When the tumor is large and there is presence of necrosis and local recurrence, the prognosis is poor. Presence of metastasis occurs in more than 50% cases and the common places of its occurrence are the bone, lymph node and lungs. Five-year survival rates, which are reported to be between 50-65%, can be misleading because the disease is prone to late metastasis or recurrence. Ten and twenty-year survival rates are 33% and 10%, respectively.

Perivascular epithelioid cell tumour, also known as PEComa or PEC tumour, is a family of mesenchymal tumours consisting of perivascular epithelioid cells (PECs). These are rare tumours that can occur in any part of the human body.

The cell type from which these tumours originate remains unknown. Normally, no perivascular epitheloid cells exist; the name refers to the characteristics of the tumour when examined under the microscope.

Establishing the malignant potential of these tumours remains challenging although criteria have been suggested; some PEComas display malignant features whereas others can cautiously be labeled as having 'uncertain malignant potential'. The most common tumours in the PEComa family are renal angiomyolipoma and pulmonary lymphangioleiomyomatosis, both of which are more common in patients with tuberous sclerosis complex. The genes responsible for this multi-system genetic disease have also been implicated in other PEComas.

Many PEComa types shows a female predominance in the sex ratio.

Clear-cell sarcoma (formerly known as malignant melanoma of the soft parts) is a rare form of cancer called sarcoma. It is known to occur mainly in the soft tissues and dermis. Rare forms were thought to occur in the gastrointestinal tract before they were discovered to be different and redesignated as GNET.

Recurrence is common.

It has been associated with both EWSR1-ATF1 and EWSR1-CREB1 fusion transcripts.

Clear cell sarcoma of the soft tissues in adults is not related to the pediatric tumor known as clear cell sarcoma of the kidney.

The precursor cell of PEComas is currently unknown; there is no normal counterpart "perivascular epitheloid cell". Genetically, PECs are linked to the tuberous sclerosis genes TSC1 and TSC2, although this link is stronger for angiomyolipoma and lymphangioleiomyomatosis than for other members of the PEComa family.

Epithelioid sarcoma is a rare soft tissue sarcoma arising from Mesenchyme tissue and characterized by epithelioid-like features. It accounts for less than 1% of all soft tissue sarcomas. It was first clearly characterized by F.M. Enzinger in 1970. It commonly presents itself in the distal limbs (fingers, hands, forearms, or feet) of young adults as a small, soft mass or a series of bumps. A proximal version has also been described, frequently occurring in the upper extremities. Rare cases have been reported in the pelvis, vulva, penis, and spine.

Histologically, epithelioid sarcoma forms nodules with central necrosis surrounded by bland, polygonal cells with eosinophilic cytoplasm and peripheral spindling. Epithelioid sarcomas typically express vimentin, cytokeratins, epithelial membrane antigen, and CD34, whereas they are usually negative for S100, desmin, and FLI-1. They typically stain positive for CA125.

Epithelioid sarcoma most commonly strikes young adults, yet no age group is immune. The disease has a tendency to develop local recurrences and metastasis thereafter to regional lymph nodes, lung, bone, brain, and other locations, including the scalp. Generally speaking, epithelioid sarcoma has a high rate of relapse after initial treatment and tends to recur locally (at or near the original tumor site). Epithelioid sarcoma also demonstrates lymphatic spread (in 22-48% of cases), and metastasis (in 21-63% of cases). These events, as well as advanced stage (progression) and grade (aggressiveness), are predictive of an overall worse outcome. The overall five-year survival rate for epithelioid sarcoma is anywhere from 25 to 78%. Importantly, the 10-year and 15-year survival rate drops off significantly. Associated with a more positive outcome are younger age, female vs. male sex, distal vs. proximal location, smaller tumor size, and negative margins upon tumor resection.

The 5-year survival rate for epithelioid sarcoma patients is 50-70%, and the 10-year survival rate is 42-55%. Children with epithelioid sarcoma tend to have slightly better outcomes than adults, with 5 year survival rates around 65%. Pediatric patients also tend to display less lymphatic spread and metastasis. In addition to stage and grade of the tumor, gender, site, age at diagnosis, tumor size and microscopic pathology have all been shown to affect prognosis. Advanced stage and grade are associated with worse outcomes. Females tend to have more favorable outcomes than males, proximal cases show worse outcomes than distal cases, and younger age is associated with more positive outcomes. Tumors more than 2 cm in diameter and tumors with necrosis and vascular invasion have been correlated with a worse outcome.

The gold standard for chemotherapy is a combination of doxorubicin and ifosfamide. However, recent studies have suggested that the addition of ifosfamide to doxorubicin does not necessarily lead to an increase in overall survival. Etoposide, vincristine, dactinomycin, and cyclophosphamide have also traditionally been given. Newer chemotherapies, such as gemcitabine and pazopanib, are currently being tested in clinical trials.

