Myosarcoma is a malignant muscle tumor. People with myosarcoma often wake up with the feeling as if they had a cramp during their sleep.

Leiomyosarcoma is sarcoma of smooth muscle, and rhabdomyosarcoma is sarcoma of striated muscle. However, the term myosarcoma itself still appears in the literature.

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.

Smooth muscle cells make up the involuntary muscles, which are found in most parts of the body, including the uterus, stomach and intestines, the walls of all blood vessels, and the skin. It is therefore possible for leiomyosarcomas to appear at any site in the body. They are most commonly found in the uterus, stomach, small intestine and retroperitoneum.

Uterine leiomyosarcomas come from the smooth muscle in the muscle layer of the uterus. Cutaneous leiomyosarcomas derive from the pilo-erector muscles in the skin. Gastrointestinal leiomyosarcomas might come from smooth muscle in the GI tract or, alternatively, also from a blood vessel. At most other primary sites—retroperitoneal extremity (in the abdomen, behind the intestines), truncal, abdominal organs, etc.—leiomyosarcomas appear to grow from the muscle layer of a blood vessel (the tunica media). Thus a leiomyosarcoma can have a primary site of origin anywhere in the body where there is a blood vessel.

The tumors are usually hemorrhagic and soft and microscopically marked by pleomorphism, abundant (15–30 per 10 high power fields) abnormal mitotic figures, and coagulative tumor cell necrosis. There is a wide differential diagnosis, which includes spindle cell carcinoma, spindle cell melanoma, fibrosarcoma, malignant peripheral nerve sheath tumor and even biphenotypic sinonasal sarcoma.

Smooth muscle tumours show a smooth muscle differentiation. There are two main types of smooth muscle tumour: the benign leiomyoma and the malignant leiomyosarcoma.

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.

Medulloepithelioma is a rare, primitive, fast-growing brain tumour thought to stem from cells of the embryonic medullary cavity. Tumours originating in the ciliary body of the eye are referred to as embryonal medulloepitheliomas, or diktyomas.

A highly malignant undifferentiated primitive neuroepithelial tumour of children, medulloepithelioma may contain bone, cartilage, skeletal muscle, and tends to metastasize extracranially.

Medulloepithelioma most commonly affect children between 6 months and 5 years; rarely, this tumour may occur congenitally or beyond this age range. Incidence is equal in males and females.

PECs bear significant histologic and immunohistochemical similarity to:

- angiomyolipoma,

- clear-cell sugar tumour (CCST),

- lymphangioleiomyomatosis, and,

- clear-cell myomelanocytic tumour of ligamentum teres/falciform ligament.

- abdominopelvic sarcoma of perivascular epitheloid cells

- primary extrapulmonary sugar tumour

Thus, it has been advocated that the above could be classified PEComas.

PEComas are rare and can have myriad features; therefore, they can be confused with carcinomas, smooth muscle tumours, adipocytic tumours, clear cell sarcomas, melanomas and gastrointestinal stromal tumours (GIST).

A leiomyoma, also known as fibroids, is a benign smooth muscle tumor that very rarely becomes cancer (0.1%). They can occur in any organ, but the most common forms occur in the uterus, small bowel, and the esophagus. Polycythemia may occur due to increased erythropoietin production as part of a paraneoplastic syndrome.

The word is from "" + "" + "", "smooth-muscle tumor".

The symptoms may be similar to those classically associated with renal cell carcinoma, and may include polycythemia, abdominal pain, hematuria and a palpable mass. Mean age at onset is around 40 years with a range of 5 to 83 years and the mean size of the tumour is 5.5 cm with a range 0.3 to 15 cm (1). Polycythemia is more frequent in MA than in any other type of renal tumour. Of further relevance is that this tumour is more commonly calcified than any other kidney neoplasm. Surgery is curative and no other treatment is recommended. There is so far no evidence of metastases or local recurrence.

APAs are characterized by glands with abnormal shapes that: (1) often have squamous metaplasia, and (2) are surrounded by benign smooth muscle. Nuclear atypia, if present, is mild.

The microscopic differential diagnosis includes endometrial carcinoma and endocervical adenocarcinoma.

Smooth muscle tumor of uncertain malignant potential, abbreviated STUMP, is an uncommon tumor of the uterine smooth muscle that may behave like a benign tumor or a cancerous tumor.

This tumor should not be confused with the prostatic stromal tumor of uncertain malignant potential which may be abbreviated the same way ("STUMP").

The Bell criteria were developed to help categorize them and differentiate them from their main differential diagnoses, leiomyosarcoma and uterine leiomyoma.

Uterine fibroids are leiomyomata of the uterine smooth muscle. As other leiomyomata, they are benign, but may lead to excessive menstrual bleeding (menorrhagia), often cause anemia and may lead to infertility.

