Unusual Cancers of Childhood: Types, Symptoms, Diagnosis, and Treatment — Overview, Diagnosis & Treatment Options | MyMedicPlus

The term 'unusual cancers of childhood' encompasses a heterogeneous group of malignancies that are rare in the pediatric population — either because they are uncommon in any age group, or because they more typically affect adults. These include adrenocortical carcinoma (ACC), nasopharyngeal carcinoma (NPC), carcinoid tumors of the gastrointestinal tract, colorectal adenocarcinoma, melanoma, thyroid carcinoma, hepatocellular carcinoma, pancreatic carcinoma, mesothelioma, primary bone sarcomas other than osteosarcoma and Ewing sarcoma, rare CNS tumors, and multiple endocrine neoplasia syndromes. Together, these unusual cancers account for approximately 15–20% of all childhood malignancies. They present unique diagnostic challenges — symptoms often mimic more common pediatric conditions, and clinical experience with these tumors in childhood is limited. Treatment requires adaptation of adult oncology protocols to the pediatric context, with heightened attention to growth, development, and long-term toxicity. All children with unusual cancers should be managed at pediatric oncology centers with access to specialist multidisciplinary teams, and enrollment in clinical trials is strongly encouraged to improve evidence-based treatment for these rare entities.

The causes of unusual childhood cancers vary by tumor type. Adrenocortical carcinoma (ACC) in children under 4 years is highly associated with germline TP53 mutations (Li-Fraumeni syndrome) — particularly the R337H TP53 mutation endemic in southern Brazil, which has a >90% ACC penetrance in childhood. Beckwith-Wiedemann syndrome (BWS, IGF2 imprinting abnormality) predisposes to hepatoblastoma and Wilms tumor, and rarely ACC. Nasopharyngeal carcinoma in children and adolescents (particularly East Asian origin) is associated with Epstein-Barr virus (EBV) infection — similar to adult NPC. Multiple endocrine neoplasia type 1 (MEN1, menin gene) and type 2 (MEN2, RET proto-oncogene) predispose to a range of endocrine tumors including thyroid medullary carcinoma, pituitary adenoma, and parathyroid disease. Familial adenomatous polyposis (FAP, APC gene) causes colorectal adenoma from early childhood and colorectal carcinoma, hepatoblastoma, and desmoid tumors. Werner syndrome, Bloom syndrome, and Rothmund-Thomson syndrome predispose to various pediatric malignancies. Prior ionizing radiation (e.g., for prior childhood cancer treatment) increases risk of secondary malignancies including thyroid carcinoma and bone sarcomas. The majority of unusual childhood cancers occur sporadically without identifiable predisposing genetic conditions.

Symptoms vary dramatically by tumor type and location. Adrenocortical carcinoma presents with virilization (clitoral enlargement, pubic hair, voice deepening in girls), Cushing syndrome (central obesity, hypertension, striae, glucose intolerance), or as an incidentally detected adrenal mass. Nasopharyngeal carcinoma in adolescents presents with painless cervical lymphadenopathy, nasal obstruction, epistaxis, hearing loss (Eustachian tube dysfunction), and cranial nerve palsies in locally advanced disease. Colorectal adenocarcinoma — rare but biologically aggressive in children — presents with rectal bleeding, change in bowel habit, abdominal pain, and anemia; it is more often found at advanced stage than in adults as suspicion is low. Thyroid carcinoma (papillary type, the most common in children) presents as a painless thyroid nodule or cervical lymphadenopathy; it is associated with higher rates of lymph node and lung metastases than in adults but remains highly curable. Carcinoid tumors of the appendix are often incidental findings at appendectomy for appendicitis; small bowel and other GI carcinoids may cause carcinoid syndrome (flushing, diarrhea, wheezing) when metastatic. Melanoma in adolescents most commonly arises in giant congenital melanocytic nevi or de novo, presenting as a changing pigmented lesion, asymmetric nodule, or ulcerating skin lesion. General cancer warning signs in children — the CEWKI mnemonic: Continued unexplained weight loss; Headaches with early morning vomiting; Increasing swelling or persistent pain in bones, joints, back, or legs; Lump or mass in the abdomen, neck, chest, pelvis, or armpits; Unusual, persistent or significant bleeding or bruising — should prompt urgent evaluation.

Diagnosis of unusual childhood cancers requires a high index of clinical suspicion, as these tumors are rarely considered in the initial differential diagnosis. For adrenocortical carcinoma: CT or MRI of abdomen and pelvis characterizes adrenal mass morphology; serum cortisol (with overnight dexamethasone suppression testing), DHEAS, testosterone, aldosterone, and 17-hydroxyprogesterone determine hormonal secretory status; pathological assessment uses Weiss scoring system on resected specimens. For nasopharyngeal carcinoma: nasopharyngoscopy with biopsy; MRI head and neck with contrast for staging; PET-CT for distant metastases; plasma EBV DNA as tumor marker. For suspected colorectal carcinoma: colonoscopy with biopsy; CT chest/abdomen/pelvis for staging; CEA; microsatellite instability testing; germline testing for FAP (APC) and Lynch syndrome (MMR genes). For thyroid carcinoma: thyroid ultrasound; fine needle aspiration cytology (FNAC); thyroglobulin and calcitonin (for medullary thyroid carcinoma); germline RET testing in all pediatric MTC. All unusual pediatric malignancies should have tumor tissue submitted for comprehensive molecular profiling (next-generation sequencing, RNA fusion panel, methylation profiling for CNS tumors) — this may identify actionable mutations, confirm histological classification, and enable access to targeted therapy or clinical trials.

