The histological and ultrastructural features of Ledderhose and Dupuytren's disease are the same, which supports the hypothesis that they have a common cause and pathogenesis. As with Dupuytren's disease, the root cause(s) of Ledderhose's disease are not yet understood. It has been noted that it is an inherited disease and of variable occurrence within families, i.e. the genes necessary for it may remain dormant for a generation or more and then surface in an individual, or be present in multiple individuals in the same generation with varying degree.

There are certain identified risk factors. The disease is more commonly associated with -

- A family history of the disease

- Higher incidence in males

- Palmar fibromatosis 10-65% of the time.

- Peyronie's disease

- Epilepsy patients

- Patients of diabetes mellitus

There is also a suspected, although unproven, link between incidence and alcoholism, smoking, liver diseases, thyroid problems, and stressful work involving the feet.

The majority of cases occur in the second and third decades, with approximately 75% of cases occurring before the age of 30 years 1,12-15. There is no recognised gender predilection. Examples have however been seen in patients up to the age of 75 years. In some series there is a male predilection 12 whilst in others no such distribution is found 2

Giant-cell tumor of the tendon sheath, also known as giant-cell synovioma and localized nodular tenosynovitis, is a firm lesion, measuring 1 to 3 cm in diameter, and is most commonly attached to the tendons of the fingers, hands, and wrists, with a predilection for the flexor surfaces. Giant-cell tumor of tendon sheaths most often affect the wrist and fingers of males and females from the ages of 20-50 . These tumors are typically painless and can cause cortical erosion. Surgery to remove the tumor is a common treatment, though the tumors tend to recur.

A schwannoma is a usually-benign nerve sheath tumor composed of Schwann cells, which normally produce the insulating myelin sheath covering peripheral nerves.

Chondromyxoid fibroma is a type of cartilaginous tumor.

Most cases are characterised by GRM1 gene fusion or promoter swapping. It can be associated with a translocation at t(1;5)(p13;p13).

A chondromyxoid fibroma (CMF) is an extremely rare benign cartilaginous neoplasm which accounts for < 1% bone tumours.

Stenosing tenosynovitis is most commonly caused by overuse from chronic repetitive activities using the hand or the involved finger. Examples include work activities (e.g., computer use, materials handling) or recreational activities (e.g., knitting, golf, racket sports). Carpenters who use hammers suffer from this as well as those who continuously grip wood or other materials when cutting them due to having to use your hands as a clamp to hold things in place.

Primary stenosing tenosynovitis can be idiopathic, occurring in middle age women more frequently than in men, but can present also in infancy.

Secondary stenosing tenosynovitis can be caused by disease or entities that cause connective tissue disorders including the following:

- Rheumatoid arthritis and psoriatic arthritis—therefore the clinician must assess the hands for rheumatologic deformities.

- Gout

- Diabetes mellitus

- Amyloidosis

- Systemic lupus erythematosus

Others causes may include the following:

- Direct trauma to the site

- During the postpartum period

- Congenital

Schwannomas are homogeneous tumors, consisting only of Schwann cells. The tumor cells always stay on the outside of the nerve, but the tumor itself may either push the nerve aside and/or up against a bony structure (thereby possibly causing damage). Schwannomas are relatively slow-growing. For reasons not yet understood, schwannomas are mostly benign and less than 1% become malignant, degenerating into a form of cancer known as neurofibrosarcoma. These masses are generally contained within a capsule, and so surgical removal is often successful.

Schwannomas can be associated with neurofibromatosis type II, which may be due to a loss-of-function mutation in the protein merlin. They are universally S-100 positive, which is a marker for cells of neural crest cell origin.

Schwannomas of the head and neck are a fairly common occurrence and can be found incidentally in 3–4% of patients at autopsy. Most common of these is a vestibular schwannoma, a tumor of the vestibulocochlear nerve that may lead to tinnitus and hearing loss on the affected side. Outside the cranial nerves, schwannomas may present on the flexor surfaces of the limbs. Rare occurrences of these tumors in the penis have been documented in the literature.

Verocay bodies are seen histologically in schwannomas.

Neurothekeoma is a benign cutaneous tumor first described by Gallager and Helwig, who proposed the term in order to reflect the presumed origin of the lesion from nerve sheath. Microscopically, the lesions described closely resembled the tumor, "nerve sheath myxoma", an entity first described by Harkin and Reed. The latter had, through the years, been variously described as "Bizarre cutaneous neurofibroma", "Myxoma of nerve sheath", and "Pacinian neurofibroma".

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 neurothkeomas may occur at any age. Women are affected about more often; the male to female ratio is approximately 1:2.

Microscopically, neurothekeoma consists of closely aggregated bundles or fascicles of spindle-shaped cells. The fascicles may or may not have a myxoid background.

