The tumor is rare, affecting adults in the 4th decade most commonly. Patients are usually younger than those who present with a lipoma. There is a slight male predominance. Hibernoma are most commonly identified in the subcutaneous and muscle tissue of the head and neck region (shoulders, neck, scapular), followed by thigh, back, chest, abdomen, and arms. In rare cases hibernoma may arise in bone tissue, however it is an incidental finding.

Lipomatosis is believed to be a hereditary condition in which multiple lipomas are present on the body.

Adiposis dolorosa (Dercum disease) is a rare condition involving multiple painful lipomas, swelling, and fatigue. Early studies mentioned prevalence in obese postmenopausal women. However, current literature demonstrates that Dercum disease is present in more women than men of all body types; the average age for diagnosis is 35 years.

Benign symmetric lipomatosis (Madelung disease) is another condition involving lipomatosis. It nearly always appears in middle-aged males after many years of alcoholism. But, non-alcoholics and females can also be affected.

The tendency to develop a lipoma is not necessarily hereditary, although hereditary conditions such as familial multiple lipomatosis might include lipoma development. Genetic studies in mice have shown a correlation between the "HMG I-C" gene (previously identified as a gene related to obesity) and lipoma development. These studies support prior epidemiologic data in humans showing a correlation between "HMG I-C" and mesenchymal tumors.

Cases have been reported where minor injuries are alleged to have triggered the growth of a lipoma, called "post-traumatic lipomas." However, the link between trauma and the development of lipomas is controversial.

Fibrosarcoma occurs most frequently in the mouth in dogs . The tumor is locally invasive, and often recurs following surgery . Radiation therapy and chemotherapy are also used in treatment. Fibrosarcoma is also a rare bone tumor in dogs.

In cats, fibrosarcoma occurs on the skin. It is also the most common vaccine-associated sarcoma. In 2014, Merial launched Oncept IL-2 in Europe for the management of such feline fibrosarcomas.

While cancer is generally considered a disease of old age, children can also develop cancer. In contrast to adults, carcinomas are exceptionally rare in children..

The two biggest risk factors for ovarian carcinoma are age and family history.

A 2006 review stated that RS often leads renal cancer between ages 30-50. Renal cancer kills about 1 in 3 people, but 5-year survival rates improved between 1974-1976 and 1995-2000, from 52% to 64%.

Sarcoma botryoides normally is found in children under 8 years of age. Onset of symptoms occurs at age 3 years (38.3 months) on average. Cases of older women with this condition have also been reported.

Hemangioendothelioma is used to describe a group of vascular neoplasms that may be considered benign as well as malignant, depending on the specific group member's activity.

Lipoblastoma is a type of subcutaneous benign fatty tumor.

Types include:

- Benign lipoblastomatosis, a tumor, also known as an embryonic lipoma, which usually occurs in children under three years old. This is the tumor of brown fat cells.

- Myxoid lipoblastoma, a cutaneous condition characterized by excess mucin

Mammary myofibroblastoma, abbreviated MMFB, (aka "Wargotz tumor") is a rare, benign tumor of the breast.

Surgery, with as wide a margin of removal as possible, has generally been the most effective and preferred way to attack LMS. If surgical margins are narrow or not clear of tumor, however, or in some situations where tumor cells were left behind, chemotherapy or radiation has been shown to give a clear survival benefit. While LMS tends to be resistant to radiation and chemotherapy, each case is different and results can vary widely.

LMS of uterine origin do frequently, but not always respond to hormonal treatments.

Complete surgical excision is the treatment of choice, associated with an excellent long term clinical outcome.

A gangliocytic paraganglioma, abbreviated GP, is a rare tumour that is typically found in the duodenum and consists of three components: (1) ganglion cells, (2) epithelioid cells (paraganglioma-like) and, (3) spindle cells (schwannoma-like).

Spitz nevi are uncommon. Their annual incidence was estimated in a coastal population of sub-tropical Queensland to be 1.4 cases per 100,000 people. For comparison, the annual incidence of melanoma in the same population, which is high by world standards is 25.4 cases per 100,000 people.

Although they are most commonly found on people in their first two decades of life, the age range for people with Spitz nevi is from 6 months to 71 years, with a mean age of 22 years and a median age of 19 years.

These tumors are painless masses that manifest as breast lumps and may be found on a mammogram.

Variants with edema can be associated with Meigs' syndrome. They may be a part of nevoid basal cell carcinoma syndrome (Gorlin syndrome).

Undifferentiated pleomorphic sarcoma is regarded as the most common soft tissue sarcoma of late adult life. It rarely occurs in children. It occurs more often in Caucasians than in those of African or Asian descent and is a male-predominant disease, afflicting two males for every female.

Leiomyosarcoma, also referred to as LMS, is a malignant (cancerous) smooth muscle tumor. A benign tumor originating from the same tissue is termed leiomyoma. It is also important to note that while it has been believed that leiomyosarcomas do not arise from leiomyomas, there are leiomyoma variants for which classification is evolving.

About 1 person in 100,000 gets diagnosed with LMS each year. Leiomyosarcoma is one of the more common types of soft-tissue sarcoma, representing 10 percent to 20 percent of new cases. (Leiomyosarcoma of the bone is more rare.) Sarcoma is rare, consisting of only 1 percent of cancer cases in adults. Leiomyosarcomas can be very unpredictable. They can remain dormant for long periods of time and recur after years. It is a resistant cancer, meaning generally not very responsive to chemotherapy or radiation. The best outcomes occur when it can be removed surgically with wide margins early, while small and still in situ.

