Congenital mesoblastic nephroma typically (76% of cases) presents as an abdominal mass which is detected prenatally (16% of cases) by ultrasound or by clinical inspection (84% of cases) either at birth or by 3.8 years of age (median age ~1 month). The neoplasm shows a slight male preference. Concurrent findings include hypertension (19% of cases), polyhydramnios (i.e. excess of amniotic fluid in the amniotic sac) (15%), hematuria (11%), hypercalcemia (4%), and elevated serum levels of the kidney-secreted, hypertension-inducing enzyme, renin (1%). Congenital anomalies have been reported in 11 patients: 6 with genitourinary anomalies, 2 with gastrointestinal anomalies, 1 with hydrocephalus, and 1 with the Beckwith–Wiedemann syndrome. The vast majority of patients present with localized (i.e. non-metastatic) disease. Most patients' disease is classified at presentation as stage I or II (i.e. localized), few patients present with stage III (i.e. locally advanced/infiltrating), and virtually no patients present with stage IV (metastases present or V (i.e. tumors in both kidneys) disease (see staging of renal cancer).

Diagnosis of mesoblastic nephroma and its particular type (i.e. classic, mixed, or cellular) is made by histological examination of tissues obtained at surgery. Besides its histological appearance, various features of this disease aid in making a differential diagnosis that distinguish it from the following childhood neoplasms:

- Wilm's tumor is the most common childhood kidney neoplasm, representing some 85% of cases. Unlike mesoblastic nephroma, 3 years of age. Bilateral kidney tumors, concurrent birth defects, and/or metastatic disease at presentation favor a diagnosis of Wilm's tumor.

- congenital infantile sarcoma is a rare aggressive sarcoma typically presenting in the lower extremities, head, or neck of infants during their first year of life. The histology, association with the "ETV6-NRTK3" fusion gene along with certain chromosome trisomies, and the distribution of markers for cell type (i.e. cyclin D1 and Beta-catenin) within this tumor are the same as those found in cellular mesoblastic nephroma. Mesoblastic nephroma and congenital infantile sarcoma appear to be the same diseases with mesoblastic lymphoma originating in the kidney and congenital infantile sarcoma originating in non-renal tissues.

- Rhabdoid tumor, which accounts for 5-510% of childhood kidney neoplasms, occurs predominantly in children from 1 to 2 years of age. Unlike mesoblastic nephroma, rhabdoid tumors may present with tumors in other tissues including in ~13% of cases, the brain. Rhabdoid tumors have a distinctive histology and abnormalities (i.e. loss of heterozygosity, single nucleotide polymorphism, and deletions) in chromosome 22.

- Clear cell sarcoma of the kidney, which is responsible for 5-10% of childhood pediatric tumors, occurs predominantly in children from 2 to 3 years of age. Unlike meoblastic nephorma, clear cell sarcoma of the kidney presents with metastasis, particularly to bone, in 5-6% of cases; it histology is diverse and has been mistaken for mesoblastic nephroma. One chromosomal translocations t,(10;17)(q22;p13), has been repeatedly reported to be associated with clear cell sarcoma of the kidney.

- Infantile myofibromatosis is a fibrous tumor of infancy and childhood most commonly presenting during the first 2 years of life as a single subcutaneous nodule of the head and neck region or less commonly as multiple lesions of skin, muscle, bone, and in ~33% of these latter cases, visceral organs. All of these lesions have an excellent prognosis and can regress spontaneously except for those in which there is visceral involvement where the prognosis is poor. While infantile myofibromatosis and classic mesoblastic nephroma have been suggested to be the same diseases because of their very similar histology, studies on the distribution of cell-type markers (i.e. cyclin D1 and Beta-catenin) indicate that they have different cellular origins.

Pineoblastoma (also pinealoblastoma) is a malignant tumor of the pineal gland. A pineoblastoma is a supratentorial midline primitive neuroectodermal tumor.

Pineoblastoma may occur in patients with hereditary uni- or bilateral retinoblastoma. When retinoblastoma patients present with pineoblastoma this is characterized as "trilateral retinoblastoma". Up to 5% of patients with hereditary retinoblastoma are at risk of developing trilateral retinoblastoma. Prognosis of patients with trilateral retinoblastoma is dismal, only a few patients have survived more than 5 years after diagnosis; all survivors were diagnosed with small tumors in a subclinical stage. Recent advances in (high-dose) chemotherapy treatment regimens and early detection have improved survival of patients with trilateral retinoblastoma to up to 50%.

