Vascular tissue neoplasms, like neoplasms of all tissues, are classified to benign and malignant ones, according to their biological behavior.

A vascular tissue neoplasm is a tumor arising from endothelial cells, the cells that line the wall of blood vessels and lymphatic vessels, as well as the heart. Vascular tissue neoplasms is a group containing tumors with the same tissue origin; in other words, it denotes histological classification, rather than anatomic (i.e. where in the body the neoplasm is found) or clinical one. They can occur everywhere in the body where vessels are to be found.

A myxoid liposarcoma is a malignant adipose tissue neoplasm of myxoid appearance histologically.

Myxoid liposarcomas are the second most common type of liposarcoma, representing 30–40% of all liposarcomas in the limbs; occurring most commonly in the legs, particularly the thigh, followed by the buttocks, retroperitoneum, trunk, ankle, proximal limb girdle, head and neck, and wrist. They occur in the intermuscular fascial planes or deep-seated areas. They present as a large, slow-growing, painless mass.

They are associated with a fusion between DDIT3 or "CHOP" (at 12q13.1-q13.2) and FUS or "TLS" (at 16p11.2) or EWS (at 22q12.2).

The specific translocation of FUS-DDIT3 is t(12;16)(q13;p11).

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.

One general danger of hamartomas is that they may impinge into blood vessels, resulting in a risk of serious bleeding. Because a hamartoma typically lacks elastic tissue, it may lead to the formation of aneurysms and thus possible hemorrhage. Where a hamartoma impinges into a major blood vessel, such as the renal artery, hemorrhage must be considered life-threatening.

Angiomyolipoma of the kidney was previously considered to be a hamartoma or choristoma.

Hamartomas of the spleen are uncommon but can be dangerous. About 50% of such cases manifest abdominal pain, and they are often associated with hematologic abnormalities and spontaneous rupture.

Hemangioendotheliomas may be classified as:

- "Epithelioid sarcoma-like hemangioendothelioma" is an exceedingly rare vascular tumor of intermediate grade that was first described by Steven Billings, Andrew Folpe, and Sharon Weiss in 2003. These tumors are so named because their histologic appearance is very similar to that of epithelioid sarcoma, a more malignant tumor with which they are commonly mistaken.

- "Composite hemangioendothelioma" is a low-grade angiosarcoma typically occurring in adults, although it has been described in infancy.

- "Spindle-cell hemangioendothelioma") is a vascular tumor that was first described in 1986 by Sharon Weiss, M.D., and commonly presents in a child or young adult who develops blue nodules of firm consistency on a distal extremity. These tumors were reclassified by Dr. Weiss in 1996 as "spindle cell hemangioma", rather than hemangioendothelioma, due to the excellent prognosis observed in a group of 78 patients.

- "Retiform hemangioendothelioma" (also known as a "Hobnail hemangioendothelioma") is a low-grade angiosarcoma, first described in 1994, presenting as a slow-growing exophytic mass, dermal plaque, or subcutaneous nodule.

- "Kaposiform hemangioendothelioma" (also known as "Infantile kaposiform hemangioendothelioma") is an uncommon vascular tumor, first described by Niedt, Greco, et al. (Hemangioma with Kaposi's sarcoma-like features: report of two cases.(Niedt GW, Greco MA, Wieczorek R, Blanc WA, Knowles DM 2nd. that affects infants and young children, with rare cases having also been reported in adults.Pediatr Pathol. 1989;9(5):567-75.)

- "Endovascular papillary angioendothelioma", also known as "Dabska tumor", "papillary intralymphatic angioendothelioma" (PILA), "Dabska-type hemangioendothelioma", "hobnail hemangioendothelioma", and "malignant endovascular papillary angioendothelioma", is a rare low-grade angiosarcoma of lymphatic channels. Approximately 30 such tumors have been described in the medical literature. Although included in the World Health Organization tumor classification, there is uncertainty as to whether EPA is a distinct entity or a heterogenous group of tumours. The lesion usually presents as a slow-growing tumor of the skin and subcutaneous tissues of the head, neck, or extremity, of infants or young children. However, EPA has involved the testicle, deep muscle tissue as a neoplastic transformation of a larger existing benign cavernous hemangioma, bone and spleen, and has been found in adults. Some reports indicate a good prognosis but metastasis is occasionally seen.

