Bizarre parosteal osteochondromatous proliferation (Nora's lesion): two cases

The lesion Nora described in 1983 as a bizarre parosteal osteochondromatous proliferation (BPOP) is a member of a group of osteocartilaginous surface lesions. BPOP is infrequent but new cases are regularly reported. We report two new cases with an unusual localization (ilion and distal humerus) and unusual size (9 cm for the iliac lesion). In light of these cases and reports in the literature, the main differential diagnoses of BPOP are exostosis and parosteal osteosarcoma.     

Subungual exostoses.

From 1910 through 1975, forty-four patients with subungual exostoses were seen at the Mayo Clinic. Thirty-four of them had the exostosis on the great toe. Forty-three of the patients were treated by local excision and one was treated by amputation of the hallux. Five patients had local recurrence. None of the tumors underwent malignant change. Histologically, the tumors consisted of a proliferating fibrocartilaginous gap that merged into mature trabecular bone at its base. The growth in the cap was so active that is sometimes mimicked sarcoma, but no true anaplasia was seen. The subungual exostoses were uniformly benign, and local excision was the treatment of choice.     

Two distinctive subungual pathologies: subungual exostosis and subungual osteochondroma

BACKGROUND: The purpose of this study was to present features that differentiate subungual exostosis from subungual osteochondroma. METHODS: We treated 11 patients for subungual masses. All were confirmed by radiographic and histologic evaluations to be subungual exostosis or subungual osteochondroma. The study patients comprised eight female and three male patients with a mean age at presentation of 18.7 years (range 1.5 to 70.9). In the five patients with subungual exostosis, three (60%) had a toe lesion, and two (40%) had a finger lesion. In the six patients with subungual osteochondroma, four (67%) had a toe lesion, and two (33%) had finger lesions. We analyzed the clinical features, including trauma history, the existence of infection before surgery, tumor recurrence, and postoperative nail deformity. RESULTS: In all patients, the lesions presented as an exophytic tumor of the nail apparatus, beneath the nail plate, which varied in size from 0.6 x 0.4 cm to 1.2 x 0.9 cm. Excision of these masses produced useful toes or fingers without pain, a tender scar, or nail deformity. Although nails were deformed preoperatively, they grew back without ridges or cracks within 3 to 5 months postoperatively. There were no recurrences based on clinical and radiographic evaluations, and both tumor types showed characteristic radiographic and histologic differences. CONCLUSIONS: Subungual exostosis and subungual osteochondroma are benign but have distinct osseous pathologies. We concluded that subungual exostosis is clinically, developmentally, radiographically, and histologically distinct from subungual osteochondroma.     

Nail Unit Enchondromas and Osteochondromas: A Surgical Approach

The anatomic singularities of the nail unit explain why bony tumors and osseous outgrowths of the distal phalanx quickly interfere with the nail apparatus. Osteochondromas (or exostosis) are benign osteocartilaginous outgrowths most commonly located on the hallux. They are by far the most common bony lesions affecting the nail unit. While frequently considered benign tumors, subungual exostoses are better regarded as reactional osseous outgrowths rather than true tumors. Enchondromas (better named chondromas) are intraosseous tumors whose location at the distal phalanx is rare. Large tumors may be responsible for phalanx deformity.     

Incidence of brachydactyly and hand exostosis in hereditary multiple exostosis

Forty-two radiographs and charts of twenty-two patients with a diagnosis of hereditary multiple exostosis and hand involvement were examined to determine the incidence of hand exostoses and association with brachydactyly. An average of 11.6 exostoses were found per hand. The proximal phalanges and metacarpals are affected in the majority of patients and the thumb and distal phalanges are rarely involved. Most exostoses were located in the juxtaepiphyseal region (61.8%) and typically involved less than 50% of the bone diameter. Brachydactyly can be seen in patients with hereditary multiple exostosis when no exostoses is present; however, the presence of an exostosis results in even more shortening. The location and size of the exostosis had no relationship to increased bone shortening. Operative treatment was required in four of twenty-two patients for debulking and impingement.     