Childhood rhabdomyosarcoma consists of three subgroups. Embryonal is the most common among children and young adults. Alveolar and anaplastic rhabdomyosarcoma occur in the teenage years.

- Embryonal rhabdomyosarcoma develops within the first seven weeks of the embryo's development. Rapid cell growth causes masses to form along the head, neck, urinary tract, and genital organs.

- Alveolar, the second most common group, is seen later in life. During the teen years, large muscle groups come under attack, including the torso and large appendages. Aggressive treatment is needed to stop or limit progression of alveolar rhabdomyosarcoma.

- Anaplastic rhabdomyosarcoma is rarely seen in children and only precise intensive lab work can identify it.

Childhood rhabdomyosarcoma is difficult to diagnose. Factors that increase the likelihood of this cancer include Li-Fraumeni syndrome, type one Neurofibromatosis, Beckwith-Wiedemann syndrome, Costello syndrome, and Noonan syndrome. Each contribute to deformations of bones, tissue, and muscles.

Trilateral retinoblastoma (TRb) is a malignant midline primitive neuroectodermal tumor occurring in patients with inherited uni- or bilateral retinoblastoma. In most cases trilateral retinoblastoma presents itself as pineoblastoma (pineal TRb). In about a fourth of the cases the tumor develops in another intracranial region, most commonly supra- or parasellar (non-pineal TRb), but there are reported cases with non-pineal TRb in the 3rd ventricle. In most cases pineal TRb is diagnosed before the age of 5, but after the diagnosis of retinoblastoma. Non-pineal TRb, however, is often diagnosed simultaneous with retinoblastoma. Prognosis of patients with trilateral retinoblastoma is dismal, only a few patients have survived more than 5 years after diagnosis; all survivors were diagnosed with small tumors in a subclinical stage. Recent advances in (high-dose) chemotherapy treatment regimens and early detection have improved survival of patients with trilateral retinoblastoma.

The most common and obvious sign of retinoblastoma is an abnormal appearance of the retina as viewed through the pupil, the medical term for which is leukocoria, also known as amaurotic cat's eye reflex. Other signs and symptoms include deterioration of vision, a red and irritated eye with glaucoma, and faltering growth or delayed development. Some children with retinoblastoma can develop a squint, commonly referred to as "cross-eyed" or "wall-eyed" (strabismus). Retinoblastoma presents with advanced disease in developing countries and eye enlargement is a common finding.

Depending on the position of the tumors, they may be visible during a simple eye exam using an ophthalmoscope to look through the pupil. A positive diagnosis is usually made only with an examination under anesthetic (). A white eye reflection is not always a positive indication of retinoblastoma and can be caused by light being reflected badly or by other conditions such as Coats' disease.

The presence of the photographic fault red eye in only one eye and not in the other may be a sign of retinoblastoma. A clearer sign is "white eye" or "cat's eye" (leukocoria).

There are two forms of the disease, a heritable form and non-heritable form (all cancers are considered genetic in that mutations of the genome are required for their development, but this does not imply that they are heritable, or transmitted to offspring). Approximately 55% of children with retinoblastoma have the non-heritable form. If there is no history of the disease within the family, the disease is labeled "sporadic", but this does not necessarily indicate that it is the non-heritable form. Bilateral retinoblastomas are commonly heritable, while unilateral retinoblastomas are commonly non-heritable.

In about two-thirds of cases, only one eye is affected (unilateral retinoblastoma); in the other third, tumors develop in both eyes (bilateral retinoblastoma). The number and size of tumours on each eye may vary. In certain cases, the pineal gland or the suprasellar or parasellar region (or in very rare cases other midline intracranial locations) is also affected (trilateral retinoblastoma). The position, size and quantity of tumours are considered when choosing the type of treatment for the disease.

The most common cancers in children are (childhood) leukemia (32%), brain tumors (18%), and lymphomas (11%). In 2005, 4.1 of every 100,000 young people under 20 years of age in the U.S. were diagnosed with leukemia, and 0.8 per 100,000 died from it. The number of new cases was highest among the 1–4 age group, but the number of deaths was highest among the 10–14 age group.

In 2005, 2.9 of every 100,000 people 0–19 years of age were found to have cancer of the brain or central nervous system, and 0.7 per 100,000 died from it. These cancers were found most often in children between 1 and 4 years of age, but the most deaths occurred among those aged 5–9. The main subtypes of brain and central nervous system tumors in children are: astrocytoma, brain stem glioma, craniopharyngioma, desmoplastic infantile ganglioglioma, ependymoma, high-grade glioma, medulloblastoma and atypical teratoid rhabdoid tumor.

