Plexiform schwannoma accounts for approximately 2%–5% of schwannoma. It often afflicts young adults, affecting males and females at a similar rate, and is most commonly located in the head, neck, trunk, or upper extremities. Plexiform schwannoma occasionally occur in the foot, but are rarely found in the lower limbs.1 The tumor usually presents as a solitary, slow-growing, asymptomatic nodule, and the maximum diameter of plexiform schwannomas is less than 2 cm.2 Trauma-related plexiform schwannoma is rare and needs to be differentiated in clinic. Herein, we report an unusual case of 28-year-old women with a reddish-brown plaque of her right thigh accompanying tenderness, the patient had been injured in the same location where the plaque later developed, and the histopathological results were consistent with plexiform schwannoma.
A 28-year-old female patient presented with a plaqueon on her right thigh for more than 10 years. Over a decade ago, the patient had noticed a nodule about the size of 1 cm on her right thigh. At that time, it was slightly tender, and enlarged slowly over the years. There were no similar lesions on other parts of her body. When she was 6 years old, the patient had been injured in the same location where the plaque later developed. There was no family history of plexiform schwannoma.
Dermatological examination showed presentation of tumor on the inside of the patient's right thigh as a medium-sized, reddish-brown plaque with a well-defined boundary (Fig. 1A). The lesion was 2 cm × 3 cm, with granular sensation. The lesion had slightly upheaved the skin surface, and was tender in response to palpation. A histopathological examination revealed irregular thickening of the epidermis spinous layer, increased pigment of the basal lamina, and multi-nodular well-defined tumor masses in the dermis and subcutaneous tissues. The masses were surrounded by a fibrous capsule and composed of spindle cells with hyperchromatic nuclei. Nuclear atypia was observed, but there were no pathological nuclear mitotic figures (Fig. 1B–1D). Immunohistochemical staining showed the following patterns: S-100 (+), Ki67 (< 1%+), EMA (focal+), vimentin (+), α-SMA (−), and NF (−) (Fig. 1E). Based on the above findings, a diagnosis of plexiform schwannoma was made. The patient refused to undergo surgical resection, so we advised follow-up for her in our out-patient clinic. By the writing time, there is no significant change in skin lesions during follow-up.
Plexiform schwannoma is a rare variant of schwann-oma, and there are fewer than ten case reports describing this tumor type in the lower limbs.3-7 Although trauma may play a role in the formation of schwannoma,1,8 the case of cutaneous plexiform schwannoma caused by trauma are rarely reported. Upon diagnosis, the skin lesion was more than 2 cm large. Histopathological examination showed multiple intradermal or subcutaneous nodules, mainly com-posed of cellular Antoni type A regions in which there were palisading nuclear and Verocay bodies. Immuno-histochemical staining revealed that S-100 protein and vimentin were detected diffusely, whereas desmin was not detected. Several cases of cutaneous plexiform schwannoma have been accompanied by neuro-fibromatosis type I, and a few cases may have been associated with neurofibromatosis type II, schwann-omatosis, or meningioma. The diagnosis of plexiform schwannoma needs to be made based on biopsy results, which can help to distinguish it from plexiform neurofibroma, plexiform fibrous histio-cytoma, and nerve sheath myxoma.
In conclusion, plexiform schwannoma is a benign peri-pheral nerve sheath tumor particularly associated with neurofibromatosis, and the prevalence of recurring tumors after their complete removal is rare (2%). The histopathological and immunohistochemical findings of this patient provided conclusive evidence for a diagnosis of solitary plexiform schwannoma, and our case was associated with the history of local trauma. The case helps to improve the understanding of plexiform Schwannoma.
. Li XN, Cui JL, Christopasak SP, et al Multipleplexiform schwannomas in the plantar aspect of the foot: case report and literature review. BMC MusculoskeletDisord 2014;15:342. doi:10.1186/1471-2474-15-342.
. Nishio J, Mori S, Nabeshima K, et al Successful enucleation of large multinodular/plexiforms schwannoma of the foot and ankle. Springer plus 2015;4:260. doi:10.1186/s40064-015-1087-3.
. Shishiba T, Niimura M, Ohtsuka F, et al Multiple cutaneous neurilemmomas as a skin manifestation of neurilemmomatosis. J Am Acad Dermatol 1984;10(5 Pt 1):744–754.
. Kao GF, Laskin WB, Olsen TG. Solitary cutaneous plexiform neurilemmoma (schwannoma): a clinicopathologic, immunohisto-chemical, and ultrastructural study of 11 cases. Mod Pathol 1989;2(1):20–26.
. Ko JY, Kim JE, Kim YH, et al Cutaneous plexiform schwann-omas in a patient with neurofibromatosis type 2. Ann Dermatol 2009;21(4):402–405. doi:10.5021/ad.2009.21.4.402.
. Kim WI, Kim TW, Park SM, et al Plexiform schwannoma with localized hypertrichosis. Ann Dermatol 2018;30(4):508–509. doi:10.5021/ad.2018.30.4.508.
. Woodruff JM, Scheithauer BW, Kurtkaya-Yapicier O, et al Congenital and childhood plexiform (multinodular) cellular schwannoma: a troublesome mimic of malignant peripheral nerve sheath tumor. Am J Surg Pathol 2003;27(10):1321–1329.
. Jacobson JM, Felder JM, Pedroso F, et al Plexiform schwannoma of the foot: a review of the literature and case report. J Foot Ankle Surg 2011;50(1):68–73. doi:10.1053/j.jfas.2010.07.002.