Other rare childhood cancers include skin cancer, clear cell sarcoma of tendon sheaths, and cancer of unknown primary site. These other rare childhood cancers are discussed below.

Multiple endocrine neoplasia (abnormal and uncontrolled cell growth) syndromes are familial disorders that include cancerous changes in more than one endocrine organ at the same time (endocrine tissue secretes hormones). These changes may include hyperplasia (overgrowth of tissue) or benign (noncancerous) tumors. The distinct involvement of multiple glandular structures are referred to as MEN-1 (Werner’s syndrome) which may involve tumors of the pituitary gland and parathyroid, adrenal, gastric, and pancreatic structures. MEN-2a (Sipple syndrome) is associated with medullary thyroid carcinoma, parathyroid hyperplasia, and adenomas as well as pheochromocytoma; MEN-2b is associated with medullary thyroid carcinoma, parathyroid hyperplasia, and adenomas as well as pheochromocytoma, mucosal neuromas, and ganglioneuromas. An additional complex is referred to as the Carney complex, which is associated with heart and skin tumors.

Patients with the MEN-2b syndrome may have a slender body build, long and thin extremities, a high arch palate, and “funnel chest” (sunken chest) or an abnormally high arch in the foot. The lips may appear thickened because of tumors in the mucous membranes. In this syndrome, medullary thyroid cancer may be particularly aggressive; therefore, the thyroid should be removed by age 5 or 6 years in affected individuals.

The outcome for patients with the MEN-1 syndrome is generally good, provided adequate treatment can be obtained for parathyroid, pancreatic, and pituitary tumors. The outcome for patients with the MEN-2a syndrome is also generally good, but the possibility exists for recurrence of medullary thyroid carcinoma and pheochromocytoma. Medullary thyroid cancer in children with MEN-2b may be difficult to cure. For patients with the Carney complex, prognosis depends on how often heart and skin tumors recur.

Melanoma is thought to be the most common skin cancer in children, followed by basal cell and squamous cell carcinomas. The incidence of melanoma in children and adolescents represents approximately 1% of the new cases of melanoma that are diagnosed annually in the United States. In all instances, melanoma in the pediatric population is similar to that of adults in relation to site of presentation, symptoms, description, spread, and prognosis,

The most common cause of skin cancer of any type is exposure to the ultraviolet (UV) portion of sunlight. Other causes may be related to chemical carcinogenesis, radiation exposure, immunodeficiency, or immunosuppression. The person who is most likely to develop a melanoma is easily sunburned, has poor tanning ability, and generally has light hair, blue eyes, and pale skin. Worldwide, there is an increasing incidence of both melanoma and nonmelanoma skin cancers. Melanoma presents as a relatively flat, dark-colored lesion that may enlarge, penetrate the skin, or metastasize.

Melanomas may be congenital (present at birth). They are sometimes associated with large congenital black spots known as melanocytic nevi, which may cover the trunk and thigh. Children with hereditary immunodeficiencies have an increased lifetime risk of developing melanoma.

Individuals with atypical moles, which include raised lesions (that may or may not bleed) and various color hues (brown, tan, pink, black) are at an increased risk of having melanoma and having children affected by these premalignant lesions. Basal cell carcinoma generally appears as a raised lump or ulcerated lesion, usually in areas with previous sun exposure. Squamous cell carcinomas are usually reddened lesions with varying degrees of scaling or crusting; they have an appearance similar to eczema, infections, trauma, or psoriasis.

Basal and squamous cell carcinomas are generally curable with surgery alone, but the treatment of melanoma requires greater consideration because of its potential for metastasis. Surgery for melanoma depends on the size, site, level of invasion, and metastatic extent or stage of the tumor.

Chordoma is a very rare type of bone tumor that may develop along the spine at any point from the base of the skull to the tailbone. Chordomas start in clusters of cells leftover from spinal column development in the embryo. These cells normally disappear, but very rarely they remain and grow into tumors. In children and adolescents, especially girls, chordomas often develop in the clivus, a bone at the base of the skull. Symptoms vary and may include pain and nerve trouble. When chordoma recurs, it usually comes back in the same area, but may appear in the lungs or other areas of bone.

Standard treatment includes surgery and radiation therapy. The best results are seen with proton beam therapy, a special kind of high-energy radiation that is different from an x-ray.

Cancer can form in any tissue of the body and can spread from the primary site (the place where the cancer first began to grow) to other parts of the body. Cancer that has spread from the place in which it started to other parts of the body is called metastatic cancer. Metastatic cancer cells usually look like cells in the type of tissue where the cancer began. For example, breast cancer cells that spread to the lung look like breast cancer cells, not lung cancer cells. Sometimes metastatic cancer cells are found in the body, but tests do not find a primary tumor. If cancer cells are found in the body but the place where the cancer started cannot be identified, the disease is called cancer of unknown primary site. Treatment is based on what the cancer cells look like under a microscope, the patient's symptoms, and the extent of the cancer in the body. Treatment is usually chemotherapy or radiation therapy.