Neurothekeoma | |
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Other names | Bizarre cutaneous neurofibroma, myxoma of nerve sheath, pacinian neurofibroma |
Neurothekeoma histology slide | |
Specialty | Oncology |
A Neurothekeoma (NT) is a type of rare benign cutaneous tumor that usually develops on the head and neck. They often occur in the second and early third decades of life and tend to afflict women more frequently than men. [1] First described by Richard L Gallager and Elson B. Helwig, who proposed the term in order to reflect the presumed origin of the lesion from nerve sheath. [2] Microscopically, the lesions described closely resembled the tumor, "nerve sheath myxoma (NSM)", an entity first described by Harkin and Reed. [3] The latter had, through the years, been variously described as bizarre cutaneous neurofibroma, myxoma of nerve sheath, and pacinian neurofibroma. [4]
Clinically, neurothekeomas present as a solitary nodule of the skin. The most common sites of occurrence are the head and neck and the extremities. The lesions range in size from about 0.5 cm to more than 3 cm. The average patient age is about 25 years, but neurothekeomas may occur at any age. Women are affected about twice often; the male to female ratio is approximately 1:2. [5]
Microscopically, neurothekeoma consists of closely aggregated bundles or fascicles of spindle-shaped cells. The fascicles may or may not have a myxoid background. [6]
Since the time of their first description, it has been reported that neurothekeomas are likely not of nerve sheath origin, as implied by the term. [5] Consequently, neurothekeoma and nerve sheath myxoma are likely not related histogenetically, although they are similar in appearance and in behavior. [5] Based mostly on the quantity of myxoid matrix present, neurothekeomas can have a variety of histologic characteristics, including myxoid, cellular, or mixed-type. The myxoid variety of neurothekeoma has inadvertently included nerve sheath myxoma because to similarity in clinical presentation and histology. However, it appears that the neurothekeoma that Barnhill and Mihm reported in 1990 is a separate and distinct entity from true nerve sheath myxoma. [7] It has been proposed that neurothekeomas are derived from fibrohistiocytic cells rather than the peripheral nerve sheath. [8] [9] [10] [11] Despite having a different histologic appearance, neurothekeomas do not respond with the S100 protein while nerve sheath myxoma do (myxoid, mixed, or cellular).
A rare neuro-ectodermal tumor known as a benign nerve sheath myxoma was originally identified in 1969. [3] In contrast, a cellular variation known as neurothekeoma was characterized in 1980 by Gallager and Helwig. [2] Later on, it was common to use both neurothekeoma and nerve sheath myxoma interchangeably. [12] [13] In 2011, Sheth et al. used microarray analysis to distinguish between neurothekeoma and nerve sheath myxoma based on the genetic expression of the cells. [14] Nerve sheath myxoma is more frequent among young people without gender preference. Between 30 and 40 years of age is when the incidence peaks. [15] The head and neck are rarely affected by the tumor, which is more usually seen in the upper limb. [16] Young women are twice as likely as males to get neurothekeoma, and it usually affects the head and neck rather than the hands. [9] While neurothekeoma can afflict females from infancy to old age with a peak incidence in the twenties, nerve sheath myxoma has a peak incidence in the fourth decade. [17]
Lesions are often a singular subcutaneous dome-shaped papule or nodule measuring less than 2 cm and may be skin-colored, pink to tan, or red to brown. Most lesions are asymptomatic although some may present with pain upon pressure. The lesions tend to grow slowly and are usually superficially located, with rare, deeper involvement of subcutaneous fat or skeletal muscle. The head and neck are the most common locations, but neurothekeomas may also be seen on the shoulder or upper extremities, while involvement of the mucosa is rare. [18] [8] [9] [19] [20] [21] [22]
Surgical excision is the treatment of choice. [23] There have been reports of neurothekeomas exhibiting atypical features, raising concern for their potential for aggression even though the majority of these tumors are small (less than 1 cm), have relatively bland histology, little to no cytologic atypia, and only minimal extension into surrounding fat or skeletal muscle. Clinical size more than 1 cm, pleomorphism and enhanced mitotic activity in the cytology, infiltration into skeletal muscle or subcutaneous fat, and vascular invasion are reported as unusual characteristics. Despite the presence of unusual characteristics, documented recurrence rates after total surgical excision are very low. [18] [24] [25]
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 (2.0 in) in size. Common locations include upper back, shoulders, and abdomen. It is possible to have several lipomas.