- "Infantile hemangioendothelioma" is a rare benign vascular tumour arising from mesenchymal tissue and is usually located in the liver. It often presents in infancy with cardiac failure because of extensive arteriovenous shunting within the lesion. It is the third most common liver tumor in children, the most common benign vascular tumor of the liver in infancy, and the most common symptomatic liver tumor during the first 6 months of life. These hemangioendotheliomas have 2 growth phases: an initial rapid growth phase, which is followed by a period of spontaneous involution (usually within the first 12 to 18 months of life). Detection of the hemangioendothelioma within the first 6 months of life is attributed to the initial rapid growth during this time; however, the tumor has been detected with fetal ultrasonography. Histopathologically, there are 2 types of hepatic hemangioendotheliomas:

- Type I: Hemagioendotheliomas of this type have multiple vascular channels that are formed by an immature endothelial lining with stromal separation from bile ductules.

- Type II: These hemangioendotheliomas have an appearance that is more disorganized and hypercellular, and there are no bile ductules.

A neoplasm can be benign, potentially malignant, or malignant (cancer).

- Benign tumors include uterine fibroids and melanocytic nevi (skin moles). They are circumscribed and localized and do not transform into cancer.

- Potentially-malignant neoplasms include carcinoma in situ. They are localised, do not invade and destroy but in time, may transform into a cancer.

- Malignant neoplasms are commonly called cancer. They invade and destroy the surrounding tissue, may form metastases and, if untreated or unresponsive to treatment, will prove fatal.

- Secondary neoplasm refers to any of a class of cancerous tumor that is either a metastatic offshoot of a primary tumor, or an apparently unrelated tumor that increases in frequency following certain cancer treatments such as chemotherapy or radiotherapy.

- Rarely there can be a metastatic neoplasm with no known site of the primary cancer and this is classed as a cancer of unknown primary origin

Considered part of the PTEN hamartoma tumor syndrome (PHTS), which also includes Bannayan-Riley-Ruvalcaba syndrome, Proteus syndrome, and Proteus-like syndrome, Cowden syndrome is a serious genetic disorder characterized by multiple hamartomas. Usually skin hamartomas exist, and commonly (in about 66% of cases) hamartoma of the thyroid gland exists. Additional growths can form in many parts of the body, especially in bones, CNS, the eyes, the genitourinary tract, the GI tract, and mucosa. The hamartomas themselves may cause symptoms or even death, but morbidity is more often associated with increased occurrence of malignancies, usually in the breast or thyroid.

Pain is the most common symptom, followed by either sensorineural or conductive hearing loss, tinnitus or drainage (discharge). A mass lesion may be present, but it is often slow growing.

This tumor only affects the outer 1/3 to 1/2 of the external auditory canal as a primary site. If this area is not involved, the diagnosis should be questioned. The most common tumor type is ceruminous adenoid cystic carcinoma and ceruminous adenocarcinoma, NOS.

Neoplasm is an abnormal growth of tissue which, if it forms a mass, is commonly referred to as a tumor. This abnormal growth (neoplasia) usually but not always forms a mass.

ICD-10 classifies neoplasms into four main groups: benign neoplasms, in situ neoplasms, malignant neoplasms, and neoplasms of uncertain or unknown behavior. Malignant neoplasms are also simply known as cancers and are the focus of oncology.

Prior to the abnormal growth of tissue, as neoplasia, cells often undergo an abnormal pattern of growth, such as metaplasia or dysplasia. However, metaplasia or dysplasia does not always progress to neoplasia. The word is from Ancient Greek νέος- "neo" "new" and πλάσμα "plasma" "formation, creation".

Focal nodular hyperplasia's most recognizable gross feature is a central stellate scar seen in 60–70% of cases. Microscopically, a lobular proliferation of bland-appearing hepatocytes with a bile ductular proliferation and malformed vessels within the fibrous scar is the most common pattern. Other patterns include telangiectatic, hyperplastic-adenomatous, and lesions with focal large-cell dysplasia. Rarely, these lesions may be multiple or can occur as part of a syndrome with hemangiomas, epithelioid hemangioendothelioma, hepatic adenomas, fibrolamellar hepatocellular carcinoma, vascular malformations of the brain, meningiomas, and/or astrocytomas.

