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.

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

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.

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.

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).

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

RMS can occur in almost any soft-tissue site in the body; the most common primary sites are genitourinary (24%), parameningeal (16%), extremity (19%), orbit (9%), other head and neck (10%), and miscellaneous other sites (22%). RMS often presents as a mass, but signs and symptoms can vary widely depending on the site of the primary tumor. Genitourinary tumors may present with hematuria, urinary tract obstruction, and/or a scrotal or vaginal mass. Tumors that arise in the retroperitoneum and mediastinum can become quite large before producing signs and symptoms. Parameningeal tumors may present with cranial nerve dysfunction, symptoms of sinusitis, ear discharge, headaches, and facial pain. Orbital tumors often present with orbital swelling and proptosis. Extremity tumors generally present as a rapidly enlarging, firm mass in the relevant tissue. The cancer's prevalence in the head, face, and neck will often allow for earlier signs of the disease simply due to the obvious nature of tumors in these locations. Despite the varying presentation and typically aggressive nature of the disease, RMS has the potential to be diagnosed and treated early. The fourth IRSG study found that 23% of patients were diagnosed in time for a complete resection of their cancer, and 15% had resection with only minimal remnants of the diseased cells.

A lipoma is a benign tumor made of fat tissue. They are generally soft to the touch, movable, and painless. They usually occur just under the skin but occasionally may be deeper. Most are less than 5 cm in size. Common locations include upper back, shoulders, and abdomen. A few people have a number of lipomas.

The cause is generally unclear. Risk factors include family history, obesity, and not enough exercise. Diagnosis is typically based on a physical exam. Occasionally medical imaging or tissue biopsy is used to confirm the diagnosis.

Treatment is typically by observation or surgical removal. Rarely the condition may recur following removal, however, this can generally be managed with repeat surgery. They are not generally associated with a future risk of cancer.

About 2% of people are affected. Lipomas typically occur in adults between 40 to 60 years of age. Males are more often affected than females. They are the most common non-cancerous soft tissue tumor. The first use of the term "lipoma" to describe these tumors was in 1709.

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.

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.

Almost all women present with uterine fibroids, approximately 76% with dermal manifestations and 10-16% with renal tumors.

The uterine fibroids tend to occur at younger age and larger and more numerous than in general population. They may be distinguishable from sporadic fibroids by special histological features such as prominent nucleoli with perinucleolar halos.

The skin presentation is of asymmetrical, reddish-brown nodules or papules with a firm consistency, predominantly located on the limbs (multiple cutaneous leiomyoma), although they may occur anywhere, including the face. The lesions, which are typically painful and most often present during the third decade of life, are piloleiomyomata—a benign smooth muscle tumour arising from the arrectores pilorum muscles of the skin. These tumours may also arise in the tunica dartos of the scrotum and the mammillary muscle of the nipple (genital leiomyoma), the smooth muscle of blood vessels (angioleiomyoma) and the lung (pulmonary lymphangioleiomyomatosis). A pseudo-Darier sign may be present.

The renal cell carcinoma tends to be of the papillary (type 2) form and tends to occur more commonly in women than men with this syndrome. These cancers present earlier than is usual for renal cell carcinomas (typically in the twenties and thirties) and to be at relatively advanced stages at presentation. Tumours have rarely been reported in children. These tumours occur in ~20% of those with this mutation suggesting that other factors are involved in the pathogenesis.

MTSCC has a gross appearance close to papillary RCC. Microscopically, it has three histologic components: mucin, tumor cells forming tubules, and spindle cells. It is characterized by the proliferation of cuboidal and spindle cells arranged in tubular or sheet-like arrays, typically with a mucinous or myxoid background.

The ovarian fibroma, also fibroma, is a benign sex cord-stromal tumour.

Ovarian fibromas represent 4% of all ovarian neoplasms. They tend to occur mostly during perimenopause and postmenopause, the median age having been reported to be about 52 years, and they are rare in children. Lesions tend to be asymptomatic. If symptoms are present, the most common one is abdominal pain.

On gross pathology, they are firm and white or tan. On microscopic examination, there are intersecting bundles of spindle cells producing collagen.

There may be thecomatous areas (fibrothecoma). The presence of an ovarian fibroma can cause ovarian torsion in some cases.

GP consist of three components (1) ganglion cells, (2) epithelioid cells (neuroendocrine-like), and (3) spindle cells (schwannoma-like). The microscopic differential diagnosis includes poorly differentiated carcinoma, neuroendocrine tumour and paraganglioma.

GPs may be sporadic or arise in the context neurofibromatosis type 1.

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.

Benign neoplasms are typically but not always composed of cells which bear a strong resemblance to a normal cell type in their organ of origin. These tumors are named for the cell or tissue type from which they originate, followed by the suffix "-oma" (but not -carcinoma, -sarcoma, or -blastoma, which are generally cancers). For example, a lipoma is a common benign tumor of fat cells (lipocytes), and a chondroma is a benign tumor of cartilage-forming cells (chondrocytes). Adenomas are benign tumors of gland-forming cells, and are usually specified further by their cell or organ of origin, as in hepatic adenoma (a benign tumor of hepatocytes, or liver cells). Teratomas contain many cell types such as skin, nerve, brain and thyroid, among others, because they are derived from germ cells. Hamartomas are a group of benign tumors that have relatively normal cellular differentiation but the architecture of the tissue is disorganised. There are a few cancers with 'benign-sounding' names which have been retained for historical reasons, including melanoma (a cancer of pigmented skin cells, or melanocytes) and seminoma (a cancer of male reproductive cells). Skin tags, vocal chord polyps and hyperplastic polyps of the colon are often referred to as benign but they are actually overgrowths of normal tissue rather than neoplasms.

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.

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.

Pleomorphic adenoma is a common benign salivary gland neoplasm characterised by neoplastic proliferation of parenchymatous glandular cells along with myoepithelial components, having a malignant potentiality. It is the most common type of salivary gland tumor and the most common tumor of the parotid gland. It derives its name from the architectural Pleomorphism (variable appearance) seen by light microscopy. It is also known as "Mixed tumor, salivary gland type", which describes its pleomorphic appearance as opposed to its dual origin from epithelial and myoepithelial elements.

Cystic nephromas are often asymptomatic. They are typically discovered on medical imaging incidentally (i.e. an incidentaloma).

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

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.

The tumor is usually solitary and presents as a slow growing, painless, firm single nodular mass. Isolated nodules are generally outgrowths of the main nodule rather than a multinodular presentation. It is usually mobile unless found in the palate and can cause atrophy of the mandibular ramus when located in the parotid gland. When found in the parotid tail, it may present as an eversion of the ear lobe. Though it is classified as a benign tumor, pleomorphic adenomas have the capacity to grow to large proportions and may undergo malignant transformation, to form carcinoma ex-pleomorphic adenoma, a risk that increases with time (9.5% chance to convert into malignancy in 15 years). Although it is "benign" the tumor is aneuploid, it can recur after resection, it invades normal adjacent tissue and distant metastases have been reported after long (+10 years) time intervals.