OBJECTIVE: Chondromyxoid fibroma (CMF) is a rare, benign bone tumour which arises primarily in young adults and is occasionally diagnostically challenging. Glutamate metabotropic receptor 1 (GRM1) gene encodes a metabotropic glutamate receptor and was recently shown to be up-regulated in chondromyxoid fibroma through gene fusion and promoter swapping. The aim of this study was to interrogate cases of CMF for the presence of GRM1 gene rearrangements, gene fusions and GRM1 protein overexpression.
RESULTS: Selected cases were subjected to testing by fluorescent in-situ hybridisation (FISH) with a GRM1 break-apart probe, a targeted RNA sequencing method and immunohistochemical study with an antibody to GRM1 protein. Two cases were subjected to whole transcriptomic sequencing. In 13 of 13 cases, GRM1 protein overexpression was detected by immunohistochemistry using the GRM1 antibody. Of the 12 cases successfully tested by FISH, nine of 12 showed GRM1 rearrangements by break-apart probe assay. Targeted RNA sequencing analysis did not detect gene fusions in any of the eight cases tested, but there was an increase in GRM1 mRNA expression in all eight cases. Two cases subjected to whole transcriptomic sequencing (WTS) showed elevated GRM1 expression and no gene fusions.
CONCLUSIONS: GRM1 gene rearrangements can be detected using FISH break-apart probes in approximately 75% of cases, and immunohistochemical detection of GRM1 protein over-expression is a sensitive diagnostic method. The gene fusion was not detected by targeted RNA sequencing, due most probably to the complexity of fusion mechanism, and is not yet a reliable method for confirming a diagnosis of CMF in the clinical setting.

Surgical treatment of chondromyxoid fibroma of ribs is described. The diagnosis was verified after histological analysis. The patient underwent resection of multinodular tumor of anterolateral thoracic wall invading abdominal cavity via thoracoabdominal access. Postoperative period was uneventful. This case demonstrates the need for total en-bloc resection of tumor with surrounding tissues. Surgery is the only effective method for these patients.
Описан редкий случай хирургического лечения хондромиксоидной фибромы ребер. Диагноз верифицирован окончательно после получения планового гистологического заключения. Пациентке выполнено удаление многоузловой опухоли переднебоковой грудной стенки, прорастающей в брюшную полость, из комбинированного торакоабдоминального доступа. Послеоперационный период протекал без осложнений. Представленный случай демонстрирует необходимость радикального удаления опухоли с окружающими тканями единым блоком. Данные литературы демонстрируют, что единственным эффективным методом лечения данной категории пациентов является хирургический метод.

UNASSIGNED: Chondromyxoid fibroma (CMF) is a rare cartilaginous tumor, accounting for < 1% of benign bone tumors. We report a case of temporomandibular joint (TMJ)-CMF, involving the pterygopalatine space and skull base and discuss its epidemiology, clinical characteristics, and management.
UNASSIGNED: A 56-year-old woman presented with facial asymmetry and progressive mouth opening restriction due to a mass expanding upwardly to the auriculotemporal region. Using digital techniques to determine the lesion\'s boundary and reconstruct the normal glenoid fossa, the temporalis myofascial flap was transplanted between the titanium mesh and condyle to reconstruct the disc after tumor resection.
UNASSIGNED: This case highlights the importance of identifying patients with TMJ-CMF.

The clinical, radiological, and histopathological features of chondromyxoid fibroma can sometimes resemble those of other benign or malignant tumors. Recently, recurrent GRM1 rearrangements have been identified in chondromyxoid fibroma, and GRM1 positivity by immunohistochemistry has emerged as a dependable surrogate marker for this molecular alteration. Phosphaturic mesenchymal tumor is a rare tumor that often exhibits overexpression of fibroblastic growth factor 23 (FGF23) through various mechanisms. In this report, we present a case of GRM1-rearranged chondromyxoid fibroma that also exhibited FGF23 expression via in situ hybridization, posing significant diagnostic challenges during workup of the initial core biopsy. We hope that this case can serve as an educational resource, shedding light on a rare diagnostic pitfall.

Chondromyxoid fibroma is a rare, benign tumor of the bone with excellent prognosis but a high rate of recurrence. We report a patient presenting with pain and a history of chondromyxoid fibroma of the distal left femur previously treated with multiple prior curettage and bone graft procedures. Magnetic resonance imaging and histopathology indicated a recurrence of tumor. Due to the small size of the tumor recurrence and challenges associated with prior open surgery, the patient underwent cryoablation of the lesion with computed tomography guidance. Follow-up 18 months later indicated a resolution of pain and improvement on magnetic resonance imaging, and no concerns after 20 months. To our knowledge, this is the first reported case of chondromyxoid fibroma treated with cryoablation. This case suggests cryoablation could be considered in the setting of recurrent chondromyxoid fibroma for local tumor control.