Patients typically present with swelling with or without pain. The slow-growing tumor predominantly arises in long bones in a subcortical location (95% in the tibia or fibula). Most commonly, patients are in their second or third decade, but adamantinoma can occur over a wide age range.

Benign osteofibrous dysplasia may be a precursor of adamantinoma or a regressive phase of adamantinoma.

Histologically, islands of epithelial cells are found in a fibrous stroma. The tumor is typically well-demarcated, osteolytic and eccentric, with cystic zones resembling soap bubbles.

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.

The treatment is simple excision and exclusion of a malignant neoplasm.

This lesion has been called a fetal lipoma, lipoma of embryonic fat or a lipoma of immature fat.

Adamantinoma (from the Greek word "adamantinos", meaning "very hard") is a rare bone cancer, making up less than 1% of all bone cancers. It almost always occurs in the bones of the lower leg and involves both epithelial and osteofibrous tissue.

The condition was first described by Fischer in 1913.

Children affected by pilocytic astrocytoma can present with different symptoms that might include failure to thrive (lack of appropriate weight gain/ weight loss), headache, nausea, vomiting, irritability, torticollis (tilt neck or wry neck) difficulty to coordinate movements and visual complaints (including nystagmus). The complaints may vary depending on the location and size of the neoplasm. The most common symptoms are associated with increased intracranial pressure due to the size of the neoplasm.

Sebaceous lymphadenoma is a tissue diagnosis, e.g. salivary gland biopsy.

It may be confused with a number of benign and malignant neoplasms, including Warthin tumour, mucoepidermoid carcinoma and sebaceous lymphadenocarcinoma.

Patients present with a slow-growing, painless, solitary mass, usually of the subcutaneous tissues. It is much less frequently noted in the intramuscular tissue. It is not uncommon for symptoms to be present for years.

Benign neoplasm with "BROWN FAT" is noted.

Solid pseudopapillary tumours are typically round, well-demarcated, measuring 2–17 cm in diameter (average 8 cm), with solid and cystic areas with hemorrhage on cut sections.

A connective tissue neoplasm or connective tissue tumor is a neoplasm arising from the tissues of the connective tissue. (Not all tumors "in" the connective tissue are "of" the connective tissue.)

Fibrillary astrocytomas also called low grade or diffuse astrocytomas, are a group of primary slow growing brain tumors. They typically occur in adults between the ages of twenty and fifty.

Pancreatic serous cystadenoma, also known as serous cystadenoma of the pancreas and serous microcystic adenoma, a benign tumour of pancreas. It is usually found in the head of the pancreas, and may be associated with von Hippel-Lindau syndrome.

In contrast to some of the other cyst-forming tumors of the pancreas (such as the intraductal papillary mucinous neoplasm and the mucinous cystic neoplasm), serous cystic neoplasms are almost always entirely benign. There are some exceptions; rare case reports have described isolated malignant serous cystadenocarcinomas. In addition, serous cystic neoplasms slowly grow, and if they grow large enough they can press on adjacent organs and cause symptoms.

Pilocytic astrocytoma or juvenile pilocytic astrocytoma or cystic cerebellar astrocytoma (and its variant juvenile pilomyxoid astrocytoma) is a brain tumor that occurs more often in children and young adults (in the first 20 years of life). They usually arise in the cerebellum, near the brainstem, in the hypothalamic region, or the optic chiasm, but they may occur in any area where astrocytes are present, including the cerebral hemispheres and the spinal cord. These tumors are usually slow growing and benign. The neoplasms are associated with the formation of a single (or multiple) cyst(s), and can become very large.

Pilocytic astrocytomas are often cystic, and, if solid, tend to be well-circumscribed. It is characteristically easily seen on Computed tomography (CT scans) and Magnetic Resonance Imaging (MRI).

Juvenile pilocytic astrocytoma is associated with neurofibromatosis type 1 (NF1), and optic gliomas are among the most frequently encountered tumors in patients with this disorder. The majority of pilocytic astrocytomas have a unique KIAA1549-BRAF fusion gene.