Clinical features and ultrasound findings of a rare musculoskeletal system disease-neuromuscular choristoma

Neuromuscular Choristoma of the Brachial Plexus Presenting as a Supraclavicular Mass in a Pediatric Patient: A Case Report

CASE

This case demonstrates a 2-year-old boy with a rare benign supraclavicular mass diagnosed as neuromuscular choristoma through open biopsy. Postoperatively, he underwent semiannual surveillance with ultrasound without development of neurological complaints, limb deformity, or recurrence at 2-year follow-up.

CONCLUSION

Neuromuscular choristoma involving the brachial plexus is a rare tumor that should be in the differential diagnosis of pediatric peripheral nerve-based tumors. The intimate association with neural elements limits complete resection. Therefore, open biopsy with partial resection is recommended. While postoperative fibromatosis may occur, open biopsy remains the gold standard for definitive diagnosis. Ultrasound can be used to monitor recurrence.

Neuromuscular choristoma-associated desmoid-type fibromatosis of the brachial plexus: Additional evidence to support a nerve-driven mechanism

BACKGROUND

We have recently described circumferential nerve involvement of neuromuscular choristoma associated with desmoid-type fibromatosis (NMC-DTF) in cases involving the sciatic nerve, supporting a nerve-derived mechanism for the DTF. We wondered whether a similar growth pattern occurs in cases involving the brachial plexus (BP).

METHODS

We reviewed all available magnetic resonance (MR) imaging in patients diagnosed at our institution with NMC or NMC-DTF of the BP. We also performed a literature search of patients with NMC or NMC-DTF of the BP.

RESULTS

In our clinical records, four patients with NMC of the BP were identified, and three developed NMC-DTF. All three patients had MR imaging evidence of circumferential encasement of the BP. In the literature, we identified 15 cases of NMC of the BP, of which 12 had identified NMC-DTF. Four published cases included MR images, and only two were of sufficient quality for review. The single provided image in both cases demonstrated a similar pattern of circumferential encasement of the BP by the NMC-DTF. One additional case report was published without MR images but described circumferential involvement in the surgical findings. One unpublished case of NMC-DTF of the BP from an international radiology meeting also had this circumferential pattern pattern on MRI.

CONCLUSIONS

The MRI findings of circumferential nerve involvement in patients with NMC-DTF of the BP are similar to our previously reported data in patients with NMC-DTF of the sciatic nerve, providing further imaging-based support of a nerve-driven mechanism. Clinical implications are presented based on the proposed pathogenetic mechanism.

Multifocal Desmoid-Type Fibromatosis: Case Series and Potential Relationship to Neuronal Spread

Multifocal desmoid-type fibromatosis (DTF) is very rare and usually regional. We report three cases that initially appeared to be multifocal, but subsequent detailed imaging revealed unsuspected tracking along nerves in two cases. This neural spread is reminiscent of neuromuscular choristoma (NMC), a rare developmental lesion in which mature skeletal muscle cells, or rarely smooth muscle cells, infiltrate and enlarge peripheral nerves. NMC is frequently associated with DTF. These two cases suggest that DTF spread along nerves and appeared as distinct multifocal lesions while actually being contiguous. The third case was felt to represent true multifocal tumor development, possibly due to tumor seeding at the time of chest surgery. The relationship of DTF to NMC is discussed.

Adult neuromuscular choristoma, a rare peripheral nerve pathology: illustrative case

BACKGROUND

Neuromuscular choristomas (NMCs) are rare tumors involving aberrant intercalation of muscle fibers into peripheral nerves, most commonly the sciatic nerve. Although benign, these lesions risk developing into NMCs with desmoid-type fibrosis (NMC-DTFs), aggressive lesions potentially requiring amputation. Currently, information on NMCs and the link between NMCs and NMC-DTFs is limited in adults, with the majority of cases reported in children. We present the case of a 66-year-old male with a sciatic NMC alongside a Preferred Reporting Items for Systematic Reviews and Meta-Analyses-based systematic review of similar cases to better characterize this lesion in the adult population.

