Table 8. Characteristics of Melanocytic Lesions continued...
Most BCCs have activation of the hedgehog pathway, generally resulting from mutations in PTCH1. Vismodegib (GDC-0449), a hedgehog pathway inhibitor, has been approved for the treatment of adult patients with BCC.[128,129] It was approved by the U.S. Food and Drug Administration for the treatment of adults with metastatic BCC or with locally advanced BCC that has recurred following surgery or who are not candidates for surgery, and who are not candidates for radiation. This drug also reduces the tumor burden in patients with basal cell nevus syndrome.
(Refer to the PDQ summary on adult Skin Cancer Treatment for more information.)
Chordoma is a very rare tumor of bone that arises from remnants of the notochord within the clivus, spinal vertebrae, or sacrum. The incidence in the United States is approximately one case per one million people per year, and only 5% of all chordomas occur in patients younger than 20 years. Most pediatric patients have the conventional or chondroid variant of chordoma.[131,132]
Younger children appear to have a worse outlook than older patients.[131,133,134,135,136] The survival rate in children and adolescents ranges from about 50% to 80%.[131,134,136]
Patients usually present with pain, with or without neurologic deficits such as cranial or other nerve impairment. Diagnosis is straightforward when the typical physaliferous (soap-bubble-bearing) cells are present. Differential diagnosis is sometimes difficult and includes dedifferentiated chordoma and chondrosarcoma. Childhood chordoma has been associated with tuberous sclerosis complex.
Standard treatment includes surgery and external radiation therapy, often proton-beam radiation. Surgery is not commonly curative in children and adolescents because of difficulty obtaining clear margins and the likelihood of the chordoma arising in the skull base, rather than in the sacrum, making them relatively inaccessible to complete surgical excision. The best results have been obtained using proton-beam therapy (charged-particle radiation therapy).[138,139]; [136,140][Level of evidence: 3iiA]; [Level of evidence: 3iiiDiii]
There is no known effective cytotoxic agent or combination chemotherapy for this disease, with only anecdotal reports published. Imatinib mesylate has been studied in adults with chordoma on the basis of the overexpression of PDGFR alpha, beta, and KIT in this disease.[142,143] Among 50 adults with chordoma treated with imatinib and evaluable by RECIST, there was one partial response and 28 additional patients had stable disease at 6 months. The low rate of RECIST responses and the potentially slow natural course of the disease complicate the assessment of the efficacy of imatinib for chordoma. Other tyrosine kinase inhibitors and combinations involving kinase inhibitors have been studied.[144,145,146]