Bizarre parosteal osteochondromatous proliferation (Nora's lesion) in the hand

PURPOSE: The purpose of this study was to review our experience with a benign surface bone lesion referred to as bizarre parosteal osteochondromatous proliferation (BPOP) or Nora's lesion, named for the pathologist who described it in 1983. The lesion may be confused with a variety of tumors, particularly solitary osteochondromas, which are rare. METHODS: The files in the Department of Pathology at the Hospital for Joint Diseases were reviewed over a 21-year period for all surface bone lesions involving the tubular bones in the hand. There were a total of 10 cases of BPOP compared with only a single case of an osteochondroma. RESULTS: Radiographs generally showed a well-marginated uniformly dense mass arising from the surface of the affected bone without any disruption in its bony architecture. Surgical excision is the definitive treatment and included the fibrous pseudocapsule over the lesion, any periosteal tissue beneath the lesion, and any area of the cortex of the host bone that appeared abnormal. Although in the medical literature the recurrence rate for BPOP is high, we had only one recurrence in our series. CONCLUSIONS: BPOP is a benign surface bone lesion that may be confused with benign and malignant tumors. Although there is a cleavage plane between the lesion and host bone, we recommend excising the pseudocapsule over the lesion, any periosteal tissue beneath the lesion, and decorticating any abnormal-appearing areas in the underlying host bone. This may explain the low recurrence rate in our series.     

Multiple exostosis: a short study of abnormalities near the growth plate

The pathogenesis of multiple exostosis has been controversial with many theories put forward including the structural/mechanical theory, which emphasizes that the osteochondroma arises in the displaced growth plate cartilage penetrating a defective periosteum. Recently, molecular genetics has offered the neoplastic model with tumor suppressor genes implicated in the development and pathogenesis of exostosis. In this study, we demonstrated the spectrum of histological abnormalities in the developing exostosis present on the surface of the bone at the physis. Seven skeletally immature patients with multiple exostoses were used in this study. The patients' families were advised of and consented to the proposed study. Coincident with removal of symptomatic exostoses that was adjacent to the physis, a thin strip of bone with overlying periosteum was removed to include the edge of the physis. This was followed by formalin fixation and routine paraffin embedding. We demonstrated the earliest lesion as a microchondroma within the periosteum adjacent to the normal physis (also called the 'groove of Ranvier'). More mature progressively larger lesions showing enchondral ossification were seen distally. The periosteum and the perichondrium were intact with normal physis. Our observations give support to the fact that precursor cells in the periosteum adjacent to the physis (also called the 'groove of Ranvier') gives rise to the chondrocytes that clonally expands and develops into exostosis.     

Bizarre parosteal osteochondromatous proliferation of bone (BPOP): an unusual foot mass in a child

This report describes an unusual case of bizarre parosteal osteochondromatous proliferation of bone (BPOP) which developed in the foot of an eight year-old child. Also described as Nora's lesion, BPOP is a rare benign bone tumor found most commonly in the hands and feet with a radiographic appearance occasionally confused with malignancy. Resembling osteochondromas at first glance, these lesions have a distinct radiographic and histologic appearance that permits differentiation from other benign lesions or low-grade malignant tumors. Treatment of BPOP consists of simple excision, although there is high rate of recurrence. Despite this high recurrence rate, there have been no reported metastases and local excision is still recommended.     

Manifestations of hereditary multiple exostoses

The solitary osteochondroma, a common pediatric bone tumor, is a cartilage-capped exostosis. Hereditary multiple exostosis is an autosomal dominant disorder manifested by the presence of multiple osteochondromas. Linkage analysis has implicated mutations in the EXT gene family, resulting in an error in the regulation of normal chondrocyte proliferation and maturation that leads to abnormal bone growth. Although exostoses are benign lesions, they are often associated with characteristic progressive skeletal deformities and may cause clinical symptoms. The most common deformities include short stature, limb-length discrepancies, valgus deformities of the knee and ankle, asymmetry of the pectoral and pelvic girdles, bowing of the radius with ulnar deviation of the wrist, and subluxation of the radiocapitellar joint. For certain deformities, surgery can prevent progression and provide correction. Patients with hereditary multiple exostosis have a slight risk of sarcomatous transformation of the cartilaginous portion of the exostosis.     

A giant subungual exostosis perforating through skin of the toe

Subungual exostosis is typically an uncommon, benign, bony tumor of cartilaginous bone that usually occurs as a solitary, solid lesion under the nail of the first toe or the fingernail. It may be difficult to diagnose subungual exostosis from a clinical presentation and it should be confirmed by radiographic examination. The treatment is surgical excision. It is essential to see normally cancellous bone under the area of excision to ensure that the tumor does not recur. In this article, our goal is to present a subungual exostosis case of the first toe, detailing diagnosis, pathologic findings and surgical management.     