Liposarcomas are the most common subtype of soft tissue sarcomas, accounting for at least 20% of all sarcomas in adults. Soft tissue sarcomas are rare neoplasms with over 150 different histological subtypes or forms. Liposarcomas arise from the precursor lipoblasts of the adipocytes in adipose tissues. Adipose tissues are distributed throughout the body, including such sites as the deep and more superficial layers of subcutaneous tissues as well as in less surgically accessible sites like the retroperitoneum and visceral fat inside the abdominal cavity.
Hemangioendotheliomas are a family of vascular neoplasms of intermediate malignancy.
A schwannoma is a usually benign nerve sheath tumor composed of Schwann cells, which normally produce the insulating myelin sheath covering peripheral nerves.
Granular cell tumor is a tumor that can develop on any skin or mucosal surface, but occurs on the tongue 40% of the time.
Angiomyxoma is a myxoid tumor involving the blood vessels.
A hibernoma is a benign neoplasm of vestigial brown fat. They were first described under the name ‘pseudolipoma’ by the German physician H. Merkel in 1906 and the term hibernoma was proposed by the French anatomist Louis Gery in 1914 because of its resemblance to brown fat in hibernating animals.
Plexiform fibrohistiocytic tumor is a rare tumor that arises primarily on the upper extremities of children and young adults.
Atypical fibroxanthoma (AFX) of the skin is a low-grade malignancy related to malignant fibrous histiocytoma, which it resembles histologically. Atypical fibroxanthoma manifests as a hard, pink or red papule or nodule that grows over the course of several months and may bleed or ulcerate. They typically occur on the head and neck. Atypical fibroxanthoma is usually asymptomatic.
Spindle cell lipoma is an asymptomatic, slow-growing subcutaneous tumor that has a predilection for the posterior back, neck, and shoulders of older men.
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.
A cutaneous myxoma, or superficial angiomyxoma, consists of a multilobulated myxoid mass containing stellate or spindled fibroblasts with pools of mucin forming cleft-like spaces. There is often a proliferation of blood vessels and an inflammatory infiltrate. Staining is positive for vimentin, negative for cytokeratin and desmin, and variable for CD34, Factor VIIIa, SMA, MSA and S-100.
A superficial acral fibromyxoma is a type of myxoma and is a rare cutaneous condition characterized by a mesenchymal neoplasm that typically occurs on the digits of middle-aged adults.
Low-grade fibromyxoid sarcoma (LGFMS) is a rare type of low-grade sarcoma first described by H. L. Evans in 1987. LGFMS are soft tissue tumors of the mesenchyme-derived connective tissues; on microscopic examination, they are found to be composed of spindle-shaped cells that resemble fibroblasts. These fibroblastic, spindle-shaped cells are neoplastic cells that in most cases of LGFMS express fusion genes, i.e. genes composed of parts of two different genes that form as a result of mutations. The World Health Organization (2020) classified LGFMS as a specific type of tumor in the category of malignant fibroblastic and myofibroblastic tumors.
Rhabdomyoma is a benign mesenchymal tumor of skeletal muscle, separated into two major categories based on site: Cardiac and extracardiac. They are further separated by histology: fetal, juvenile (intermediate), and adult types. Genital types are recognized, but are often part of either the fetal or juvenile types. The fetal type is thought to recapitulate immature skeletal muscle at about week six to ten of gestational development.
An intraneural perineurioma is a rare benign tumor within the sheath of a single nerve that grows but typically does not recur or metastasize. These lesions are only composed of perineurial cells, cloned from a single cell. They are distinct from schwannoma and neurofibroma.
A myxoid tumor is a connective tissue tumor with a "myxoid" background, composed of clear, mucoid substance.
Ectomesenchymal chondromyxoid tumor (ECT) is a benign intraoral tumor with presumed origin from undifferentiated (ecto)mesenchymal cells. There are some who think it is a myoepithelial tumor type.
Acral myxoinflammatory fibroblastic sarcoma (AMSF), also termed myxoinflammatory fibroblastic sarcoma (MSF), is a rare, low-grade, soft tissue tumor that the World Health Organization (2020) classified as in the category of rarely metastasizing fibroblastic and myofibroblastic tumors. It is a locally aggressive neoplasm that often recurs at the site of its surgical removal. However, it usually grows slowly and in only 1–2% of cases spreads to distant tissues.
Angiofibroma of soft tissue (AFST), also termed angiofibroma, not otherwise specified, is a recently recognized and rare disorder that was classified in the category of benign fibroblastic and myofibroblastic tumors by the World Health Organization in 2020. An AFST tumor is a neoplasm that was first described by A. Mariño-Enríquez and C.D. Fletcher in 2012.