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. Consequently, neurothekeoma and nerve sheath myxoma are likely not related histogenetically, although they are similar in appearance and in behavior.

Tendon injury and resulting tendinopathy are responsible for up to 30% of consultations to sports doctors and other musculoskeletal health providers. Tendinopathy is most often seen in tendons of athletes either before or after an injury but is becoming more common in non-athletes and sedentary populations. For example, the majority of patients with Achilles tendinopathy in a general population-based study did not associate their condition with a sporting activity. In another study the population incidence of Achilles tendinopathy increased sixfold from 1979-1986 to 1987-1994. The incidence of rotator cuff tendinopathy ranges from 0.3% to 5.5% and annual prevalence from 0.5% to 7.4%.

Surgery is curative despite possible local relapses. Wide resection of the tumor and resection arthrodesis with an intramedullary nail, vertebrectomy and femoral head allograft replacement of the vertebral body, resection of the iliac wing and hip joint disarticulation have been among the performed procedures.

The close resemblance of FCMB to fibrocartilaginous dysplasia has suggested to some scholars that they might be closely related entities, although the latter features woven bone trabeculae without osteoblastic rimming, which is a quite distinctive aspect. Instead the occurrence of epiphyseal plate-like cartilage is peculiar of the former.

Osteofibrous dysplasia is treated with marginal resection with or without bone grafting, depending on the size of the lesion and the extent of bony involvement. However, due to the high rate of recurrence in skeletally immature individuals, this procedure is usually postponed until skeletal maturity.

Fibroma of tendon sheath is a benign tumor that presents as a small subcutaneous nodule that slowly increases in size. The tumors often have a multinodular growth pattern, with individual nodules being composed of bland, slender, spindle-shaped cells (myofibroblasts) in a dense, fibrous matrix.” A common microscopic finding is the presence of elongated, slit-like blood vessels. The lesions nearly always arise in the distal portions of the extremities. They often occur on the fingers, hands, toes, or feet. Although they are benign, they may recur in up to 40% of cases.

Although they may be regarded as a tumor of the skin, the lesions arise from tendons and aponeuroses in superficial sites, and are therefore properly classified as in the category "soft tissue tumor."

The biological nature of Fibroma of tendon sheath is not known, but the category appears to comprise a number of different pathologic processes. It is considered that about one-third of the lesions in this category may be acral variants of the entity, nodular fasciitis.

A nerve sheath tumor is a type of tumor of the nervous system (nervous system neoplasm) which is made up primarily of the myelin surrounding nerves.

A peripheral nerve sheath tumor (PNST) is a nerve sheath tumor in the peripheral nervous system. Benign peripheral nerve sheath tumors include schwannomas and neurofibromas.

A malignant peripheral nerve sheath tumor (MPNST) is a cancerous peripheral nerve sheath tumor.

Patient response to treatment will vary based on age, health, and the tolerance to medications and therapies.

Metastasis occurs in about 39% of patients, most commonly to the lung. Features associated with poor prognosis include a large primary tumor (over 5 cm across), high grade disease, co-existent neurofibromatosis, and the presence of metastases.

It is a rare tumor type, with a relatively poor prognosis in children.

In addition, MPNSTs are extremely threatening in NF1. In a 10-year institutional review for the treatment of chemotherapy for MPNST in NF1, which followed the cases of 1 per 2,500 in 3,300 live births, chemotherapy did not seem to reduce mortality, and its effectiveness should be questioned. Although with recent approaches with the molecular biology of MPNSTs, new therapies and prognostic factors are being examined.

The standard treatment of COC is enucleation and curettage (E&C). Recurrence following E&C is rare.

Fibrocartilaginous mesenchymoma of bone is (FCMB) is an extremely rare tumor first described in 1984. Fewer than 20 cases have been reported, with patient ages spanning from 9 to 25 years, though a case in a male infant aged 1 year and 7 months has been reported. Quick growth and bulky size are remarkable features of this tumor.

Although the origin of the disease is unknown, there is speculation that it is an aggressive healing response to small tears in the plantar fascia, almost as if the fascia over-repairs itself following an injury. There is also some evidence that it might be genetic.

In the early stages, when the nodule is single and/or smaller, it is recommended to avoid direct pressure to the nodule(s). Soft inner soles on footwear and padding may be helpful.

MRI and sonogram (diagnostic ultrasound) are effective in showing the extent of the lesion, but cannot reveal the tissue composition. Even then, recognition of the imaging characteristics of plantar fibromatoses can help in the clinical diagnosis.

