Ewing's sarcoma is more common in males (1.6 male:1 female) and usually presents in childhood or early adulthood, with a peak between 10 and 20 years of age. It can occur anywhere in the body, but most commonly in the pelvis and proximal long tubular bones, especially around the growth plates. The diaphyses of the femur are the most common sites, followed by the tibia and the humerus. Thirty percent are overtly metastatic at presentation. Patients usually experience extreme bone pain.

Signs and symptoms include: intermittent fevers, anemia, leukocytosis, increased sedimentation rate, and other symptoms of inflammatory systemic illness. Also, depending on the type, progression, and location of the tumor, great pain may occur.

According to the Bone Cancer Research Trust (BCRT), the most common symptoms are: localized pain, swelling, and sporadic bone pain with variable intensity. The swelling is most likely to be visible if the sarcoma is located on a bone near the surface of the body, but when it occurs in other places deeper in the body, like on the pelvis, it may not be visible.

Ewing sarcoma or Ewing's sarcoma () is a malignant small, round, blue cell tumor. It is a rare disease in which cancer cells are found in the bone or in soft tissue. The most common areas in which it occurs are the pelvis, the femur, the humerus, the ribs and clavicle (collar bone).

Since a common genetic locus is responsible for a large percentage of Ewing sarcoma and primitive neuroectodermal tumors, these are sometimes grouped together in a category known as the Ewing family of tumors.

Ewing sarcoma occurs most frequently in teenagers and young adults, with a male/female ratio of 1.6:1.

Although usually classified as a bone tumor, Ewing's sarcoma can have characteristics of both mesodermal and ectodermal origin, making it difficult to classify.

James Ewing (1866–1943) first described the tumour, establishing that the disease was separate from lymphoma and other types of cancer known at that time.

Many patients first complain of pain that may be worse at night, may be intermittent and of varying intensity and may have been occurring for some time. Teenagers who are active in sports often complain of pain in the lower femur, or immediately below the knee. If the tumor is large, it can present as overt localised swelling. Sometimes a sudden fracture is the first symptom, because affected bone is not as strong as normal bone and may fracture abnormally with minor trauma. In cases of more deep-seated tumors that are not as close to the skin, such as those originating in the pelvis, localised swelling may not be apparent.

An osteosarcoma (OS) or osteogenic sarcoma (OGS) is a cancerous tumor in a bone. Specifically, it is an aggressive malignant neoplasm that arises from primitive transformed cells of mesenchymal origin (and thus a sarcoma) and that exhibits osteoblastic differentiation and produces malignant osteoid.

Osteosarcoma is the most common histological form of primary bone cancer. It is most prevalent in teenagers and young adults.

A sarcoma is a cancer that arises from transformed cells of mesenchymal origin. Thus, malignant tumors made of cancellous bone, cartilage, fat, muscle, vascular, or hematopoietic tissues are, by definition, considered sarcomas. This is in contrast to a malignant tumor originating from epithelial cells, which are termed carcinoma. Human sarcomas are quite rare. Common malignancies, such as breast, colon, and lung cancer, are almost always carcinoma. The term is from the Greek "sarx" meaning "flesh".

Dogs with limb osteosarcoma typically show lameness and swelling at the affected site. For other sites, dogs may show difficulty to open their mouth (if jaw bone cancer), nasal discharge (if nasal cavity bone cancer) or neurological signs (if spine bone cancer).

Sarcomas are given a number of different names based on the type of tissue that they most closely resemble. For example, osteosarcoma resembles bone, chondrosarcoma resembles cartilage, liposarcoma resembles fat, and leiomyosarcoma resembles smooth muscle.

A transmissible cancer is a cancer cell or cluster of cancer cells that can be transferred between individuals without the involvement of an infectious agent, such as an oncovirus. Transmission of cancer between humans is rare.

Contagious cancers occur in dogs, Tasmanian devils, Syrian hamsters, and some marine bivalves including soft-shell clams. These cancers have a relatively stable genome as they are transmitted.

In humans, a significant fraction of Kaposi's sarcoma occurring after transplantation may be due to tumorous outgrowth of donor cells. Although Kaposi's sarcoma is caused by a virus (Kaposi's sarcoma-associated herpesvirus), in these cases, it appears likely that transmission of virus-infected tumor cells—rather than the free virus—caused tumors in the transplant recipients.

In male dogs, the tumor affects the penis and foreskin. In female dogs, it affects the vulva. Rarely, the mouth or nose are affected. The tumor often has a cauliflower-like appearance. Signs of genital TVT include a discharge from the prepuce and in some cases urinary retention, from blockage of the urethra. Signs of a nasal TVT include nasal fistulae, nosebleeds and other nasal discharge, facial swelling, and enlargement of the submandibular lymph nodes.

