OBJECTIVE: Benign triton tumors (BTTs) in the pediatric population are extremely rare occurrences. Paucity of data on BTTs poses both diagnostic and therapeutic challenges, particularly when found intracranially.
METHODS: A case report of a 10-year-old male diagnosed with incidental maxillary trigeminal (V2) BTT is presented. We discuss radiographic and histopathological interpretations. Furthermore, we provide a brief review of current literature and historical background on pediatric trigeminal BTT diagnosis, histopathology, and management.
RESULTS: Successful gross total resection of the tumor was achieved via Dolenc approach to the cavernous sinus. Management options with consideration of outcomes from the few prior cases reported in the literature are presented.
CONCLUSIONS: Treatment of trigeminal nerve tumors requires a broad differential diagnosis and understanding rare tumors is essential in the diagnosis and treatment algorithm.

BACKGROUND: Neuromuscular choristoma (NMC) is a rare peripheral nerve lesion that is composed of ectopic mature muscle fibers and nerve fascicles, typically involving major nerve roots or trunks, such as the cranial nerves, brachial plexus, and sciatic nerves. The onset of NMC frequently occurs in the first decade of life. Here, we present the first documented case of a case of esophageal NMC in an adult patient.
METHODS: A 46-year-old male patient presented in 2018 with a submucosal tumor of the esophagus. Upon presentation, the tumor was approximately 10 mm in diameter, covered by normal mucosa, and located in the left posterior wall of the esophagus in a position that was 30 cm from the incisor. The tumor was discovered incidentally during gastroscopic examination. In March 2021, endoscopic re-examination revealed no significant changes in the tumor. Endoscopic ultrasound revealed an oval hypoechoic mass with a homogeneous internal echo that originated from the muscularis propria with a maximum cross section of 13 mm × 6 mm. Resection was performed under gastroscopy. The resection specimen was 12 mm × 5 mm in size and was a well-demarcated, elastic, hard, and tough with a gray section. Histologically, the specimen consisted of an abundance of smooth muscle fiber bundles intercalated among nerve fibers, but without malignancy. Immunohistochemical examinations revealed positivity for S-100 protein, caldesmon, NSE and desmin, but negativity for CD117, DOG-1, HMB45, and Melan A. There was also aberrant nuclear localization of beta-catenin. Collectively, these findings led to a diagnosis of esophageal NMC.
CONCLUSIONS: NMC is extremely rare, especially esophageal NMC, and is very challenging to accurately diagnose prior to resection. It is important that we can differentiate NMC from other types of tumors.

OBJECTIVE: Benign tumors with skeletal muscle differentiation are rare and their characterization in the literature is limited. We present a series of twelve pediatric benign tumors with rhabdomyomatous differentiation including seven rhabdomyomatous mesenchymal hamartomas, four fetal rhabdomyomas, and one benign triton tumor, analyzing myogenic markers as well as clinicopathologic and molecular features. A review of the literature was also performed with an emphasis on myogenic marker expression and correlation with molecular features.
RESULTS: Cases obtained from three tertiary pediatric hospitals were retrospectively reviewed. Eleven of twelve cases expressed myogenin in rare to greater than 15% of cells. Five of nine cases had rare to 70-80% of cells positive for MyoD1. One fetal rhabdomyoma demonstrated homozygous deletions in ZEB2. The benign triton tumor harbored a CTNNB1 mutation. Review of the literature identified 160 pediatric benign tumors with skeletal muscle differentiation of which 9 reported myogenin positivity.
CONCLUSIONS: Myogenin and MyoD1 may be variably expressed in benign lesions with skeletal muscle differentiation. Recognition of key morphologic features remains critical to diagnose these lesions and, in rhabdomyoma, to exclude malignancy. Our series expands the knowledge of the relationship between rhabdomyoma and rhabdomyosarcoma (RMS) by identifying a shared molecular alteration in ZEB2.

Benign triton tumor (BTT) or neuromuscular hamartoma is an uncommon tumor composed of mature neural and well-differentiated striated muscular elements. Its development is exceptionally rare in the adult and head region. This report describes a case of adulthood BTT that occurred in the orbit. The patient was a 53-year-old woman who presented with right periorbital swelling and pain in eyeball over 2 months. Magnetic resonance imaging revealed a well-enhancing mass surrounding optic nerve and ocular muscles in the right retrobulbar area. The tumor was subtotally removed via transcranial approach. Its pathological diagnosis was confirmed to be a neuromuscular hamartoma. She developed diplopia postoperatively. Adulthood BTT should be considered in the differential diagnosis of head and neck tumors. It is also important to make adequate therapeutic strategy to avoid postoperative neural dysfunction.

Benign Triton tumor (neuromuscular choristoma) is a rare mass that most commonly occurs as a multinodular expansion of tissue in or around large nerves. Intracranial occurrence is uncommon. We report on a 4-year-old girl presenting with a right-sided facial mass and trismus. Imaging revealed a large, complex mass extending from the ventral aspect of the pons, along the trigeminal nerve, through the foramen ovale, and into the right infratemporal fossa. The lesion was partially enhancing, invaded adjacent infratemporal musculature, was associated with marked overgrowth of the right coronoid process, and induced bony erosion of the middle cranial fossa. After needle biopsy, a multidisciplinary team, including plastic surgery, otolaryngology, and neurosurgery, performed a combined, multistep, single-day surgical approach for resection. Unique to this case was the resection of the coronoid process, a modified middle fossa intradural and extradural approach, coupled with a transfacial infratemporal approach. Microscopically, the resected tissue showed skeletal muscle, fibrous tissue, and nerve in a disorganized arrangement characteristic of a benign Triton tumor. We present this case to illustrate diagnostic clues and pitfalls in the preoperative evaluation of a benign Triton tumor. We also highlight the pathologist\'s role as a partner in a multidisciplinary approach to diagnosis and treatment of this rare pediatric mass, potentially the largest Triton tumor in the head reported to date.

Soft-tissue tumors known as \"triton\" tumors are rare lesions containing neural tissue and skeletal muscle at varying levels of maturity and malignant potential. Benign triton tumors, also called \"neuromuscular choristomas\" or \"neuromuscular hamartomas,\" consist of neural tissue containing mature skeletal muscle in intimate relationship with peripheral nerve. These tumors are rare in the head and neck in children. Ectomesenchymomas are similar tumors consisting of a malignant mesenchymal component, usually embryonal rhabdomyosarcoma, and a neuroectodermal component represented by mature ganglion cells or primitive neuroblastic/neuroectodermal foci (primitive ectomesenchymoma). Benign triton tumors have been regarded as benign, whereas ectomesenchymomas have been operationally considered to be variants of rhabdomyosarcoma. We present here a unique case that combines features of these 2 entities in a recurrent lesion on the tongue of a 35-month-old girl. This lesion raises questions about the \"benign\" nature of benign triton tumor and its possible relationship to ectomesenchymoma.