Perineurioma is a rare benign tumor of the peripheral nerve sheath, encompassing intraneural, traditional soft tissue, reticular, and sclerosing variants. Sclerosing perineurioma is a rare variation that predominantly manifests on the hands of young adults, presenting as a tiny, painless subcutaneous tumor. The incidence of pediatric perineurioma is very low, with only a few dozen cases reported in the literature. The primary cause for appointments at the outpatient clinic is a gradually enlarging asymptomatic tumor. The affected areas usually include the thumb (acral location). The lesions are typically solid, well-defined white masses with a fibrous texture, measuring 1.2-4.0 cm in maximum dimension. We present a 2-year-6-month-old male with a sclerosing perineurioma of the left anterior chest wall and delineate the lesion's ultrasonographic and pathological characteristics. This case report illustrates an almost unique pediatric instance of sclerosing perineurioma of the left anterior chest with additional, previously unreported imaging progression since birth. This case report is critical for general pediatrics and pediatric radiology. A description of this case aids in diagnosing extra-acral features of this tumor. Moreover, this case report may improve understanding of the imaging-pathology correlation of this tumor, benefiting both specialists and fellows.

A 7-week-old boy presented to pediatric ophthalmology with a mass inferior to the medial canthus of the OS that was first noticed on day 3 of life. Crigler massages, warm compresses, and moxifloxacin HCl drops were administered without resolution of symptoms. Probing and irrigation for a presumed dacryocystocele were performed, but the nasolacrimal system was patent, and the mass persisted after the procedure. Oculoplastics was consulted for further evaluation and management. On exam, the tear lake was normal, there was no discharge to palpation of either lacrimal sac, and there was no erythema. An MRI was obtained that showed a mass with nonspecific features abutting the lacrimal sac. A gross total resection of the mass was performed, and it was sent for histopathologic evaluation. Pathology results yielded a diagnosis of sclerosing perineurioma, a rare soft tissue tumor previously unreported in the orbit.

Perineurioma (PN) is an uncommon benign peripheral nerve sheath tumor. For the rarity of this tumor in the oral cavity, otolaryngologists and oral surgeons might not be familiar with this entity. Perineuriomas are typically benign and complete excision is deemed adequate management. Thus, their histological recognition is mandatory to avoid unnecessary overtreatment. We report the clinicopathologic findings of an uncommon variant, the Extraneural Sclerosing PN, in an unusual and never described site, the tongue.

In the past decade, there have been major advances in knowledge related to mesenchymal tumors, and new genetic alterations are being delineated. We report a mesenchymal spindle cell neoplasm harboring a novel gene fusion in an infant. Histopathologically, the neoplasm shared some features with sclerosing perineurioma, but immunohistochemically, EMA was negative, whereas GLUT1, NK1-C3, and BCOR were positive. Next-generation sequencing revealed a PCMTD1-pleomorphic adenoma gene 1 (PLAG1) fusion. PLAG1 contributes to the expression of a variety of genes implicated in regulating cell proliferation, and PCMTD1 has been related to the development of certain carcinomas. Recently, other soft tissue tumors in young children associated with PLAG1 fusion variants have been reported. Perhaps, mesenchymal neoplasms presenting PLAG1 fusions with different genes would confirm a specific group (PLAG mesenchymal tumours or "plagomas") in the near future.