A painful subungual nodule: subungual exostosis

Subungual exostosis is an acquired, benign, often painful, and nearly always solitary bone tumor usually occurring in the dorsal medial aspect of the phalanges. An eighteen-year-old male patient presented with a progressively enlarging mass and pain that developed over two years in the distal medial aspect of the right first toe. Conventional radiographs, computed tomography, and histopathologic findings showed subungual exostosis. Complete removal of the tumor was performed including its base in the cortex of the phalanx. No recurrence was observed during a follow-up of 11 months. It was emphasized that clinical presentation of subungual exostosis may resemble other benign or malignant bone tumors.     

Correlative radiographic, scintigraphic, and histological evaluation of exostoses

We reviewed the cases of twenty-four patients with solitary or multiple exostoses to correlate their radiographic, scintigraphic, and histological evaluations. We studied twenty-five excised lesions, two of them exostotic chondrosarcomas, from twenty-two patients. There were two patterns of bone-scan activity and there was a direct correlation between enchondral bone formation and radionuclide uptake in all patients, both skeletally immature and mature. So-called quiescent lesions--those with inactive scans--were those that lacked histological evidence of enchondral bone formation. Those with increased uptake--active exostoses--all demonstrated active formation of enchondral bone. Evidence of active exostotic growth could be demonstrated on bone scans well beyond the time of skeletal maturity. The bone scan did not qualitatively differentiate the benign active exostoses from the two lesions with malignant degeneration. Increased uptake related to enchondral bone formation was a feature of both. An inactive scan, however, seemed to exclude the possibility of malignant degeneration in the exostosis.     

The Taniguchi classification in cases of multiple cartilaginous exostoses]

27 patients treated surgically at Child Orthopaedic Clinic of Pomeranian Medical Academy between 1974-1996 for multiple cartilaginous exostosis (Aclasia Diaphysealis Keith) were classified into three groups according to the Taniguchi classification. This classification is based on whether multiple cartilaginous exostoses are present on distal forearm. Group I--no involvement of the distal forearm (n = 2), in group II involvement of the distal forearm without shortening of either bone (n = 7) was stated. Group III consists of members with involvement of the distal forearm with shortening the radius or the ulna (n = 18). Groups were compared with regard to: number of lesions, distribution of exostoses in different body areas, age of onset of the Keith disease, height of children, presence of valgus deformity of the ankle, dislocation of the radial head and presence of exostoses around hip area. This classification should be useful in estimating severity of Keith disease, identifying cases at high risk for complications like dislocation of the radial and malignant transformation.     

Protruded and nonprotruded subungual exostosis: Differences in surgical approach

Background:

In subungual exostosis surgery, repair of the damaged nail bed and surgical excision of the mass without damaging the nail bed is important. The ideal method of surgery is still unclear. This study is done to qualify the effects of different surgical methods on outcome measures in different types of subungual exostosis.

Materials and Methods:

Fifteen patients, operated with a diagnosis of subungual exostosis between January 2008 and June 2012, were evaluated. Protruded masses were excised with a dorsal surgical approach after the removal of the nail bed and nonprotruded masses were excised through a“fish-mouth” type of incision.

Results:

The mean age of the patients in protruded subungual exostosis group was 17.3 years (range 13-22 years) and this group consisting of seven female and two male patients. The patients were followed up for a mean of 14.1 ± 4.8 months. The mean age of the patients in the nonprotruded subungual exostosis group was 14.6 years (range 13-16 years) and consisting of six female patients. The patients were followed up for a mean of 11.6 ± 2.9 months. The results were positively affected by changing the surgical approach depending on whether or not the exostosis is protruded from the nail bed. All patients had healthy toe nails in the postoperative period without any signs of recurrence.

Conclusions:

In patients with a protruded subungual exostosis, the mass should be removed by a dorsal approach with the removal of the nail and injury to the nail bed should be repaired. In patients with a nonprotruded subungual exostosis, the mass should be excised through a “fish-mouth” type incision at the toe tip without an iatrogenic damage.     

EXT 1 gene mutation induces chondrocyte cytoskeletal abnormalities and defective collagen expression in the exostoses.

