Background: Fibrous cortical defect (FCD) and non-ossifying fibroma (NOF) are incidentally recognised and benign developmental lesions. The objective of this study was to ascertain the clinical manifestations and symptoms of FCDs/NOFs in children and adolescent patients, to characterise the lesions radiologically using X-ray and MRI techniques, and to determine the relationship between physical activity and the condition. Methods: The study included patients under the age of 18 with radiological lesions on their extremities. The lesions were classified as FCD or NOF in accordance with the distinctive imaging features. For each lesion, the bone involved, the site involved, the size of the lesion, and the type of lesion (according to the Ritschl classification) were recorded. In the anamnesis, the patient's presenting complaint, the character of the pain, if any, and the level of activity were investigated. Pain was quantified using the visual analogue scale (VAS) and the 21-Numbered Circle VAS (21-NCVAS). The 21-Numbered Circle Activity Scale (21-NCAS) and the International Physical Activity Questionnaire (IPAQ) were employed for the assessment of physical activity. Results: The study included 34 lesions in 28 children (14 girls/14 boys). There was no difference in age between girls and boys (p = 0.45). According to Ritschl's classification, 18 (52.9%) lesions were stage A, 9 (26.5%) were stage B, and 7 (20.6%) were stage C. The lesion size increased with increasing Ritschl stage (p < 0.02). The main presenting complaint was pain (n = 13, 49.9%). In 21.4% of the children (n = 6), lesions were detected incidentally on radiographs. According to IPAQ, 39.3% of the children were physically inactive. There was a significant negative correlation between 21-NCAS and Ritschl stage (r = -0.51, p < 0.05). Activity decreased as the Ritschl stage increased. There was a significant negative correlation between 21-NCAS and VAS (r = -0.69, p < 0.05). Conclusions: Spontaneous pain was observed in 49.9% of patients diagnosed with FCD/NOF. No correlation was identified between lesion size and the presence or severity of pain. As the severity of pain and Ritschl stage increased, there was a corresponding decrease in physical activity.

RNA sequencing of an aneurysmal benign fibrous histiocytoma with the karyotype 46,XY,t(3;11)(p21;q13),del(6)(p23)[17]/46,XY[2] showed that the t(3;11) generated two fusion genes: LAMTOR1-PRKCD and NUMA1-SFMBT1. RT-PCR together with Sanger sequencing verified the presence of fusion transcripts from both fusion genes. In the LAMTOR1-PRKCD fusion, the part of the PRKCD gene coding for the catalytic domain of the serine/threonine kinase is under control of the LAMTOR1 promoter. In the NUMA1-SFMBT1 fusion, the part of the SFMBT1 gene coding for two of four malignant brain tumor domains and the sterile alpha motif domain is controlled by the NUMA1 promoter. The data support a neoplastic genesis of aneurysmal benign fibrous histiocytoma and indicate a pathogenetic role for LAMTOR1-PRKCD and NUMA1-SFMBT1.

Nonossifying fibromas (NOFs) are benign lesions that unusually occur in the mandible. Nonossifying fibromas are asymptomatic and spontaneous resolution at skeletal maturity. Nonossifying fibromas associated with aneurysmal bone cyst (ABC) are very rare. In this clinical report, NOF secondary to ABC in the mandibular condyle was reported; however, it presents different clinical behavior than the usual NOF. In this case, severe destruction in the mandibular condyle as a characteristic of NOF was seen. In the follow-up period, no recurrence was seen subsequent to treatment of lesion with complete resection. Treatment of NOFs with secondary ABC would require aggressive intervention than the treatment of usual NOF.

Cytogenetic information of non-ossifying fibromas (NOFs) is exceptionally limited. This fact relies, in part, on their benign nature but mainly because most cases evolve undetected or there is no need for surgical intervention. We report the case of a NOF arising in the left tibia of a 14-year-old male with an invariable clonal translocation. The karyotype was denoted as 42-46,XY,t(11;3;14)(q23;p21;p11). There are only two previous reported cases of clonally aberrant NOF. Records from additional cases will be essential to assess whether consistent karyotypic aberrations define this lesion.

Non-ossifying fibroma of bone (NOF) is a common entity, more frequently found in male children and consisting of a solitary eccentric, lytic expanded lesion in the metaphysis of a long bone. The disorder is benign and most often asymptomatic but may result in a fracture requiring therapy. Of some importance is to distinguish NOF from another very similar but smaller lesion, fibrous cortical defect, which is almost always asymptomatic and eccentrically located. Even more striking is a very rarely encountered lesion known as Jaffe-Campanacci syndrome, which also occurs in children who present with typical non-ossifying fibromatous tumors but in multiple sites. In addition, these patients have some systemic and dermal findings resembling those seen in patients with Type 1 neurofibromatosis.

Aneurysmal bone cyst is a benign, cystic lesion of bone composed of blood-filled spaces separated by fibrous septa. Relatively few cases of aneurysmal bone cyst have been cytogenetically characterized, yet abnormalities of the short arm of chromosome 17 appear to be recurrent. In this study, conventional cytogenetic analysis of 43 aneurysmal bone cyst specimens from 38 patients over a 12-year period revealed clonal chromosomal abnormalities in 12 specimens. Karyotypic anomalies of 17p, including a complex translocation and inversion, were identified in eight of these 12 specimens. In an effort to further define the aberrant 17p breakpoint, fluorescence in situ hybridization (FISH) analyses were performed using a series of probe combinations spanning a 5.1 Mb region between the TP53 (17p13.1) and Miller-Dieker lissencephaly syndrome (17p13.3) gene loci. These studies revealed the critical breakpoint locus at 17p13.2, flanked proximally by an RP11-46I8, RP11-333E1, and RP11-457I18 bacterial artificial chromosome (BAC) probe cocktail and distally by an RP11-198F11 and RP11-115H24 BAC and RP5-1050D4 P1 artificial chromosome (PAC) probe cocktail. Overall, abnormalities of the 17p13.2 locus were identified by metaphase and/or interphase cell FISH analysis in 22 of 35 (63%) aneurysmal bone cyst specimens examined including 26 karyotypically normal specimens. These cytogenetic and molecular cytogenetic findings expand our knowledge of chromosomal alterations in aneurysmal bone cyst, further localize the critically involved 17p breakpoint, and provide an alternative approach (ie FISH) for detecting 17p abnormalities in nondividing cells of aneurysmal bone cysts. The latter could potentially be utilized as an adjunct in diagnostically challenging cases.