about clinical trials sponsored by other organizations, refer to the ClinicalTrials.gov website.
The following is an example of a national and/or institutional clinical trial that is currently being conducted:
- APEC1621 (NCT03155620) (Pediatric MATCH: Targeted Therapy Directed by Genetic Testing in Treating Pediatric Patients with Relapsed or Refractory Advanced Solid Tumors, Non-Hodgkin Lymphomas, or Histiocytic Disorders): NCI-COG Pediatric Molecular Analysis for Therapeutic Choice (MATCH), referred to as Pediatric MATCH, will match targeted agents with specific molecular changes identified in a patient's tumor (refractory or recurrent). Children and adolescents aged 1 to 21 years are eligible for the trial.
Patients with tumors that have molecular variants addressed by treatment arms included in the trial will be offered treatment on Pediatric MATCH. Additional information can be obtained on the NCI website and ClinicalTrials.gov website.
Changes to This Summary (02/23/2022)
The PDQ cancer information summaries are reviewed regularly and updated as new information becomes available. This section describes the latest changes made to this summary as of the date above.
Editorial changes were made to this summary.
This summary is written and maintained by the PDQ Pediatric Treatment Editorial Board, which is editorially independent of NCI. The summary reflects an independent review of the literature and does not represent a policy statement of NCI or NIH. More information about summary policies and the role of the PDQ Editorial Boards in maintaining the PDQ summaries can be found on the About This PDQ Summary and PDQ® - NCI's Comprehensive Cancer Database pages.
About This PDQ Summary
Purpose of This Summary
This PDQ cancer information summary for health professionals provides comprehensive, peer-reviewed, evidence-based information about the treatment of pediatric carcinoma of unknown primary. It is intended as a resource to inform and assist clinicians in the care of their patients. It does not provide formal guidelines or recommendations for making health care decisions.
Reviewers and Updates
This summary is reviewed regularly and updated as necessary by the PDQ Pediatric Treatment Editorial Board, which is editorially independent of the National Cancer Institute (NCI). The summary reflects an independent review of the literature and does not represent a policy statement of NCI or the National Institutes of Health (NIH).
Board members review recently published articles each month to determine whether an article should:
- be discussed at a meeting,
- be cited with text, or
- replace or update an existing article that is already cited.
Changes to the summaries are made through a consensus process in which Board members evaluate the strength of the evidence in the published articles and determine how the article should be included in the summary.
The lead reviewers for Childhood Carcinoma of Unknown Primary Treatment are:
- Denise Adams, MD (Children's Hospital Boston)
- Karen J. Marcus, MD, FACR (Dana-Farber Cancer Institute/Boston Children's Hospital)
- Paul A. Meyers, MD (Memorial Sloan-Kettering Cancer Center)
- Thomas A. Olson, MD (Aflac Cancer and Blood Disorders Center of Children's Healthcare of Atlanta - Egleston Campus)
- Alberto S. Pappo, MD (St. Jude Children's Research Hospital)
- Arthur Kim Ritchey, MD (Children's Hospital of Pittsburgh of UPMC)
- Carlos Rodriguez-Galindo, MD (St. Jude Children's Research Hospital)
- Stephen J. Shochat, MD (St. Jude Children's Research Hospital)
Any comments or questions about the summary content should be submitted to Cancer.gov through the NCI website's Email Us. Do not contact the individual Board Members with questions or comments about the summaries. Board members will not respond to individual inquiries.
Levels of Evidence
Some of the reference citations in this summary are accompanied by a level-of-evidence designation. These designations are intended to help readers assess the strength of the evidence supporting the use of specific interventions or approaches. The PDQ Pediatric Treatment Editorial Board uses a formal evidence ranking system in developing its level-of-evidence designations.
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The preferred citation for this PDQ summary is:
PDQ® Pediatric Treatment Editorial Board. PDQ Childhood Carcinoma of Unknown Primary Treatment. Bethesda, MD: National Cancer Institute. Updated <MM/DD/YYYY>. Available at: https://www.cancer.gov/types/unknown-primary/hp/child-unknown-primary-treatment-pdq. Accessed <MM/DD/YYYY>.
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