OBSERVATIONS

A male presented with 10 years of progressive left lower-extremity weakness and paresthesia, and a mildly enlarged proximal sciatic nerve was discovered on magnetic resonance imaging. He underwent left sciatic fascicular nerve biopsy, with histopathological examination identifying the lesion as an NMC. The literature review revealed that our case, alongside other cases of adults with NMCs, shared characteristics similar to NMCs in the pediatric population.

LESSONS

More comprehensive studies of adults with NMCs are needed, as the current literature contains limited information concerning disease course, diagnostic characteristics, and treatment. Furthermore, NMCs in adults should be handled with care because of the increased likelihood of transformation to NMC-DTF after surgical intervention.

Beyond schwannomas and neurofibromas: a radiological and histopathological review of lesser-known benign lesions that arise in association with peripheral nerves

Peripheral nerve sheath tumors comprise a significant percentage of both benign and malignant soft tissue tumors. The vast majority of these lesions are schwannomas and neurofibromas, which most radiologists are familiar with including the well-described multimodality imaging features. However, numerous additional often under-recognized benign entities associated with nerves exist. These rarer entities are becoming increasingly encountered with the proliferation of cross-sectional imaging, particularly magnetic resonance imaging (MRI). It is important for the radiologist to have a basic understanding of these entities as many have near-pathognomonic MR imaging features as well as specific clinical presentations that when interpreted in concert, often allows for a limited differential or single best diagnosis. The ability to provide a prospective, pre-intervention diagnosis based solely on imaging and clinical presentation is crucial as several of these entities are "do not touch" lesions, for which even a biopsy may have deleterious consequences. To our knowledge, the majority of these benign entities associated with nerves have only been described in scattered case reports or small case series. Therefore, the aim of this article is to provide a radiopathologic comprehensive review of these benign entities that arise in association with nerves with a focus on characteristic MRI features, unique histopathologic findings, and entity specific clinical exam findings/presentation.

PET imaging characteristics of neuromuscular choristoma and associated desmoid-type fibromatosis

BACKGROUND

Neuromuscular choristoma (NMC) is a rare peripheral nerve lesion characterized by abnormal presence of muscle within nerve. Associated desmoid-type fibromatosis (NMC-DTF) often develops. We report ¹⁸F-fluorodeoxyglucose positron emission tomography (FDG PET) characteristics of NMC and NMC-DTF and propose that increased FDG activity within NMCs may be associated with subclinical NMC-DTF or NMC-DTF "precursor" tissue.

METHODS

Our institutional database was searched for all NMC cases. Inclusion criteria were 1) confirmed diagnosis of NMC with or without biopsy, and 2) available PET and MRI studies. PET data included SUVmax and SUVmean of NMCs, contralateral limb normal skeletal muscle and unaffected nerves, and SUVmax of NMC-DTF if present. SUV values were compared using paired t-test. A p value of < 0.05 was considered statistically significant.

RESULTS

Our cohort consisted of 9 patients with NMC, 8 cases involving sciatic nerve and 1 of brachial plexus. On PET imaging, all NMC-affected nerve segments showed significantly higher FDG uptake (SUVmax/mean) compared to both contralateral normal nerve and normal skeletal muscle (all P < 0.05). Similar to sporadic DTF, NMC-DTF was highly FDG-avid (average SUVmax of 4.2). SUVmax in NMC with or without concurrent NMC-DTF did not differ (p = 0.76). Within NMC-affected nerve segment, FDG activity was relatively higher in areas with low T1/T2 MR signal.

CONCLUSION

All NMCs were more FDG avid compared to both normal skeletal muscle and contralateral unaffected nerve, arguing against the presence of heterotopic muscle in NMC as the source of FDG avidity. FDG avidity within NMC may reflect subclinical NMC-DTF or a precursor lesion, as NMC-DTF are highly FDG-avid, and the highest regions of FDG avidity in NMC occurred in regions with MR characteristics associated with NMC-DTF (i.e., lower T1/T2 signal). We believe that the integration of FDG PET with serial MR imaging in patient follow up will clarify its utility in both detection and surveillance of NMC-DTF.