Cytomorphology of metastatic malignant peripheral nerve sheath tumour present in pleural fluid: Case study and literature review

The cytomorphology of MPNST in effusion specimens is rarely described. In this paper, the detailed cytopathological and immunohistochemical characteristics of metastatic MPNST has been described in pleural effusion. Patients' medical history and the judicious utilization of ancillary studies contribute to ensure precise cytological diagnoses. The cytomorphology of malignant peripheral nerve sheath tumour (MPNST) in effusion specimens can be diagnostically challenging. The author presents detailed cytopathological and immunohistochemical characteristics of a case of metastatic MPNST in pleural effusion.

An algorithmic approach to the management of peripheral nerve tumours

This article reviews the pathology and management of peripheral nerve tumours, including a framework for investigation and decision-making. Most tumours are benign, including schwannomas and neurofibromas, but malignant peripheral nerve sheath tumours can occur. The risk of malignant change is remote for schwannomas but higher for neurofibromas, particularly in neurofibromatosis type 1. Magnetic resonance imaging is useful for defining the relationship of a swelling with adjacent nerves but is not definitive for tissue diagnosis. Increasing size, pain and neurological deficit suggest malignant change and TruCut needle biopsy is indicated, although there is a risk of sampling error. Excision biopsy preserving nerve function may be carried out for benign tumours to relieve symptoms. Malignant tumours require a multidisciplinary approach. Complete surgical excision with clear margins is the only curative treatment and may be supplemented with radiotherapy and chemotherapy. However, prognosis remains poor, particularly for patients with neurofibromatosis.

PRAME expression in spindle cell melanoma, malignant peripheral nerve sheath tumour, and other cutaneous sarcomatoid neoplasms: a comparative analysis

Diagnosis of spindle cell/sarcomatoid melanoma may be challenging due to frequent loss of expression of melanocytic marker(s) and histomorphologic resemblance to various mesenchymal tumours, particularly malignant peripheral nerve sheath tumour (MPNST). Overexpression of PReferentially expressed Antigen in MElanoma (PRAME) supports a diagnosis of melanoma when evaluating challenging melanocytic tumours. PRAME expression in MPNST and other cutaneous sarcomatoid neoplasms, however, has not been well characterised. We aimed to determine the utility of PRAME immunostain in distinguishing spindle cell melanoma from MPNST and other sarcomatoid mimics. PRAME expression was scored by extent (0 to 4+) and intensity (0 to 3) of staining. A strong positive correlation was observed between the extent and intensity scores (r = 0.84). An extent score of 4+, defined by staining in 76-100% of tumour cells, was seen in 56% (23/41) of spindle cell melanomas, 18% (7/38) of MPNSTs, 15% (4/27) of cutaneous sarcomatoid squamous cell carcinomas (SCCs), 33% (5/15) of poorly differentiated cutaneous angiosarcomas, 12% (4/33) of atypical fibroxanthomas (AFXs), 4% (1/25) of pleomorphic dermal sarcomas (PDSs), and none (0/16) of the high-grade cutaneous leiomyosarcomas. A significant difference was found between spindle cell melanoma and all other examined sarcomatoid neoplasms except angiosarcoma. While diffuse (and often strong) PRAME expression is more frequently observed in spindle cell melanoma than MPNST, sarcomatoid SCC, AFX, PDS, and high-grade leiomyosarcoma, its limited sensitivity and specificity caution against its use as a standalone diagnostic marker. PRAME may complement other epigenetic or lineage-specific markers and should only be used as part of an immunohistochemical panel when evaluating these sarcomatoid neoplasms.

Primary Intraosseous Malignant Peripheral Nerve Sheath Tumor of the Humerus: Report of a Rare Case

Malignant peripheral nerve sheath tumors (MPNSTs) usually arise in the soft tissues. Intraosseous MPNSTs are rare. They may arise de novo but are typically associated with neurofibromatosis type 1 (NF1) and radiation therapy. Our patient is a 58-year-old female patient that presented with right shoulder pain. An MRI showed a shoulder mass, and percutaneous bone biopsy demonstrated morphology suggestive of an MPNST; besides, on immunohistochemistry, SOX10 was positive, and H3K27me3 expression was entirely lost. The patient underwent total resection of the right proximal humerus and endoprosthetic shoulder reconstruction, followed by radiation therapy and chemotherapy. Only a few cases in the mandible, spine, maxilla, ulna, metacarpal, tarsal, and one in the humerus have been published. In this paper, we contribute with an additional case of primary intraosseous MPNST in the humerus and a brief literature review.