A rare form of these tumors is uterine lipoleiomyoma—benign tumors consisting of a mixture of adipocytes and smooth muscle cells. Uterine lipoleiomyomata have been observed together with ovarian and other pathologies and some of them may develop into liposarcoma. These tumors are monoclonal, and non-random chromosomal abnormalities have been seen in 40% of the tumors.

In their early stages, soft-tissue sarcomas usually do not cause symptoms. Because soft tissue is relatively elastic, tumors can grow rather large, pushing aside normal tissue, before they are felt or cause any problems. The first noticeable symptom is usually a painless lump or swelling. As the tumor grows, it may cause other symptoms, such as pain or soreness, as it presses against nearby nerves and muscles. If in the abdomen it can cause abdominal pains commonly mistaken for menstrual cramps, indigestion, or cause constipation.

"Benign" serous tumours are unilocular (have one lobe); however if very large may be multilocular, contain clear fluid and have a smooth lining composed of columnar epithelial cells with cilia. On gross examination, the serous tumor may present as either a cystic lesion in which the papillary epithelium is contained within a few fibrous walled cysts, or the papillary projections may be away from the surface epithelium. Surgery is curative.

Spermatocytic seminoma is a rare tumour, making up only one to two percent of all testicular germ cell tumours. Men presenting with this tumour are generally 50 to 60 years old, and its occurrence is rare in men under 30 years old. Most present with slow, painless testicular enlargement, which may involve both testes.

JCT is morphologically characterized by multiple foci malignant mesenchymal epithelioid cells with, often with admixed necrosis, and a perivascular growth pattern. The immunophenotype is rather characteristic, as the neoplastic cells express renin, CD34, smooth muscle actin, CD138, vimentin, collagen IV and is negative for cytokeratins as well as for S100, c-Kit and desmin.

Spermatocytic seminoma is a neoplasm of the testis ("i.e." a tumour of the testis), and classified as a germ cell tumour.

The name of the tumour comes from the similarity (under the microscope) between the small cells of the tumour and secondary spermatocytes.

Metanephric adenoma (MA)is a rare, benign tumour of the kidney, that can have a microscopic appearance similar to a nephroblastoma (Wilms tumours), or a papillary renal cell carcinoma.

It should not be confused with the pathologically unrelated, yet similar sounding, "mesonephric adenoma".

By hypersecretion of renin, JCT causes hypertension, often severe and usually sustained but occasionally paroxysmal, and secondary hyperaldosteronism inducing hypokalemia, though the later can be mild despite high renin. Both of these conditions may be corrected by surgical removal of the tumor. Asymptomatic cases have been reported.

There are many subtypes of lipomas:

- Adenolipomas are lipomas associated with eccrine sweat glands.

- Angiolipoleiomyomas are acquired, solitary, asymptomatic nodules, characterized histologically by well-circumscribed subcutaneous tumors composed of smooth muscle cells, blood vessels, connective tissue, and fat.

- Angiolipomas are painful subcutaneous nodules having all other features of a typical lipoma.

- Cerebellar pontine angle and internal auditory canal lipomas

- Chondroid lipomas are deep-seated, firm, yellow tumors that characteristically occur on the legs of women.

- Corpus callosum lipoma is a rare congenital brain condition that may or may not present with symptoms. This occurs in the corpus callosum, also known as the calossal commissure, which is a wide, flat bundle of neural fibers beneath the cortex in the human brain.

- Hibernomas are lipomas of brown fat.

- Intradermal spindle cell lipomas are distinct in that they most commonly affect women and have a wide distribution, occurring with relatively equal frequency on the head and neck, trunk, and upper and lower extremities.

- Neural fibrolipomas are overgrowths of fibro-fatty tissue along a nerve trunk, which often leads to nerve compression.

- Pleomorphic lipomas, like spindle-cell lipomas, occur for the most part on the backs and necks of elderly men and are characterized by floret giant cells with overlapping nuclei.

- Spindle-cell lipomas are asymptomatic, slow-growing subcutaneous tumors that have a predilection for the posterior back, neck, and shoulders of older men.

- Superficial subcutaneous lipomas, the most common type of lipoma, lie just below the surface of the skin. Most occur on the trunk, thigh, and forearm, although they may be found anywhere in the body where fat is located.

Serous tumours are part of the surface epithelial-stromal tumour group of ovarian neoplasms, which derive from Mullerian epithelium.

They are common neoplasms with a strong tendency to bilaterality, and they account for 50% of all ovarian tumours.

Sixty percent are benign (cystadenoma), 10% are borderline and 30% are malignant (cystadenocarcinoma).

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.

Ancillary testing for fibrosarcoma includes IHC, where vimentin is positive, cytokeratin and S100 are negative, and actin is variable.

IPMs present as painless lymphadenopathy. They usually are found in the inguinal region and grow slowly.

The signs and symptoms are non-specific, i.e. it is not possible to diagnose an IPM from the symptoms and manner in which they present.

The main (clinical) differential diagnosis of IPM is metastatic cancer, e.g. squamous cell carcinoma, malignant melanoma, adenocarcinoma.