Chondromyxoid fibroma (CMF) is a rare benign bone tumour. While CMF located entirely on the surface of a bone (i.e. juxtacortical CMF) has been well characterised, CMF has not so far been convincingly documented to arise in soft tissues without connection to an underlying bone.We report a subcutaneous CMF in a 34-year-old male, located on the distal medial aspect of the right thigh without any connection with the femur. The tumour measured 15 mm, it was well-circumscribed and displayed typical morphological features of a CMF. At the periphery, there was a small area of metaplastic bone. Immunohistochemically, the tumour cells were diffusely positive for smooth muscle actin and GRM1, and negative for S100 protein, desmin and cytokeratin AE1AE3. Whole transcriptome sequencing revealed a novel PNISR::GRM1 gene fusion.Our case indicates that CMF should be included in the differential diagnosis of soft tissue (including subcutaneous) tumours composed of spindle/ovoid cells, with a lobular architecture and chondromyxoid matrix. The diagnosis of CMF arising in soft tissues can be confirmed by identifying a GRM1 gene fusion or GRM1 expression by immunohistochemistry.

The surgical resection of the tumor spreading into the cavernous sinus (CS) is complicated and challenging.
We report a left recurrent CS chondromyxoid fibroma occupying the clival-petrous apex-parasellar-suprasellar area, which was totally removed by the micro-endo combination technique via the middle cranial fossa extradural approach.
This case demonstrates the value of the micro-endoscopic combination technique for complicated skull base surgery.

Chondromyxoid fibroma is a rare bone tumor of cartilaginous origin, representing less than 1% of all bone tumors. It preferentially arises in the eccentric location of the metaphysis of a long tubular bone. Juxtacortical locations are reported infrequently in the long bones and even more rarely in short tubular bones, with only three cases documented. Here we present two new cases of juxtacortical chondromyxoid fibroma in the small bones. One was an intracortical osteolytic lesion of the metatarsal bone of the foot with degenerative atypia that histologically should be differentiated from chondrosarcoma. The other was a phalangeal mass protruding into the interphalangeal joint of the hand, which had been labeled mistakenly as a soft tissue mass preoperatively. These cases illustrated that chondromyxoid fibromas have various the manifestations and should be included in the differential diagnosis of an osteolytic lesion or an exophytic mass in the small bones.

BACKGROUND: Craniofacial chondromyxoid fibromas (CMF) are a rare benign tumor of cartilaginous origin. They are commonly misdiagnosed due to the paucity of information on tumor characteristics. We performed a systematic review to characterize CMF located in different regions of the craniofacial skeleton.
METHODS: A search of the literature was executed using the search phrase \"chondromyxoid fibroma\" and included articles from 1990 - 2020. Sixty-eight articles met the inclusion criteria, with a total of 91 patients with analyzable data (22 with calvarial and 69 with sinonasal tumor locations). Descriptive analyses were performed to compare pre-selected characteristics between the two groups.
RESULTS: Sinonasal CMF frequently presented with cranial nerve palsy and expectedly had a high rate of nasal symptoms. Calvarial tumors frequently presented with an external mass and headache. Gross total resection (GTR) was achieved in a higher proportion of cases in the calvarial group versus the sinonasal group (83.3% vs 53.1%). Overall recurrence rate at 17.7% was higher in sinonasal CMF compared to the calvarial tumors at 8.3%. Recurrences after GTR were similar in the sinonasal and calvarial groups (9.7% vs 9.1%). In patients who did not achieve GTR, recurrence was higher in the sinonasal compared to the calvarial group (27.6% vs 0%).
CONCLUSIONS: Craniofacial CMF in calvarial and sinonasal locations have distinct clinical characteristics and response to treatment. Sinonasal lesions tend to have higher recurrence compared to calvarial CMF. Performance of GTR is associated with decreased recurrence in all CMF.

A very rare case of 46-yaer-old woman with chondromyxoid fibroma (CMF) of infralabyrinthine area of temporal bone was described in this article. The only manifestation of this disease was a severe temporary pain in the postauricular area with irradiation in the occipital bone and headache during the last 3 months. A detail description of the CT scan and MRI data was presented. Tumor removing was performed through the retrofacial approach with combination of the microscopic and endoscopic assistance technique, which allows to had a good visualization and controlling of tumor separation from the vital structures with hearing and facial nerve function preserve. Also, we presented a brief review of literature with differential diagnosis of the CMF of the temporal bone, which conducted to minimize the diagnosis mismatches in the otologic and head and neck practice and to optimize the treatment of patients with such tumor.
В статье представлен редкий случай хондромиксоидной фибромы (ХМФ) инфралабиринтного пространства височной кости у 46-летней женщины. Единственным проявлением заболевания была периодическая сильная боль в заушной области с иррадиацией в затылок и головная боль в течение последних 3 мес. Представлены детальные данные визуализирующих исследований височных костей. Новообразование удалено с использованием ретрофациального подхода и эндоскопической техники, что позволило сохранить пациентке слух и избежать травмы лицевого нерва. Кратко представлен обзор литературы и описана дифференциальная диагностика ХМФ височной кости с целью профилактики диагностических ошибок и оптимизации лечения пациентов с данной патологией.