Malignant Peripheral Nerve Sheath Tumour (MPNST) of the Prostate Gland: A Review and Update
Authors: Kodzo-Grey Venyo Anthony 
Published: July 2024

Even though adenocarcinoma of the prostate gland is the commonest malignant tumour of the prostate gland that is encountered in all countries globally, other rare tumours of the prostate gland do exist and because of their rarity most clinicians would not have ever encountered such rare tumours during their training and their practices. Serum prostate specific antigen tests tend to be undertaken globally in screening for early detection of adenocarcinoma of the prostate gland globally because most adenocarcinomas of the prostate gland tend to be associated with high serum prostate specific antigens in comparison with lower serum PSA levels that tend to be found in majority of individuals of the same age group who do not have adenocarcinoma of the prostate gland. Malignant peripheral nerve sheath tumour (MPNST) of the prostate gland is a rare malignant that tends to be sporadically diagnosed and quite often the tumour to be diagnosed at an advanced stage or locally advanced stage as well as the tumour has tended to portend an aggressive biological behaviour and poor prognosis. MPNST can be diagnosed in some patients who are younger than the ages of individual adenocarcinomas but the tumour can also be found in individuals whose ages are similar to ages of individuals who have adenocarcinoma of the prostate gland. MPNST may be diagnosed incidentally in some individuals who do not have any symptoms, and they can also be diagnosed in individuals who have lower urinary tract symptoms of recent onset that is progressive, and they could also manifest with urinary tract infections, retention of urine, or symptoms related to their metastases or obstruction of the ureter or difficulty in opening their bowels. The serum PSA of patients who have MPNST tends to be low even if digital rectal examination of the patients, have demonstrated features of an abnormal prostate mass that could be firm or nodular or large and in individuals who have radiology image evidence of metastases from MPNST also tend to have low serum PSA levels but the serum PSA level could be raised when there is a contemporaneous synchronous adenocarcinoma associated with the MPNST. Radiology images that have tended to be used in assessing the prostate gland of individuals who have MPNST in various parts of the word including developing countries include: trans-rectal ultrasound scan of the prostate gland, Computed tomography (CT) scan of the prostate, magnetic resonance imaging (MRI) scan of the prostate gland. Diagnosis of MPNST tends to be made sporadically, in association with neurofibromatosis or pursuant to radiotherapy. Diagnosis of MPNST is made based upon the pathology examination features of prostate biopsies. Gross examination of specimens of MPNSTs had tended to demonstrate the ensuing features: Fusiform to globoid, pseudo-encapsulated tumour which often tend to be associated with gross evidence of necrosis. If the MPNST tumour is found to be arising from a nerve, an attached medium or large nerve tends to be evident upon gross examination. The frozen section examination features of MPNST had tended to demonstrate the following features: With regard to high grade tumours, overt features of malignancy tend to be readily found, including nuclear pleomorphism, brisk mitotic activity as well as areas of geographic necrosis; The diagnosis of low-grade MPNST lesions have tended to be difficult in frozen section examinations of the tumours. With regard to NF1, mitotic activity, increased cellularity and nuclear atypia within a neurofibroma do raise concern for the diagnosis of MPNST. Histopathology examination of specimens of MPNST have been summated to include the following: Upon low power microscopy pathology examination of MPNST, marbled appearance tends to be seen due to alternating hypocellular and hypercellular areas with perivascular accentuation tend to be seen; Uniform spindle cells with hyperchromatic, thin, wavy, or focally buckled nuclei tend to be seen; MPNST, could have uniform cellularity with fibrosarcoma-like fascicular growth, which would raise the differential diagnosis of synovial sarcoma; Specimens of MPNST could have foci of myxoid stroma and hyalinization; Epithelioid morphology can be seen upon microscopy examination in cases of MPNST, In MPNST specimens, precursor lesion, such as neurofibroma, could be identifiable; In cases of MPNST, Nuclear palisading tends to be uncommon; In cases of MPSNT, heterologous differentiation could be visualized upon microscopy examination of the specimen which might include chondrosarcomatous, osteosarcomatous and rhabdomyosarcomatous components (malignant triton tumour). With regard to the immunohistochemistry staining features of MPNST, It has been stated that specimens of MPNST tend on immunohistochemistry staining studies to exhibit positive staining for the ensuing tumour markers with the following features; Upon immunohistochemistry staining of MPNST specimens for S100 and SOX10, the specimens usually tend to exhibit patchy or focal and only seen in up to 50% of cases; Immunohistochemistry staining studies of MPNST specimens tend to exhibit positive staining for Desmin, myogenin, as well as MyoD1 within the rhabdomyosarcomatous elements of the MPNST. There is no consensus opinion on the treatment of MPNST, however, it has been stated that with regard to the treatment of MPNST, an aggressive surgical resection which is ensued by radiotherapy to achieve local control is the treatment of choice. It had also been pointed out that treatment options for the management of metastatic MPNST are limited; as well as that conventional chemotherapy had usually been limited to patients who have metastatic disease. Considering the MPNT of the prostate gland is an aggressive tumour and the fact that serum PSA levels tend to be low in such tumours, a high index of suspicion is required to establish early diagnosis of MPNST at a lower stage by undertaking thorough assessment of all patients who manifest with severe lower urinary tract symptoms with benign, firm prostates and low serum PSAs by undertaking radiology image biopsies of the prostates early whilst treating them with medications including tamsulosin to reassure patients they have benign disease or MPNST of the prostate gland or a different type of prostate cancer. A global multi-centre trial of radical prostatectomy with complete excision of the tumour plus a combination of radiotherapy and chemotherapy for localized tumours would be recommended as well as a global multi-centre trial of various combination chemotherapy options would be required for the treatment of metastatic MPNSTs as well as development of new effective chemotherapy medications would be recommended for the treatment of MPNSTs of the prostate gland.