CDX2 expression in malignant peripheral nerve sheath tumour: a potential diagnostic pitfall associated with PRC2 inactivation

AIMS

Malignant peripheral nerve sheath tumour (MPNST) is a soft tissue sarcoma that exhibits features of Schwann cell differentiation. Heterologous, often mesenchymal-type differentiation occurs in a subset of MPNST, while glandular morphology also is encountered in rare cases. We observed in MPNST unanticipated expression of CDX2, a transcription factor that regulates intestinal epithelial differentiation, and aimed to further characterize this phenomenon.

METHODS/RESULTS

Expression of CDX2 was assessed by immunohistochemistry in a total of 32 high-grade MPNSTs lacking morphological evidence of epithelial differentiation, including twelve tumours (38%) that developed in the setting of neurofibromatosis and four (13%) in the setting of prior radiation therapy. CDX2 was expressed by 14 of 32 MPNSTs (44%), wherein immunoreactivity, varying from weak to strong, was present in 2-95% of neoplastic spindle cells (median 10%, mean 23%). Notably, CDX2 expression was limited to tumours with PRC2 inactivation (22/32; 69%), as evidenced immunohistochemically by diffuse loss of trimethylated histone H3K27. Analysing publicly available RNA-sequencing data from twelve MPNST cell lines, two of which are clonally related, we observed CDX2 expression in all six PRC2-inactivated cell lines, while CDX2 expression was negligible in six cell lines with intact PRC2, amounting to a 58-fold increase in CDX2 expression on average with PRC2 inactivation.

CONCLUSIONS

CDX2 is expressed in a subset of MPNSTs, even in the absence of morphological evidence of epithelial differentiation. CDX2 expression in MPNST is strongly associated with underlying PRC2 inactivation.

Malignant Peripheral Nerve Sheath Tumor Presenting as Horner's Syndrome

Malignant peripheral nerve sheath tumor (MPNST) is a rare, aggressive sarcomatous tumor that arises from peripheral nerve sheath and shows Schwann cell differentiation. They are commonly seen among cases with existing benign plexiform neurofibromas, prior radiation treatment, and large germline mutations involving the entire neurofibromatosis 1 (NF1) gene. MPNST can have varied presentations; hence diagnosis remains a great challenge. Here we report a rare case of MPNST in an NF1 patient who presented with Horner´s syndrome. A young male reported swelling in the neck, dyspnea on exertion, and dysphagia. Subsequently, he was diagnosed to have a malignant peripheral nerve sheath tumor arising from the mediastinum and compressing the ipsilateral cervical sympathetic plexus causing Horner′s syndrome. The patient underwent surgical resection of the mediastinal mass followed by chemotherapy. His symptoms improved significantly following treatment. This case report emphasizes the fact that high suspicion of MPNST is required when NF1 cases present with mass lesions, so that early surgical clearance with chemoradiation may offer a near-complete cure.

Malignant peripheral nerve sheath tumour of the oral and maxillofacial region-A systematic review

To integrate the available data published on malignant peripheral nerve sheath tumours (MPNST) of the oral and maxillofacial region. Searches in Embase, PubMed, Web of Science and Scopus were conducted for the identification of case reports/case series in English language. The risk of bias was assessed using the Joanna Briggs Institute tool. Outcomes were evaluated by Cox regression and Kaplan-Meier methods. A total of 306 articles were retrieved, 50 of which reporting 57 MPNST were included. The lesion showed a predilection for the mandible (n = 18/31.57%) of middle-aged adults (~40.5 years) with a male/female ratio of 1.1:1. The individuals were mostly symptomatic with a mean evolution time of 9.6 months. Surgical removal plus adjuvant therapy (especially radiotherapy) was the main approach (51.86%). Recurrence was reported in 39.62% of cases. Nodal and distant metastases were identified in 28.26% and 26.66% of cases, respectively. The 2-year cumulative survival rate was 55%. Independent predictors of poor survival were the presence of neurofibromatosis type 1 (p = 0.04) and distant metastases (p = 0.004). The diagnosis of MPNST is challenging due to the variety of its clinical and histopathological presentations. Local aggressiveness and the potential for metastases are common outcomes of this neoplasm.