The most common bone tumor is called osteosarcoma, and typically affects middle-age to older dogs of large and giant breeds. Osteosarcoma is less common in cats. Osteosarcoma is an aggressive cancer that can develop in any bone of the body but the majority is seen in the limbs (e.g. long bones such as radius, humerus, femur, and tibia).

Symptoms of cancer in dogs may include:

- Lumps (which are not always malignant, but should always be examined by a vet)

- Swelling

- Persistent sores

- Abnormal discharge from any part of the body

- Bad breath

- Listlessness/lethargy

- Rapid, often unexplained weight loss

- Sudden lameness

- Offensive odor

- Black, tarry stools (a symptom of ulcers, which can be caused by mast cell tumors)

- Decreased or loss of appetite

- Difficulty breathing, urinating or defecating

Patients usually present with pain and limited range of motion caused by tumor's proximity to the joint space. Swelling may occur, as well, if the tumor has been growing for a long time. Some patients may be asymptomatic until they develop a pathologic fracture at the site of the tumor. They usually originate from the epiphysis of long bones, but in rare cases, they may arise from anterior arc of the ribs.

The symptoms may include muscular aches and pains in arms or legs and abdominal pain. Patients may also experience nerve pain which feels like an electric shock due to weight bearing.

Giant-cell tumor of the bone (GCTOB) is a relatively uncommon tumor of the bone. It is characterized by the presence of multinucleated giant cells (osteoclast-like cells). Malignancy in giant-cell tumor is uncommon and occurs in about 2% of all cases. However, if malignant degeneration does occur, it is likely to metastasize to the lungs. Giant-cell tumors are normally benign, with unpredictable behavior. It is a heterogeneous tumor composed of three different cell populations. The giant-cell tumour stromal cells (GCTSC) constitute the neoplastic cells, which are from an osteoblastic origin and are classified based on expression of osteoblast cell markers such as alkaline phosphatase and osteocalcin. In contrast, the mononuclear histiocytic cells (MNHC) and multinucleated giant cell (MNGC) fractions are secondarily recruited and comprise the non-neoplastic cell population. They are derived from an osteoclast-monocyte lineage determined primarily by expression of "CD68", a marker for monocytic precursor cells. In most patients, the tumors are slow to develop, but may recur locally in as many as 50% of cases.

Canine transmissible venereal tumors (CTVTs), also called transmissible venereal tumors (TVTs), canine transmissible venereal sarcoma (CTVS), sticker tumors and infectious sarcoma is a histiocytic tumor of the external genitalia of the dog and other canines, and is transmitted from animal to animal during mating. It is one of only three known transmissible cancers in mammals; other are devil facial tumor disease, a cancer which occurs in Tasmanian devils, and contagious reticulum cell sarcoma of the Syrian hamster.

The tumor cells are themselves the infectious agents, and the tumors that form are not genetically related to the host dog. Although the genome of a CTVT is derived from a canid (probably a dog, wolf or coyote), it is now essentially living as a unicellular, asexually reproducing (but sexually transmitted) pathogen. Sequence analysis of the genome suggests it diverged from canids over 6,000 years ago; possibly much earlier. The most recent estimates of its time of origin place date it to about 11,000 years ago. However, the most recent common ancestor of "extant" tumors is more recent: it probably originated 200 to 2,500 years ago.

Canine TVTs were initially described by Russian veterinarian M.A. Novinsky (1841–1914) in 1876, when he demonstrated that the tumor could be transplanted from one dog to another by infecting them with tumor cells.

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)

Patients with osteoblastoma usually present with pain of several months' duration. In contrast to the pain associated with osteoid osteoma, the pain of osteoblastoma usually is less intense, usually not worse at night, and not relieved readily with salicylates (aspirin and related compounds). If the lesion is superficial, the patient may have localized swelling and tenderness. Spinal lesions can cause painful scoliosis, although this is less common with osteoblastoma than with osteoid osteoma. In addition, lesions may mechanically interfere with the spinal cord or nerve roots, producing neurologic deficits. Pain and general weakness are common complaints.

Osteoblastoma is an uncommon osteoid tissue-forming primary neoplasm of the bone.

It has clinical and histologic manifestations similar to those of osteoid osteoma; therefore, some consider the two tumors to be variants of the same disease, with osteoblastoma representing a giant osteoid osteoma. However, an aggressive type of osteoblastoma has been recognized, making the relationship less clear.

Although similar to osteoid osteoma, it is larger (between 2 and 6 cm).

In humans, eosinophilic granulomas are considered a benign histiocytosis that occurs mainly in adolescents and young adults. Clinically, unifocal lytic lesions are found in bones such as the skull, ribs and femur. Because of this, bone pain and pathologic fractures are common.

Cancer is the leading cause of death in dogs. It is estimated that 1 in 3 domestic dogs will develop cancer, which is the same incidence of cancer among men. Dogs can develop a variety of cancers and most are very similar to those found in humans. Dogs can develop carcinomas of epithelial cells and organs, sarcomas of connective tissues and bones, and lymphomas or leukemias of the circulatory system. Selective breeding of dogs has led certain pure-bred breeds to be at high-risk for specific kinds of cancer.