Other, less common childhood cancer types are:

- Neuroblastoma (6%, nervous system)

- Wilms tumor (5%, kidney)

- Non-Hodgkin lymphoma (4%, blood)

- Childhood rhabdomyosarcoma (3%, many sites)

- Retinoblastoma (3%, eye)

- Osteosarcoma (3%, bone cancer)

- Ewing sarcoma (1%, many sites)

- Germ cell tumors (5%, many sites)

- Pleuropulmonary blastoma (lung or pleural cavity)

- Hepatoblastoma and hepatocellular carcinoma (liver cancer)

In a case series of 34 patients, Davis and colleagues reported the following signs and symptoms:

- macroscopically visible (gross) hematuria (60%)

- abdominal or back/flank pain (50%)

- significant weight loss (25%)

Other researchers have reported a palpable renal mass or enlarged lymph nodes.

Renal medullary carcinoma is a rare type of cancer that affects the kidney. It tends to be aggressive, difficult to treat, and is often metastatic at the time of diagnosis. Most individuals with this type of cancer have sickle cell trait or rarely sickle cell disease, suggesting that the sickle cell trait may be a risk factor for this type of cancer.

Childhood cancer (also known as pediatric cancer) is cancer in a child. In the United States, an arbitrarily adopted standard of the ages used are 0–14 years inclusive, that is, up to 14 years 11.9 months of age. However, the definition of childhood cancer sometimes includes adolescents between 15–19 years old. Pediatric oncology is the branch of medicine concerned with the diagnosis and treatment of cancer in children.

Worldwide, it is estimated that childhood cancer has an incidence of more than 175,000 per year, and a mortality rate of approximately 96,000 per year. In developed countries, childhood cancer has a mortality of approximately 20% of cases. In low resource settings, on the other hand, mortality is approximately 80%, or even 90% in the world's poorest countries. In many developed countries the incidence is slowly increasing, as rates of childhood cancer increased by 0.6% per year between 1975 and 2002 in the United States and by 1.1% per year between 1978 and 1997 in Europe.

Prognosis varies widely depending on severity of symptoms, degree of intellectual impairment, and associated complications. Because the syndrome is rare and so newly identified, there are no long term studies.

Physical Symptoms

- Heart Defects

- Characteristics of Autism

- Genital defects (in males)

- Childhood hypotonia

- Respiratory infections

- Motor Delay

- Renal defects

Behavioural Symptoms

- Passiveness

- Sociability

- Aggression

- Biting, and/or hitting

- Moodiness

- Disliking routine changes

Diagnosis is usually based on clinical observation. Various sets of criteria have been suggested to identify the disorder in an individual patient, all of which include macrocephaly and a number of the following: somatic overgrowth, cutis marmorata, midline facial birthmark, polydactyly/syndactyly, asymmetry (hemihyperplasia or hemihypertrophy), hypotonia at birth, developmental delay, connective tissue defect and frontal bossing. Currently no consensus exists about which diagnostic criteria are definitive and so evaluation by a medical geneticist or other clinician with familiarity with the syndrome is usually needed to provide diagnostic certainty. It is not clear if there are some features which are mandatory to make the diagnosis, but macrocephaly appears essentially universal though may not be congenital. The distinctive vascular abnormalities of the skin often fade over time, making the diagnosis challenging in older children with this condition.

The brain can be affected in several ways in this syndrome. Some children are born with structural brain anomalies such as cortical dysplasia or polymicrogyria. While developmental delay is nearly universal in this syndrome it is variable in severity, with the majority having mild to moderate delays and a minority having severe cognitive impairment. Some patients are affected with a seizure disorder. White matter abnormalities on magnetic resonance imaging (MRI), suggesting a delay in white matter myelination, is commonly seen in early childhood. Some patients may have asymmetry of the brain, with one side being noticeably larger than the other.

One interesting phenomenon that seems very common in this syndrome is the tendency for disproportionate brain growth in the first few years of life, with crossing of percentiles on the head circumference growth charts. A consequence of this disproportionate brain growth appears to be a significantly increased risk of cerebellar tonsillar herniation (descent of the cerebellar tonsils through the foramen magnum of the skull, resembling a Chiari I malformation neuroradiologically) and ventriculomegaly/hydrocephalus. Such cerebellar tonsil herniation may occur in up to 70% of children with M-CM.

The medical literature suggests that there is a risk of cardiac arrhythmias in early childhood. The cause for this is unknown. In addition, a variety of different congenital cardiac malformations have been reported in a small number of patients with this disorder.