Malignant Peripheral Nerve Sheath Tumour of the Forearm Presenting as Foreign Body

Malignant peripheral nerve sheath tumour (MPNST) is a rare form of soft tissue sarcoma that arises from peripheral nerves, accounting for less than 5% of cases. MPNST most commonly affects trunk and extremities, and It is commonly associated with neurofibromatosis type 1 (NF1) (40%-50%). We present a case of MPNST in a 52-year-old man with history of well-controlled epilepsy. He presented with a painful and erythematous mass in his left forearm, which was initially diagnosed as an abscess secondary to retained foreign bodies. Despite incision and drainage, he experienced recurrence of this mass two months later. Subsequent debridement, biopsy and histology revealed a high-grade MPNST. This prompted a referral to the regional sarcoma unit. Unfortunately, repeat scans demonstrated rapid progression of disease into the anterior forearm compartment and bony invasion. Despite radiotherapy, the tumour metastasised to his lungs. After undergoing palliative chemotherapy, unfortunately, the patient survived only 14 months from the initial presentation. Our study affirms that all resected tissues should be sent for histological confirmation of the suspected diagnosis. When intraoperative findings do not correlate with the initial presentation, the clinician should have a high index of suspicion for potential malignancy. Finally, it is essential that all patients with soft tissue sarcoma should be referred to the specialist regional soft tissue sarcoma service, to be managed by a specialist sarcoma multidisciplinary team according to guidelines.

Malignant Peripheral Nerve Sheath Tumour in a Seba's Short-Tailed Bat (Carollia perspicillata)

There are few reports of tumours in bats, despite the fact that members of the Chiroptera order include 22.4% of all currently known mammal species. We now describe a case of malignant peripheral nerve sheath tumour (MPNST) in an adult female Seba's short-tailed bat (Carollia perspicillata) from a private zoo in Switzerland. The macroscopical and histological findings indicated that the MPNST originated from a dorsal spinal nerve root sheath in the lumbar region and metastasized to the spleen. Immunohistochemical labelling for glial fibrillary acid protein, S100 protein, neuron specific enolase and synaptophysin was negative. The cytoplasm of a few neoplastic cells labelled for smooth muscle actin and desmin. To our knowledge, this is the first report of a PNST in a member of the Chiroptera order.

Rapidly Growing Huge Lower Back Malignant Peripheral Nerve Sheath Tumour

Malignant peripheral nerve sheath tumours (also called neurofibrosarcomas) are a rare, highly aggressive soft tissue sarcomas that arise from the peripheral nerves or cells associated with the nerve sheath, such as Schwann cells, peri-neural cells and fibroblasts. It is representing 10% of all soft tissue sarcomas in which it is considered as an extremely rare malignancy, especially in patients with neurofibromatosis type I. In the general population, it affects approximately 1 in 100,000 people. This article is reporting a 56-year-old Malay female patient who is a known case of neurofibromatosis type I for 20 years, presented with a lower back, pruritic, gradually increasing swelling during the last five months. Last month before the presentation, the lesion rapidly grows, reaching a size of (15×15 cm), accompanied by foul-smelling discharge and pain exacerbated with movement. Although no history of preceding trauma or accident, the mass bleeds within contact. In conclusion, only a few cases of giant malignant peripheral nerve sheath tumours reported in the literature describing its location and growth progression. We present a massive, extremely rapid growth of cutaneous exophytic malignant peripheral nerve sheath tumours over the lower back.

A Rare Case of Epithelioid Malignant Peripheral Nerve Sheath Tumor Mimicking Malignant Melanoma

Malignant peripheral nerve sheath tumors are rare soft tissue sarcomas that are often associated with neurofibromatosis type-1. These tumors share common immunohistochemistry findings which can make diagnosis difficult. We present the case of a woman who presented with a diagnosis of metastatic melanoma of the index finger of her left hand but was eventually diagnosed with primary epithelioid malignant peripheral nerve sheath tumor. We will be highlighting the diagnostic challenge of differentiating between these two very different malignancies.

Composite phaeochromocytoma with malignant peripheral nerve sheath tumour: A case report with summary of prior published cases

Composite phaeochromocytomas (CP) are extremely uncommon adrenal medullary tumours where phaeochromocytoma coexists with another adrenal medullary tumour also of neural crest origin. CP includes combination of phaeochromocytoma along with a component of neuroblastoma, ganglioneuroblastoma, ganglioneuroma, benign nerve sheath tumour or a malignant peripheral nerve sheath tumour (MPNST). Here we describe the morphological and immunohistochemical details of a case of CP with MPNST in a 30 years old lady, without history of neurofibromatosis. Only 6 cases of CP with MPNST have been reported so far. We have tabulated a summary of these prior published cases of phaeochromocytoma with MPNST. To our knowledge, this is the first literature review describing the clinico-pathological characteristics of these rare tumours.