Treatment of unusual childhood cancers is highly individualized and type-specific. Adrenocortical carcinoma: complete surgical resection (adrenalectomy) is the primary treatment and only potential cure; incomplete resection or metastatic disease is treated with mitotane (adrenolytic agent) ± cisplatin-based chemotherapy (BEP or EDP protocol — etoposide, doxorubicin, cisplatin); outcome is poor for unresectable disease. Nasopharyngeal carcinoma in children/adolescents: concurrent cisplatin-based chemoradiation (IMRT to 70 Gy) following the same principles as adult NPC management (ASCO/NCCN guidelines); induction chemotherapy with TPF or GC before CRT is used for locally advanced disease; outcomes are generally more favorable than in adults. Pediatric colorectal adenocarcinoma: resection + FOLFOX or FOLFIRI chemotherapy; MSI-high tumors benefit from pembrolizumab immunotherapy. Pediatric papillary thyroid carcinoma: total thyroidectomy + radioactive iodine (RAI) I-131 ablation for metastatic disease; lifelong TSH suppression with levothyroxine; kinase inhibitors (lenvatinib) for RAI-refractory metastatic disease. Carcinoid tumors: appendiceal carcinoids ≤2 cm treated by appendectomy alone (curative); larger or metastatic carcinoids require somatostatin analogues (octreotide LAR, lanreotide), PRRT (peptide receptor radionuclide therapy), or surgery. Melanoma in children ≥12 years: BRAF V600E testing guides BRAF inhibitor + MEK inhibitor therapy (dabrafenib + trametinib); PD-1 inhibitors (pembrolizumab, nivolumab) are now approved for pediatric advanced melanoma. Enrollment in pediatric oncology clinical trials (COG, SIOPE) is strongly encouraged for all unusual childhood cancers.

The prognosis of unusual cancers of childhood varies enormously by tumor type, histology, stage, and molecular characteristics. Pediatric thyroid cancer — predominantly papillary thyroid carcinoma (PTC) — has an excellent prognosis despite frequent lymph node and pulmonary metastases; 10-year overall survival exceeds 90% with surgery and radioiodine, and even metastatic pediatric PTC usually responds to total thyroidectomy with RAI ablation. Pediatric adrenocortical carcinoma (ACC) carries a stage-dependent prognosis — stage I resected ACC has a 60–80% 5-year survival, while stage III–IV disease has a 5-year survival below 30%; mitotane-based adjuvant chemotherapy and germline TP53 testing (Li-Fraumeni syndrome) are key management elements. Pediatric nasopharyngeal carcinoma treated with platinum-based chemoradiation achieves 5-year overall survival of approximately 70–80%, comparable to adult NPC, reflecting the favorable EBV-driven biology of most pediatric NPC. Appendiceal carcinoid tumor — the most common childhood GI carcinoid — has a near-100% 5-year survival when the primary tumor is ≤2 cm and treated with appendectomy alone; larger tumors require right hemicolectomy. Pediatric melanoma has an improving prognosis with the advent of BRAF-targeted therapy (vemurafenib, dabrafenib) and anti-PD-1 immunotherapy (pembrolizumab), applicable to the 40–60% of pediatric melanomas that are BRAF V600E-mutant. Significant late effects from multimodal therapy — including endocrine dysfunction, growth disturbances, cardiac toxicity, neurocognitive impairment, and secondary malignancies — are important considerations in pediatric cancer survivorship planning. Enrollment in collaborative pediatric oncology group trials (COG, SIOPE) is essential given the rarity of these tumors.

Prevention of most unusual childhood cancers is not possible in sporadic cases. Genetic counseling and hereditary cancer syndrome testing is essential when clinical features, family history, or tumor characteristics suggest a predisposing genetic condition: Li-Fraumeni syndrome (TP53) testing for ACC, choroid plexus carcinoma, or any young child with cancer; FAP (APC) testing for colorectal adenoma/carcinoma in childhood or hepatoblastoma; Lynch syndrome (MMR genes) for colorectal carcinoma with MSI-high features in a child or adolescent; MEN2 (RET) testing and prophylactic thyroidectomy timing in RET mutation carriers — the timing depends on RET codon classification (highest-risk carriers undergo prophylactic thyroidectomy in infancy). EBV vaccination is not currently available but research is ongoing; avoidance of carcinogen exposure (tobacco, ionizing radiation) reduces risk. Long-term childhood cancer survivor programs address the substantial late effects of treatment — endocrine dysfunction, cardiac toxicity, secondary malignancies, neurocognitive impairment — through dedicated multidisciplinary survivor clinics. Annual follow-up is recommended indefinitely for survivors at elevated risk of secondary malignancies.

Parents should seek urgent medical evaluation if a child has: a persistently enlarging mass anywhere in the body (neck, abdomen, extremity) not explained by trauma or infection; persistent and progressive bone pain — particularly night pain — that wakes the child; unexplained and persistent weight loss, fatigue, or pallor; signs of virilization in a young girl (clitoral enlargement, pubic hair before age 8, acne, voice deepening); persistent nasal obstruction or hearing loss in one ear in an adolescent, particularly of East Asian origin; a thyroid nodule detected on examination; or a changing, asymmetric, large (>6 mm), or rapidly growing skin lesion, particularly in adolescents with a known giant congenital melanocytic nevus. Any child who previously received radiation therapy to any body site is at elevated risk of secondary malignancy in the radiation field and should receive regular surveillance imaging. For families with identified hereditary cancer syndromes, children should be enrolled in age-appropriate genetic surveillance programs at pediatric oncology centers experienced with hereditary cancer predisposition.