Perineuriomas are a rare form of peripheral nerve sheath tumors, with occurrences in the oral cavity being exceptionally uncommon. This scarcity underscores the clinical significance of each documented case, as it facilitates enhanced diagnostic precision among oral health professionals. We hereby present a case involving a 68-year-old female patient with an extraneural perineurioma (EPN) located on the mandibular region. A laser-assisted excisional biopsy was performed, and the diagnosis of EPN was confirmed through histopathological examination complemented by immunohistochemical analysis. The lesion was surgically excised, and no recurrence was observed during a one-year follow-up period. Accurate recognition of EPNs in the oral cavity is crucial to prevent unnecessary aggressive surgical interventions. Misdiagnoses may occur in cases of fibromas, neurofibromas, schwannomas, ossifying fibromas, or low-grade malignancies, which can potentially result in overtreatment that may compromise both function and aesthetics. Given the rarity of oral EPN, precise diagnosis and appropriate management are essential to avoid unwarranted invasive procedures and to mitigate potential medico-legal implications originating from misdiagnosis or suboptimal treatment. Ensuring comprehensive informed consent and meticulous documentation is also vital in minimizing medico-legal risks.

Extraneural perineuriomas are rare, benign soft tissue tumors arising from perineurial cells, which form the protective lining of peripheral nerves. These tumors are infrequently encountered in the foot, posing diagnostic challenges due to their rarity and non-specific clinical presentation. Here, we describe the case of a 45-year-old woman, who had a swelling over the right foot dorsum for four years for which an excision biopsy was done. Her histopathological variant and immunohistochemistry were consistent with extraneural perineurioma. This article aims to present a comprehensive review of extraneural perineuriomas, focusing on a case study involving the foot, and to discuss the clinical and histopathological characteristics, differential diagnosis, treatment options, and prognosis of this uncommon entity.

Pseudolipoblastic perineurioma is a very uncommon variant of extraneural perineurioma, with only a limited number of cases documented in the medical literature. The most remarkable histopathologic characteristic is the existence of vacuolated cells that closely resemble lipoblasts; besides the presence of small, spindle shaped, or epithelioid perineurial cells. In this study, we present another case of pseudolipoblastic perineurioma, predominantly characterized by the presence of vacuolated "pseudolipoblastic" cells. The immunohistochemical expression of EMA, Glut-1, claudin-1, collagen type IV, and laminin as well as S-100 negativity is essential for the diagnosis to support the perineurial origin. Simple excision is the best treatment option for these benign tumors that do not recur or metastasize. It is crucial to recognize this rare entity to differentiate it from many other tumors characterized by prominent intracytoplasmic vacuoles.

To examine the CT and MRI characteristics of extraneural perineuriomas. With IRB approval, our institutional imaging database was retrospectively reviewed for cases of pathologically proven extraneural perineuriomas. CT and MRI features were recorded, correlative imaging analyzed, and the electronic medical record cross-referenced. We identified ten patients [(seven males, three females, mean age 49.4 ± 18.3 years (range, 16-70 years)]. All cases were pathologically confirmed. Nine cases were conventional soft tissue extraneural perineuriomas, including one with "reticular" features and one with histologic features of malignancy; the tenth case contained admixed Schwann cells (hybrid perineurioma/schwannoma). Six out of ten patients underwent CT and ten of ten MRI evaluation. Nine out of ten MRIs were performed with IV contrast. Five lesions were subcutaneous, four intermuscular, and one intramuscular. Mean lesion diameter was 4.3 ± 2.7 cm (range, 0.9-10.2 cm). Nine out of ten lesions were well circumscribed; one had irregular margins. On CT, five of six were hypodense and one isodense compared to skeletal muscle. Most lesions were T1 isointense (5/10) or hypointense (4/10) and T2 hyperintense (7/10) relative to skeletal muscle, and demonstrated solid enhancement (6/9). There was no evidence of muscular denervation on any MRI exam, and a nerve of origin was identified in two out of ten cases. Extraneural perineuriomas have a distinctly different imaging appearance from intraneural perineuriomas, manifesting as rounded or ovoid soft tissue masses, without evidence of muscular denervation, and usually without an apparent nerve of origin. Because these features mimic other benign and malignant soft tissue lesions, including sarcomas, biopsy or excision is needed for definitive diagnosis.

Perineurioma is a relatively rare benign peripheral nerve sheath tumor composed of cells resembling to normal perineurium. Although this tumor may arise in the context of a nerve (intraneural perineurioma), extraneural perineurioma does occur, frequently involving the soft tissues of the lower and upper extremities, trunk and head and neck. Rarely it has also been reported in visceral organs, including gastrointestinal tract. We herein describe the clinicopathologic features of a rare case of a perineurioma presenting as a polypoid lesion of the sigmoid colon, emphasizing the pathologic diagnostic clues.