Giant intrapulmonary malignant peripheral nerve sheath tumour

Pulmonary malignant peripheral nerve sheath tumours (MPNSTs) are extremely rare soft tissue sarcomas that develop from the cell constituting the nerve sheaths, approximately 5-10% of all soft tissue sarcomas. We present a rare case of primary lung MPNST in an adult female non-smoker patient, in whom surgical thoracotomy approach has obtained a good control of the disease. Low-grade MPNST was established from excisional biopsy followed by immunohistochemistry.

Malignant peripheral nerve sheath tumours in magnetic resonance imaging: primary and recurrent tumour appearance, post-treatment changes, and metastases

PURPOSE

To analyse the appearance of primary and recurrent malignant peripheral nerve sheath tumours (MPNSTs) in magnetic resonance imaging (MRI) with a focus on configuration, and to assess the occurrence of loco-regional post-treatment changes and metastases during post-treatment follow-up.

MATERIAL AND METHODS

Twenty patients with histologically proven MPNST underwent post-treatment 1.5 T MRI. Primary and recurrent MPNSTs were examined for configuration, contrast enhancement, extent, and signal intensity in MRI. Loco-regional post-treatment changes and information on metastases were extracted from the follow-up.

RESULTS

MPNSTs occurred most often in the extremities (p = 0.006). Twenty per cent (n = 4) of the patients developed recurrences, with a total of 24 lesions. Recurrent MPNSTs were significantly smaller than primary MPNSTs (p = 0.003). Primary MPNSTs mostly occurred unifocally as multilobulated or ovoid and heterogeneous lesions with mostly well-defined borders. Recurrent MPNSTs purely occurred multifocally as mostly nodular (p < 0.001), multilobulated, or ovoid lesions. 80%, 65% and 30% of the patients showed post-treatment subcutaneous oedema (p = 0.002 to 0.03), muscle oedema (p = 0.02), and seroma, respectively. Twenty-five per cent (n = 5) of patients presented metastases during follow-up. The relative risk in patients with recurrences to develop lung or lymph node metastases is eightfold (p = 0.056).

CONCLUSIONS

While primary MPNSTs mostly appear unifocally as multilobulated or ovoid lesions, recurrent MPNSTs purely occur multifocally as mostly nodular lesions. Subcutaneous and muscle oedema are very common loco-regional post-treatment changes. Patients with recurrences have a higher risk for lung and lymph node metastases.

Neurofibromatosis type 1-associated malignant peripheral nerve sheath tumour carcinomatous pleurisy: an autopsy case

A 57-year-old man with neurofibromatosis type 1 (NF-1) and intrathoracic meningoceles was admitted to hospital after presenting with neck pain and progressive dyspnoea. On admission, a chest computed tomography scan demonstrated right pleural effusion, neck tumour, intrathoracic meningoceles, and rib metastasis. The myelography showed no transportation between the intrathoracic meningoceles and pleural cavity. As a result, these radiological finding indicated the potential for malignant transformation. The appearance of the right pleural effusion was bloody and had no malignant cells. We biopsied the neck tumour, and the tissue showed glass-like materials but no malignant cells. At 1 month after admission, he developed bladder-rectal disorder, syndrome of inappropriate secretion of antidiuretic hormone, and paralysis of both legs and later died. An autopsy demonstrated glass-like material in the neck tumour, which was surrounded by malignant cells. NF-1 appears to have progressed to a malignant peripheral nerve sheath tumour in this patient.

Malignant peripheral nerve sheath tumor of the nasal cavity and nasopharynx in a child: A case report

RATIONALE

Malignant peripheral nerve sheath tumors (MPNSTs) are rare neoplasms with only a few reported cases affecting the nasal cavity, paranasal sinuses, and anterior skull base.

PATIENT CONCERNS

A 12-year-old girl with a mass in her nose was admitted to the Department of Otorhinolaryngology of Shenzhen Children's Hospital. She had a 4-month history of progressive, unilateral right nasal obstruction, unilateral mucopurulent rhinorrhea, foul nasal odor, snoring, hyposmia, occasional epistaxis, and no headache, no facial numbness, without eye swelling and vision loss.