Surgery of Ledderhose's disease is difficult because tendons, nerves, and muscles are located very closely to each other. Additionally, feet have to carry heavy load, and surgery might have unpleasant side effects. If surgery is performed, the biopsy is predominantly cellular and frequently misdiagnosed as fibrosarcoma. Since the diseased area (lesion) is not encapsulated, clinical margins are difficult to define. As such, portions of the diseased tissue may be left in the foot after surgery. Inadequate excision is the leading cause of recurrence.

Radiotherapy has been shown to reduce the size of the nodules and reduce the pain associated with them. It is approximately 80% effective, with minimal side-effects.

Post-surgical radiation treatment may decrease recurrence. There has also been variable success in preventing recurrence by administering gadolinium. Skin grafts have been shown to control recurrence of the disease.

In few cases shock waves also have been reported to at least reduce pain and enable walking again. Currently in the process of FDA approval is the injection of collagenase. Recently successful treatment of Ledderhose with cryosurgery (also called cryotherapy) has been reported.

Cortisone injections, such as Triamcinolone, and clobetasol ointments have been shown to stall the progression of the disease temporarily, although the results are subjective and large-scale studies far from complete. Injections of superoxide dismutase have proven to be unsuccessful in curing the disease while radiotherapy has been used successfully on Ledderhose nodules.

Bicipital tenosynovitis is tendinitis or inflammation of the tendon and sheath lining of the biceps muscle. It is often the result of many years of small tears or other degenerative changes in the tendon first manifesting in middle age, but can be due to a sudden injury. Calcification of the tendon, and osteophytes ("bone spurs") in the intertubercular groove can be apparent on x-rays. The condition (which can also occur in dogs) is commonly treated with physical therapy and cortisone and/or surgery.

It is unclear whether the cause of the trigger thumb is congenital or acquired. The occurrence of bilateral incidence and trigger thumbs in both children of twins are an indication for a congenital cause. Trigger thumb in children is also associated with trisomy of chromosome 13. For these reasons it was assumed that trigger thumbs in children are to be of congenital cause. However, more and more evidence which point towards an acquired cause have been found in recent studies. Therefore the name pediatric trigger thumb is also widely used (and currently preferred by some) for the same disorder.

Villonodular synovitis is a type of synovial swelling.

Types include:

- Pigmented villonodular synovitis (PVNS)

- Giant cell tumor of the tendon sheath (GCTS)

Though they have very different names, they have the same histology, and stain positive for CD68, HAM56, and vimentin.

They are sometimes discussed together.

A nonossifying fibroma (also called fibroxanthoma) is a common benign bone tumor in children and adolescents. However, it is controversial whether it represents a true neoplasm or rather a developmental disorder of growing bone. Radiographically, the tumor presents as a well marginated radiolucent lesion, with a distinct multilocular appearance. These foci consist of collagen rich connective tissue, fibroblasts, histiocytes and osteoclasts. They originate from the growth plate, and are located in adjacent parts of the metaphysis and diaphysis of long bones, most often of the legs. No treatment is needed in asymptomatic patients and spontaneous remission with replacement by bone tissue is to be expected.

Multiple nonossifying fibromas occur in Jaffe-Campanacci syndrome in combination with cafe-au-lait spots, mental retardation, hypogonadism, ocular and cardiovascular abnormalities.

Not much research has been done on the epidemiology of congenital trigger thumbs. There are a few reports on the incidence in their respective studies. The most recent data comes from a Japanese study by Kukichi and Ogino where they found an incidence 3.3 trigger thumbs per 1,000 live births in 1 year old children.

In medicine, a desmoplastic fibroma is a benign fibrous tumor of bone, affecting children and young adults, potentially resulting in cortical bone destruction.

It can also occur in the hand.

A famous occurrence of this particular form of the disease involved Italo-Australian Riccardo Torresan in 2011, with 18 cm of femur needing to be removed with the now widely recognized method of "aggressive curettage" being employed.

Osteofibrous dysplasia (also known as ossifying fibroma) is a rare, benign non-neoplastic condition with no known cause. It is considered a fibrovascular defect. Campanacci described this condition in two leg bones, the tibia and fibula, and coined the term. This condition should be differentiated from Nonossifying fibroma and fibrous dysplasia of bone.

The cause of trigger finger is unclear but several causes have been proposed. It has also been called stenosing tenosynovitis (specifically "digital tenosynovitis stenosans"), but this may be a misnomer, as inflammation is not a predominant feature.

It has been speculated that repetitive forceful use of a digit leads to narrowing of the fibrous digital sheath in which it runs, but there is little scientific data to support this theory. The relationship of trigger finger to work activities is debatable and scientific evidence for and against hand use as a cause exist. While the mechanism is unclear, there is some evidence that triggering of the thumb is more likely to occur following surgery for carpal tunnel syndrome. It may also occur in rheumatoid arthritis.