Radiation therapy is also a treatment option when tumors are deemed inoperable or wide surgical margins are not achievable. Radiation therapy in combination with chemotherapy has so far resulted in only minimal improvements to response rates. Trials with brachytherapy (an internal radiation treatment that delivers a high dose of radiation directly to the tumor and is thought to have fewer long-term side effects) have produced some positive results.

The treatment of choice for both benign and malignant SFT is complete "en bloc" surgical resection.

Prognosis in benign SFTs is excellent. About 8% will recur after first resection, with the recurrence usually cured after additional surgery.

The prognosis in malignant SFTs is much more guarded. Approximately 63% of patients will have a recurrence of their tumor, of which more than half will succumb to disease progression within 2 years. Adjuvant chemotherapy and/or radiotherapy in malignant SFT remains controversial.

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).

10-year survival rates for mucinous tumors is excellent in the absence of invasion.

In the case of borderline tumors confined to the ovary and malignant tumors without invasion, the survival rates are 90% or greater. In invasive mucinous cystadenocarcinomas, the survival is approximately 30%

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.

Surgical excision is the preferred method of treatment for benign glomus tumors.

Recurrent somatic fusions of the two genes, NGFI-A–binding protein 2 (NAB2) and STAT6, located at chromosomal region 12q13, have been identified in solitary fibrous tumors.

A splenic tumor is a rare form of tumor that may be malignant or benign. Malignant forms include lymphoma and sarcoma.

Lymphoma is the most common malignant splenic tumor.

Hidradenocarcinoma (also known as malignant hidradenoma, malignant acrospiroma, clear cell eccrine carcinoma, or primary mucoepidermoid cutaneous carcinoma) is a malignant adnexal tumor of the sweat gland. It is the malignant variant of the benign hidradenoma. It may develop de novo or in association with an existent hidradenoma.

This type of tumor typically develops in older individuals (after age 40).

The most common presentation is gastrointestinal bleed (~45% of cases), followed by abdominal pain (~43% of cases) and anemia (~15% of cases).

JCT often is described as benign, however one case of metastasis has been reported, so its malignant potential is uncertain. In most cases the tumor is encapsulated.

The most common adverse effect is pain, which is usually associated with solitary lesions. Multiple tumors are less likely to be painful.

In one report, a patient with more than 400 glomus tumors had thrombocytopenia as a result of platelet sequestration (i.e. Kasabach-Merritt syndrome).

Malignant glomus tumors, or glomangiosarcomas, are extremely rare and usually represent a locally infiltrative malignancy. However, metastases do occur and are usually fatal.

Treatment is varied and depends on the site and extent of tumor involvement, site(s) of metastasis, and specific individual factors. Surgical resection, radiotherapy, and chemotherapy have all been used to treat these masses, although studies on survival have yet to be conducted to delineate various treatment regimens.

Malignant triton tumor (MTT) is a relatively rare, aggressive tumor made up of both malignant schwannoma cells and malignant rhabdomyoblasts. It's classified as a malignant peripheral nerve sheath tumor with rhabdomyosarcomatous differentiation.

The unusual name "triton" was first used in reference to observation of supernumerary limbs containing bone and muscle growing on the backs of triton salamanders after the implantation of sciatic nerve tissue.

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.

Prostatic stromal tumour of uncertain malignant potential, abbreviated PSTUMP, is a rare tumour of the prostate gland stroma that may behave benign or like cancer, i.e. "malignant".

It can be abbreviated STUMP; an abbreviation used for a uterine lesion of uncertain malignant potential.

It is also known as prostatic stromal proliferation of uncertain malignant potential (abbreviated PSPUMP).

A thymoma is a tumor originating from the epithelial cells of the thymus that may be benign or malignant. Thymomas are frequently associated with the neuromuscular disorder myasthenia gravis; thymoma is found in 20% of patients with myasthenia gravis. Once diagnosed, thymomas may be removed surgically. In the rare case of a malignant tumor, chemotherapy may be used.

Malignant meningioma is a rare, fast-growing tumor that forms in one of the inner layers of the meninges (thin layers of tissue that cover and protect the brain and spinal cord). Malignant meningioma often spreads to other areas of the body.

The World Health Organization classification system defines both grade II and grade III meningiomas as malignant. Historically, histological subtypes have also been used in classification including:

- clear cell (WHO grade II),

- chordoid (WHO grade II),

- rhabdoid (WHO grade III), and

- papillary (WHO grade III)

Benign or low grade meningiomas (WHO grade I) include meningothelial, fibrous, transitional, psammomatous, angiomatous, microcystic, secretory, lymphoplasmacyte-rich, and metaplastic.

Focal nodular hyperplasia (FNH) is a benign tumor of the liver (hepatic tumor), which is the second most prevalent tumor of the liver (the first is hepatic hemangioma). It is usually asymptomatic, rarely grows or bleeds, and has no malignant potential. This tumour was once often resected because it was difficult to distinguish from hepatic adenoma, but with modern multiphase imaging is usually now diagnosed by strict imaging criteria and not resected.

Men and women are equally affected by thymomas. The typical age at diagnosis is 30–40, although cases have been described in every age group, including children.