Like other syndromes associated with disproportionate growth, there appears to be a slightly increased risk of certain types of childhood malignancies in M-CM (such as Wilms' tumor). However, the precise incidence of these malignancies is unclear.

Xanthoma disseminatum (also known as "Disseminated xanthosiderohistiocytosis" and "Montgomery syndrome") is a rare cutaneous condition that preferentially affects males in childhood, characterized by the insidious onset of small, yellow-red to brown papules and nodules that are discrete and disseminated.

It is a histiocytosis syndrome.

9q34 deletion syndrome, also known as Kleefstra syndrome, is a rare genetic disorder. Terminal deletions of chromosome 9q34 have been associated with childhood hypotonia, a distinctive facial appearance and developmental disability. The facial features typically described include arched eyebrows, small head circumference, midface hypoplasia, prominent jaw and a pouting lower lip. Individuals with this disease may often have speech impediments, such as speech delays. Other characteristics of this disease include: epilepsy, congenital and urogenetic defects, microcephaly, corpulence, and psychiatric disorders. From analysis of chromosomal breakpoints, as well as gene sequencing in suggestive cases, Kleefstra and colleagues identified EHMT1 as the causative gene.

This gene is responsible for producing the protein Histone methyltransferase which functions to alter histones. Ultimately, histone methyltransferases are important in deactivating certain genes, needed for proper growth and development. Moreover, a frameshift, missense, or nonsense error in the coding sequence of EHMT1 can result in this condition in an individual.

Most initial symptoms of leukemia are similar to symptoms for irregular bone-marrow function. Typically, most symptoms do not occur during the early stages of leukemia, and children may experience different symptoms. The following are symptoms of leukemia that lead doctors to look for different types of juvenile leukemia:

Certain treatments for childhood cancer are known to cause learning problems in survivors, particularly when central nervous system (CNS)-directed therapies are used (e.g. radiation; high-dose methotrexate or cytarabine; or intrathecal chemotherapy). As the mortality rates of childhood cancers have plummeted since effective treatment regiments have been introduced, greater attention has been paid to the effect of treatment on neurocognitive morbidity and quality of life of survivors. The goal of treatment for childhood cancers today is to minimize these adverse "late effects", while ensuring long-term survival.

Vulvar childhood pemphigoid is a cutaneous condition, a childhood form of bullous pemphigoid, peculiar variant with involvement of the genital area and perineum.

This syndrome is characterised by typical facial appearance, slight build, thin and translucent skin, severely adducted thumbs, arachnodactyly, club feet, joint instability, facial clefting and bleeding disorders, as well as heart, kidney or intestinal defects. Severe psychomotor and developmental delay and decreased muscle tone may also be present during infancy. Cognitive development during childhood is normal.

Refractory cytopenia of childhood (RCC) is a subgroup of myelodysplastic syndrome (MDS), having been added to the World Health Organization classification in 2008. Before then, RCC cases were classified as childhood aplastic anemia. RCC is the most common form of MDS in children and adolescents, accounting for approximately half of all MDS cases.

This syndrome is associated with microcephaly, arthrogryposis and cleft palate and various craniofacial, respiratory, neurological and limb abnormalities, including bone and joint defects of the upper limbs, adducted thumbs, camptodactyly and talipes equinovarus or calcaneovalgus. It is characterized by craniosynostosis, and myopathy in association with congenital generalized hypertrichosis.

Patients with the disease are considered intellectually disabled. Most die in childhood. Patients often suffer from respiratory difficulties such as pneumonia, and from seizures due to dysmyelination in the brain's white matter. It has been hypothesized that the Moro reflex (startle reflex in infants) may be a tool in detecting the congenital clapsed thumb early in infancy. The thumb normally extends as a result of this reflex.

Leukemia is diagnosed in a variety of ways. Some diagnostic procedures include:

- A bone-marrow aspiration and biopsy; marrow may be removed by aspiration or a needle biopsy.

- A complete blood count, which is a measurement of size, number, and maturity of different blood cells in blood.

- Blood tests may include blood chemistry, evaluation of liver and kidney functions, and genetic studies.

- A lymph-node biopsy; lymph node tissue is surgically removed to examine under a microscope, to look for cancerous cells.

- A spinal tap: a special needle is placed into the lower back into the spinal canal, which is the area around the spinal cord. Cerebral spinal fluid is fluid that bathes the child's brain and spinal cord. A small amount of cerebral spinal fluid is sent for testing to determine if leukemia cells are present.

Hereditary sclerosing poikiloderma is an autosomal dominant conditions with skin changes consisting of generalized poikiloderma appearing in childhood.