Bizarre parosteal osteochondromatous proliferation (BPOP), also known as Nora's lesion, is a type of non-cancerous

bone tumor A bone tumor is an abnormal growth of tissue in bone, traditionally classified as noncancerous (benign) or cancerous (malignant). Cancerous bone tumors usually originate from a cancer in another part of the body such as from lung, breast, thyroi ...

belonging to the group of

cartilage tumors Cartilage tumors, also known as chondrogenic tumors, are a type of bone tumor that develop in cartilage, and are divided into non-cancerous, cancerous Cancer is a group of diseases involving Cell growth#Disorders, abnormal cell growth with t ...

. It is generally seen in the tubular bones of the

hand A hand is a prehensile, multi-fingered appendage located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs. A few other vertebrates such as the koala (which has two opposable thumbs on each "h ...

s and

feet The foot ( : feet) is an anatomical structure found in many vertebrates. It is the terminal portion of a limb which bears weight and allows locomotion. In many animals with feet, the foot is a separate organ at the terminal part of the leg made ...

, where it presents with a rapidly enlarging painless lump in a finger or toe. It is composed of

bone A bone is a Stiffness, rigid Organ (biology), organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red blood cell, red and white blood cells, store minerals, provid ...

cartilage Cartilage is a resilient and smooth type of connective tissue. In tetrapods, it covers and protects the ends of long bones at the joints as articular cartilage, and is a structural component of many body parts including the rib cage, the neck an ...

and

spindle cells Von Economo neurons (VENs), also called spindle neurons, are a specific class of mammalian cortical neurons characterized by a large spindle-shaped soma (or body) gradually tapering into a single apical axon (the ramification that ''transmits ...

. Some people report previous trauma. Diagnosis is by

medical imaging Medical imaging is the technique and process of imaging the interior of a body for clinical analysis and medical intervention, as well as visual representation of the function of some organs or tissues (physiology). Medical imaging seeks to rev ...

. Treatment is by surgical excision. Up to 50% recur after surgery. It is rare, and occurs more often in the 20s and 30s. Combined with

subungal exostosis Subungual exostoses are a type of non-cancerous bone tumor of the chondrogenic type, and consists of bone and cartilage. It usually projects from the upper surface of the big toe underlying the nailbed, giving rise to a painful swelling that des ...

, it accounts for less than 5% of cartilage tumors. Males and females are affected equally. The condition was first described by Frederick E. Nora in 1983.

Signs and symptoms

BPOP generally presents with a 1–3 cm painless lump in a

finger A finger is a limb of the body and a type of digit, an organ of manipulation and sensation found in the hands of most of the Tetrapods, so also with humans and other primates. Most land vertebrates have five fingers ( Pentadactyly). Chambers ...

or more frequently a

toe Toes are the digits (fingers) of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being ''digitigrade''. Humans, and other animals that walk on the soles of their feet, are described as being ''plant ...

. Growth can be rapid.

Mechanism

It is composed of

and

. A small number of people have reported previous trauma.

Diagnosis

Medical imaging Medical imaging is the technique and process of imaging the interior of a body for clinical analysis and medical intervention, as well as visual representation of the function of some organs or tissues (physiology). Medical imaging seeks to rev ...

usually shows a well-defined wide-based bony growth on the surface of bone.

Differential diagnosis

BPOP is distinct from subungal exostosis. Conditions that may appear similar to BPOP include: myositis ossficans, ostechondroma, surface osteosarcoma and granulomatous infection.

Treatment

Treatment is by surgical excision.

Outcomes

Up to 50% recur after surgery.

Epidemiology

BPOP is rare. It is most often seen in people in their 20s and 30s. Combined with

, it accounts for less than 5% of cartilage tumors. Males and females are affected equally.

History

Bizarre parosteal osteochondromatous proliferation was first described by Frederick E. Nora in 1983. Generally in the US, it has been thought of as a mouthful and hence it is sometimes referred to as Nora's lesion.

Other animals

In 1998 a report of a similar lesion to BPOP was reported in a

wallaby A wallaby () is a small or middle-sized Macropodidae, macropod native to Australia and New Guinea, with introduced populations in New Zealand, Hawaii, the United Kingdom and other countries. They belong to the same Taxonomy (biology), taxon ...

References

{{DEFAULTSORT:Bizarre parosteal osteochondromatous proliferation Osseous and chondromatous neoplasia