A benign tumor is a mass of cells (tumor) that lacks the ability to invade neighboring tissue or metastasize. Benign tumors do not spread into, or invade, nearby tissues. Benign tumors can sometimes be quite large, however. When removed, they usually do not grow back, whereas malignant tumors sometimes do. Unlike most benign tumors elsewhere in the body, benign brain tumors can be life threatening. Benign tumors generally have a slower growth rate than malignant tumors and the tumor cells are usually more differentiated (cells have normal features). Benign tumors are typically surrounded by an outer surface (fibrous sheath of connective tissue) or remain with the epithelium. Common examples of benign tumors include moles and uterine fibroids.

Although benign tumors will not metastasize or locally invade tissues, some types may still produce negative health effects. The growth of benign tumors produces a "mass effect" that can compress tissues and may cause nerve damage, reduction of blood to an area of the body (ischaemia), tissue death (necrosis) and organ damage. The mass effect of tumors is more prominent if the tumor is within an enclosed space such as the cranium, respiratory tract, sinus or inside bones. Tumors of endocrine tissues may overproduce certain hormones, especially when the cells are well differentiated. Examples include thyroid adenomas and adrenocortical adenomas.

Although most benign tumors are not life-threatening, many types of benign tumors have the potential to become cancerous (malignant) through a process known as tumour progression. For this reason and other possible negative health effects, some benign tumors are removed by surgery.

PTEN hamartoma syndrome comprises four distinct hamartomatous disorders characterised by genetic mutations in the PTEN gene; Cowden syndrome, Bannayan-Riley-Ruvalcaba syndrome, Proteus syndrome and Proteus-like syndrome. Although they all have distinct clinical features, the formation of hamartomas is present in all four syndromes. PTEN is a tumor suppressor gene that is involved in cellular signalling. Absent or dysfunctional PTEN protein allows cells to over-proliferate, causing hamartomas.

Cowden syndrome is an autosomal dominant genetic disorder characterised by multiple benign hamartomas (trichilemmomas and mucocutaneous papillomatous papules) as well as a predisposition for cancers of multiple organs including the breast and thyroid. Bannayan-Riley-Ruvalcaba syndrome is a congenital disorder characterised by hamartomatous intestinal polyposis, macrocephaly, lipomatosis, hemangiomatosis and glans penis macules. Proteus syndrome is characterised by nevi, asymmetric overgrowth of various body parts, adipose tissue dysregulation, cystadenomas, adenomas, vascular malformation.

Individuals presenting with fibrosarcoma are usually adults aged thirty to fifty five years, often presenting with pain. In adults, males have a higher incidence for fibrosarcoma than females.

Mucinous tubular and spindle cell carcinoma (MTSCC) is a rare subtype of renal cell carcinoma (RCC), that is included in the 2004 WHO classification of RCC. MTSCC is a rare neoplasm and is considered as a low-grade entity. It may be a variant of papillary RCC. This tumor occurs throughout life (age range 17–82 years) and is more frequent in females.

Other relatively rare conditions have been reported in association with this disease. It is not yet known if these associations are fortuitous or manifestations of the condition itself.

Cerebral cavernomas and massive, macronodular adrenocortical disease have also been reported in association with this syndrome. A case of cutis verticis gyrata, disseminated collagenoma and Charcot-Marie-Tooth disease in association with a mutation in the fumarate hydratase gene has also been reported. Two cases of ovarian mucinous cystadenoma have also been reported with this mutation.

Spindle cell sarcoma is a type of connective tissue cancer in which the cells are spindle-shaped when examined under a microscope. The tumors generally begin in layers of connective tissue such as that under the skin, between muscles, and surrounding organs, and will generally start as a small lump with inflammation that grows. At first the lump will be self-contained as the tumor exists in its stage 1 state, and will not necessarily expand beyond its encapsulated form. However, it may develop cancerous processes that can only be detected through microscopic examination. As such, at this level the tumor is usually treated by excision that includes wide margins of healthy-looking tissue, followed by thorough biopsy and additional excision if necessary. The prognosis for a stage 1 tumor excision is usually fairly positive, but if the tumors progress to levels 2 and 3, prognosis is worse because tumor cells have likely spread to other locations. These locations can either be nearby tissues or system-wide locations that include the lungs, kidneys, and liver. In these cases prognosis is grim and chemotherapy and radiation are the only methods of controlling the cancer.

Spindle cell sarcoma can develop for a variety of reasons, including genetic predisposition but it also may be caused by a combination of other factors including injury and inflammation in patients that are already thought to be predisposed to such tumors. Spindle cells are a naturally occurring part of the body's response to injury. In response to an injury, infection, or other immune response the connective tissues will begin dividing to heal the affected area, and if the tissue is predisposed to spindle cell cancer the high cellular turnover may result in a few becoming cancerous and forming a tumor.

Prognosis depends on the primary tumor grade (appearance under the microscope as judged by a pathologist), size, resectability (whether it can be completely removed surgically), and presence of metastases. The five-year survival is 80%.