Plexiform perineurioma of the lip: A case report and review of literature

Abstract

We describe a plexiform perineurioma, which is an extremely rare variant of soft tissue perineurioma. A 43-year-old Japanese man presented with a painless, well-demarcated, elastic, soft tumor measuring 2.0 × 1.9 cm on the upper lip that had persisted for three years. Microscopically, a plexiform tumor composed of minimally atypical spindle cells with wavy nuclei was located in the lamina propria of the oral mucosa. Tumor cells were concentrically arranged around small vessels and aligned in parallel with delicate collagen fibers on a fibromyxoid background in the hypocellular area. Tumor cells were immunohistochemically positive for EMA, GLUT-1, claudin-1, and CD34 and negative for S-100 protein. The histopathological and immunohistochemical profiles of the excised tumor indicated a diagnosis of plexiform perineurioma. The patient has remained free of recurrence for sixteen months. Intraoral soft tissue perineurioma is rare and two of the four reported plexiform perineuriomas, including that described herein, notably involved the intraoral area. According to previous reports, plexiform perineuriomas largely develop in middle-aged women without a history of type 1 or type 2 neurofibromatosis. The clinical courses of all reported plexiform perineuriomas have been benign.

On Pseudo-Onion Bulb Intraneural Proliferations of the Non-Major Nerves of the Oral Mucosa

“…The literature contains also rare examples of what their authors referred to as plexiform perineuriomas [27][28][29][30], two of them occurring on the lips, upper and lower, respectively. These peculiar tumors are classified as subtypes of STP since they reveal histopathologic features encountered in STP.…”

Perineurioma of the sciatic nerve with reticular, microcystic, and pseudolipoblastic features: illustrative case

“…Extraneural perineuriomas are most commonly well-circumscribed masses composed of bland spindle cells with elongated, overlapping processes arranged in storiform patterns and fascicles and typically present to clinical attention as painless superficial masses in midadulthood. [5][6][7] However, more recently in the literature, new variants of perineurioma based on histology-sclerosing, [8][9][10][11] plexiform, [12][13][14] granular, 15 epithelioid, 16 reticular/ microcystic, 17,18 pseudolipoblastic 19 -have also been described. The pseudolipoblastic perineurioma is a rare soft tissue variant that may mimic liposarcoma and is characterized by epithelioid perineurial cells with abundant clear intracytoplasmic vacuoles.…”