Vaginal Malignant Peripheral Nerve Sheath Tumor ( MPNST ) With Unusual Liposarcomatous Differentiation-A Case Report

C l i n M e d International Library Citation: Gougeon F, Doyon J, Sauthier P, Rahimi K (2015) Vaginal Malignant Peripheral Nerve Sheath Tumor (MPNST) With Unusual Liposarcomatous Differentiation A Case Report. Int J Cancer Clin Res 2:030 Received: September 25, 2015: Accepted: October 26, 2015: Published: October 28, 2015 Copyright: © 2015 Gougeon F. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Gougeon et al. Int J Cancer Clin Res 2015, 2:4


Pathology
Microscopic evaluation revealed an ulcerated lesion consisting of spindled and epithelioid neoplastic cells with marked atypia, pleomorphism and high mitotic activity (20-25/10 hpf) .Irregularly shaped vessels of various sizes were unevenly distributed throughout the lesion.The malignant cells showed hyperchromatic nuclei with one to three prominent eosinophilic nucleoli and vacuolated amphophilic to eosinophilic cytoplasm (Figure 1).Some cells showed optically clear vacuoles that sometimes pushed the nuclei to the periphery.These vacuoles were not stained by Alcian blue or hyaluronidase.These cells appeared frankly neoplastic (Figure 2).

Introduction
Malignant peripheral nerve sheath tumors (MPNST) are neoplasms that arise from a peripheral nerve or, when situated in extra-neural soft tissue, that show nerve sheath differentiation.They account for about 5 -10% of soft tissue sarcomas and are strongly associated with neurofibromatosis type I.Most of these tumors arise either from a preexistent neurofibroma or de novo from nerve sheath.The most frequent locations are the large and medium nerves of the buttock and thighs or brachial plexus.A small minority arises from extra-neural soft tissue [1].
Approximately 15% of MPNSTs show divergent histological differentiation, either mesenchymal or epithelial.Divergent mesenchymal differentiation usually consists of cartilage, skeletal muscle or bone.We are aware of only three reported cases of MPNST which presented liposarcomatous differentiation [2][3][4].
Although MPNSTs have been reported in many locations unrelated to major nerve trunks, there is, to date, only two cases of vaginal MPNST reported in the literature [5,6].

Clinical
The patient is a 70 y.o.women of French-Canadian ancestry in good general health.There was no personal or family history of neurofibromatosis.

ISSN: 2378-3419
O'Sullivan.Int J Cancer Clin Res 2015, 2:4 peripheral nerves or showing nerve sheath differentiation (excluding tumors arising from the peripheral nerve vasculature or epineurieum) [7] They represent about 5 -10% of soft tissue sarcomas [1].They are very aggressive tumors, frequently showing early haematogenous dissemination [8].Most of these tumors are high grade and measure more than 5 cm at the time of diagnosis.They are associated with neurofibromatosis type 1 in about a third of patients.The 5-year survival rate for treated patients has historically been reported to be less than 50% but seems to have improved in recent years due to improved surgical techniques and liberal use of neo-adjuvant treatments [8,9].
Pathologically, although there is good agreement on diagnosis for MPNSTs arising from benign neural tumors or de-novo from nerve bundles, there is more discordance for tumors arising sporadically in other locations.The major histological criteria are: 1) The presence of dense and hypodense fascicles alternating in a marbled appearance 2) Asymmetrically tapered spindle cells with irregular buckled nuclei and 3) Schwann cell differentiation by immunohistochemistry or electron microscopy in a sarcomatous tumor.Other weaker criteria include nuclear palisading, whorled structures and hyperplastic vascular changes [10].
Our case is unusual because of its location and because of the liposarcomatous differentiation.Although a small number of cases have been reported in the uterine cervix and vulva, we are aware of only two reported cases of vaginal MPNST [5,6,11,12].
A recent retrospective series of 175 cases showed that the most frequent localizations of MPNSTs are the extremities (45%) followed by the trunk (34%) and head and neck region (19%) [7].They usually arise from large or medium nerve trunks or pre-existing neurofibromas [13].Unusual localizations of MPNSTs that have been reported include the kidney, the oral cavity, the eyelids and the heart [14][15][16][17].

Discussion
MPNSTs are defined as malignant neoplasms derived from  Embryonal rhabdomyosarcomas occur mainly in children.Most of the patients with vaginal sarcomas present with vaginal discharge or palpable mass [18].
Divergent differentiation is a well-known phenomenon in MPNSTs.A review of the histological characteristics of 120 cases showed this occurred in about 16% of MPNSTs [8].Rhabdomyoblastic, osteoblastic, chondroblastic and glandular differentiation have been described.Three cases of liposarcomatous differentiation have been reported [2][3][4].A few cases of benign adipocyte differentiation have been reported in benign nerve sheath tumors [19].It is important not to mistake benign adipocytes entrapped by the tumor asliposarcomatous differentiation.The cells showing liposarcomatous differentiation should have atypical pleomorphic nuclei, as opposed to those of entrapped adipocytes.In our case, the adipocytes showed frank atypia, and were thus considered malignant.This type of divergent differentiation can also raise the possibility of a de-differentiated liposarcoma, but the de-differentiated component of liposarcomas is usually high-grade "malignant fibrous histiocytoma-like", which was not the case here [2].Furthermore, de-differentiated liposarcomas usually have positive staining for MDM-2 and CDK-4 [20].
The differential diagnostic in this case also included other types of sarcomas (leiomyosarcoma, fibrosarcoma) and spindle cell melanoma.Other sarcomas were ruled out mainly by immunochemistry.The lack of expression of myogenic markers (desmin, caldesmon) and cytokeratins argued against a diagnosis of leiomyosarcoma or synovial sarcoma, respectively.The histological appearance would also have been highly atypical for synovial sarcoma.De-differentiated liposarcoma was ruled-out on the basis of negative staining for MDM-2 and CDK-4.Malignant melanoma was ruled-out on the basis of negative melanocytic markers other than S-100 (HMB45, Melan-A, Mart-1).

Conclusion
In summary, we present here a case of vaginal MPNST, epithelioid type, with liposarcomatous differentiation.A review of the literature shows that these tumors are extremely rare in the female genital tract.It is a reminder that these tumors can arise at various locations beside major nerve trunks.Liposarcomatous differentiation has been described in very few cases, although MPNSTs are notorious for having divergent differentiation, usually rhabdomyosarcomatous or osteoblastic.