Hereditary multiple exostoses (HME), an autosomal skeletal disorder characterized by cartilage-capped excrescences, has been ascribed to mutations in EXT 1 and EXT 2, two tumor suppressor-related genes encoding glycosyltransferases involved in the heparan sulfate proteoglycan (HSPG) biosynthesis. Taking advantage of the availability of three different exostoses from a patient with HME harboring a premature termination codon in the EXT 1 gene, morphological, immunologic, and biochemical analyses of the samples were carried out. The cartilaginous exostosis, when compared with control cartilage, exhibited alterations in the distribution and morphology of chondrocytes with abundant bundles of actin filaments indicative of cytoskeletal defects. Chondrocytes in the exostosis were surrounded by an extracellular matrix containing abnormally high amounts of collagen type X. The unexpected presence of collagen type I unevenly distributed in the cartilage matrix further suggested that some of the hypertrophic chondrocytes detected in the cartilaginous caps of the exostoses underwent accelerated differentiation. The two mineralized exostoses presented lamellar bone arrangement undergoing intense remodeling as evidenced by the presence of numerous reversal lines. The increased electrophoretic mobility of chondroitin sulfate and dermatan sulfate proteoglycans (PGs) extracted from the two bony exostoses was ascribed to an absence of the decorin core protein. Altogether, these data indicate that EXT mutations might induce a defective endochondral ossification process in exostoses by altering actin distribution and chondrocyte differentiation and by promoting primary calcification through decorin removal.     

A unique presentation of non-Hodgkin's lymphoma in the foot.

Non-Hodgkin's lymphoma of the foot is a relatively uncommon pedal neoplasm. The authors discuss the etiology, incidence, histology, morphology, metastatic rate, and treatment of this entity. Non-Hodgkin's lymphomas rarely present as destructive lesions of bone; when they do, they usually involve the axial skeleton or proximal long bones. Additionally, the authors present a clinical case reporting findings of Non-Hodgkin's lymphoma after surgical correction of a hammertoe deformity and subungual exostosis. The pathologic microscopic evaluation of the resected bone assisted in diagnosis of this condition.     

Dupuytren's (subungual) exostosis

Because it may produce a bewildering array of histologic patterns, the clinical entity of subungual exostosis (Dupuytren's exostosis), is sometimes confused with chondrosarcoma. However, this lesion is a distinct entity. It begins as a reactive growth of cellular fibrous tissue and metaplastic cartilage, which undergoes enchondral ossification. The rate of growth may be exuberant, but it is limited. We present a series of 15 cases as well as a review of the literature. Postadolescents and young adults are most commonly affected, and the majority of cases (80%) occur on the dorsal-medial aspect of the great toe. Trauma, whether chronic or acute, and infection are frequent inciting factors. The radiologic picture is consistent and can be diagnostic. In more than half our cases, chondrosarcoma was suspected initially. However, if the entire clinical picture is evaluated, the histologic findings should not lead to confusion with a malignant process. This acquired exostosis is benign; local excision is curative. However, recurrence is common (53%) after incomplete excision or when the lesion has not achieved full maturation.     

Heparan sulfate abnormalities in exostosis growth plates

Hereditary multiple exostoses (HME), a condition associated with development and growth of bony exostoses at the ends of the long bones, is caused by germline mutations in the EXT genes. EXT1 and EXT2 function as glycosyltransferases that participate in the biosynthesis of heparan sulfate (HS) to modify proteoglycans. HS proteoglycans, synthesized by chondrocytes and secreted to the extracellular matrix of the growth plate, play critical roles in growth plate signaling and remodeling. As part of studies to delineate the mechanism(s) by which an exostosis develops, we have systematically evaluated four growth plates from two HME and two solitary exostoses. Mutational events were correlated with the presence/absence and distribution of HS and the normally abundant proteoglycan, perlecan (PLN). DNA from the HME exostoses demonstrated heterozygous germline EXT1 or EXT2 mutations, and DNA from one solitary exostosis demonstrated a somatic EXT1 mutation. No loss of heterozygosity was observed in any of these samples. The chondrocyte zones of four exostosis growth plates showed absence of HS, as well as diminished and abnormal distribution of PLN. These results indicate that, although multiple mutational events do not occur in the EXT1 or EXT2 genes, a complete loss of HS was found in the exostosis growth plates. This functional knockout of the exostosis chondrocytes' ability to synthesize HS chains further supports the observations of cytoskeletal abnormalities and chondrocyte disorganization associated with abnormal cell signaling.     

Solitary exostosis of the thoracic spine. Early diagnosis and treatment.

STUDY DESIGN: A case report. OBJECTIVE: To highlight the importance of early diagnosis and treatment of vertebral exostosis. SUMMARY OF BACKGROUND DATA: Few cases of spinal cord compression caused by solitary thoracic exostoses have been reported. METHOD: A solitary exostosis in the midline of the neural arch of the fifth thoracic vertebra, causing compression of the spinal cord documented on both magnetic resonance and computed tomographic examinations, is reported in a 51-year-old woman who had normal findings in a neurologic examination. RESULTS: The exostosis was successfully excised. CONCLUSION: Accurate preoperative diagnosis of vertebral exostoses is possible using magnetic resonance and computed tomography. Early excision avoids the development of a permanent neurologic deficit.