Veterinary oncology is the medical study of cancer in animals, and can be diagnosed and treated by specialized veterinarians called veterinary oncologists.

DFTD tumours are "large, solid, soft tissue masses usually with flattened, centrally ulcerated, and surfaces", which are "typically multicentric, appearing first in the oral, face, or neck regions", and are " to nodular aggregates of round to spindle-shaped cells, often within a pseudocapsule and divided into lobules by delicate fibrous septae". The disease is described as being aggressive, locally. Tumours can cover the eyes.

As Iain O'Neill notes, it also presents a "high rate of regional lymph node involvement and systemic metastasis"; of the avenues by which the cancer can spread systemically, metastasis to the lungs, spleen, and heart are observed, as is secondary "intracranial involvement". O'Neill also notes that "organ involvement and superimposed infection may... contribute to mortality." Moreover, growth of large tumours impedes feeding, and starvation is another cause of death in affected devils.

Because different parts of the brain are responsible for different functions, symptoms vary depending on the site of metastasis within the brain. However, brain metastases should be considered in any cancer patient who presents with neurological or behavioral changes.

Brain metastases can cause a wide variety of symptoms which can also be present in minor, more common conditions. Neurological symptoms are often caused by increased intracranial pressure, with severe cases resulting in coma. The most common neurological symptoms include:

- New onset headaches: headaches occur in roughly half of brain metastasis patients, especially in those with many tumors.

- Paresthesias: patients often present with (hemiparesis), or weakness on only one side of the body, which is often a result of damage to neighboring brain tissue.

- Ataxia: when metastasis occurs to the cerebellum, patients will experience various difficulties with spatial awareness and coordination.

- Seizures: when present, often indicates disease involvement of the cerebral cortex.

Animals that have undergone population bottlenecks may be at greater risks of contracting transmissible cancers. Because of their transmission, it was initially thought that these diseases were caused by the transfer of oncoviruses, in the manner of cervical cancer caused by HPV.

- Canine transmissible venereal tumor (CTVT) is sexually transmitted cancer in dogs. It was experimentally transplanted between dogs in 1876 by M. A. Novinsky (1841–1914). A single malignant clone of CTVT cells has colonized dogs worldwide, representing the oldest known malignant cell line in continuous propagation.

- Contagious reticulum cell sarcoma of the Syrian hamster can be transmitted from one Syrian hamster to another by means of the bite of the mosquito "Aedes aegypti".

- Devil facial tumour disease (DFTD) is a transmissible parasitic cancer in the Tasmanian devil.

- Soft-shell clams, "Mya arenaria", have been found to be vulnerable to a transmissible neoplasm of the hemolymphatic system — effectively, leukemia.

- Horizontally transmitted cancers have also been discovered in three other species of marine bivalves: bay mussels ("Mytilus trossulus"), common cockles ("Cerastoderma edule") and golden carpet shell clams ("Polititapes aureus"). The golden carpet shell clam cancer was found to have been transmitted from another species, the pullet carpet shell ("Venerupis corrugata").

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.

Cats with eosinophilic granuloma complex (EGC) may have one or more of four patterns of skin disease.

The most frequent form is "eosinophilic plaque". This is a rash comprising raised red to salmon-colored and flat-topped, moist bumps scattered on the skin surface. The most common location is on the ventral abdomen and inner thigh.

Another form of EGC is the "lip ulcer". This is a painless, shallow ulcer with raised and thickened edges that forms on the upper lip adjacent to the upper canine tooth. It is often found on both sides of the upper lips.

The third form of the EGC is the "collagenolytic granuloma". This is a firm swelling that may be ulcerated. The lesions may form on the skin, especially of the face, in the mouth, or on the feet, or may form linear flat-topped raised hairless lesions on the back of the hind legs, also called "linear granuloma".

The least common form of EGC is "atypical eosinophilic dermatitis". It is unique in that it is caused by mosquito bite allergy and the lesions form on the parts of the body with the least hair affording easy access to feeding mosquitoes. This includes the bridge of the nose, the outer tips of the ears and the skin around the pads of the feet. The lesions are red bumps, shallow ulcers and crusts.

The most common sources of brain metastases in a case series of 2,700 patients undergoing treatment at the Memorial Sloan–Kettering Cancer Center were:

- Lung cancer, 48%

- Breast cancer, 15%

- Genitourinary tract cancers, 11%

- Osteosarcoma, 10%

- Melanoma, 9%

- Head and neck cancer, 6%

- Neuroblastoma, 5%

- Gastrointestinal cancers, especially colorectal and pancreatic carcinoma, 3%

- Lymphoma, 1%

Lung cancer and melanoma are most likely to present with multiple metastasis, whereas breast, colon, and renal cancers are more likely to present with a single metastasis.