DIAGNOSE

A computed tomography (CT) scan of the paranasal sinuses showed a mass (right inflammatory polyp and calcification) involving the nasal cavity, the right maxillary sinusitis, ethmoid sinusitis. There was no nasal septum, orbital, or skull base involvement. On the basis of pathological and immunohistological findings, the tumor was diagnosed as an MPNST with heterogeneous components (cartilage and bone) mesenchymal differentiation after the operation.

INTERVENTIONS

The girl was treated by surgery and chemotherapy.

OUTCOMES

The postoperative course was uneventful. There was no recurrence observed during the 3-year follow-up.

LESSONS

The primary MPNST in the nasal cavity is rare, if nasal neoplasms do not respond well to vasoconstrictors and glucocorticoids in children, the possibility of a tumor should be considered. If new organisms grow rapidly with hemorrhagic necrosis, the possibility of a malignant tumor is greater.

Evaluation of eight melanocytic and neural crest-associated markers in a well-characterised series of 124 malignant peripheral nerve sheath tumours (MPNST): useful to distinguish MPNST from melanoma?

AIMS

The diagnosis of malignant peripheral nerve sheath tumour (MPNST) may be challenging, especially in the sporadic setting. Owing to the lack of specific histological criteria, immunohistochemical and molecular diagnostic markers, several differential diagnoses must be considered, especially melanoma. Indeed, although S100 protein usually stains melanoma, other melanocytic markers are often negative, especially in spindle cell/desmoplastic types. This pattern of immunoreactivity resembles that of some nerve-derived tumours such as MPNST. Owing to their different clinical behaviours and therapeutic implications, accurate identification of these two different tumours is crucial.

METHODS AND RESULTS

S100, SOX10, KBA62, MITF, HMB45, Melan-A, tyrosinase PNL2 and BRAF-V600E immunostaining was performed in a pathologically and genetically well-characterised cohort of primary MPNST (n = 124), including 66 (53%) NF1-associated tumours. Sox10 and KBA62 expression were found, respectively, in 102 (84%) and in 101 (83%) MPNST, whereas S100 was expressed in 64 cases (52%). We observed an increased loss of S100 with increasing histological grade (P = 0.0052). We found Melan-A expression in 14% (n = 17) of all MPNST, occurring in 82% (n = 14) of cases in an NF1 context. Six per cent (n = 8) of MPNST showed tyrosinase positivity, including seven (87%) NF1-associated. MITF expression was found in 10 (8%) MPNST. None expressed PNL2, HMB45 or BRAF-V600E.

CONCLUSION

MPNST (in NF1 and a sporadic setting) can quite often be positive for Melan-A, tyrosinase and MITF. Pathologists should be cognisant of these exceptions to prevent confusion with melanoma.

Monitoring of plexiform neurofibroma in children and adolescents with neurofibromatosis type 1 by [18 F]FDG-PET imaging. Is it of value in asymptomatic patients?

PURPOSE

About 10% of patients with neurofibromatosis type 1 (NF-1) develop malignant peripheral nerve sheath tumours (MPNST) mostly arising in plexiform neurofibroma (PN); 15% of MPNST arise in children and adolescents. 2-[¹⁸ F]fluoro-2-deoxy-d-glucose ([¹⁸ F]FDG)-PET (where PET is positron emission tomography) is a sensitive method in differentiating PN and MPNST in symptomatic patients with NF-1. This study assesses the value of [¹⁸ F]FDG-PET imaging in detecting malignant transformation in symptomatic and asymptomatic children with PN.

METHODS

Forty-one patients with NF-1 and extensive PN underwent prospective [¹⁸ F]FDG imaging from 2003 to 2014. Thirty-two of the patients were asymptomatic. PET data, together with histological results and clinical course were re-evaluated retrospectively. Maximum standardised uptake values (SUVmax) and lesion-to-liver ratio were assessed.

RESULTS

A total of 104 examinations were performed. Mean age at first PET was 13.5 years (2.6-22.6). Eight patients had at least one malignant lesion; four of these patients were asymptomatic. Two of four symptomatic patients died, while all patients with asymptomatic malignant lesions are alive. All malignant tumours could be identified by PET imaging in both symptomatic and asymptomatic patients. All lesions judged as benign by [¹⁸ F]FDG imaging and clinical judgment were either histologically benign if removed or remained clinically silent during follow-up. SUVmax of malignant and benign lesions overlapped, but no malignant lesion showed FDG uptake ≤3.15. Asymptomatic malignant lesions were detected with a sensitivity of 100%, a negative predictive value of 100% and a specificity of 45.1%.

CONCLUSION

Malignant transformation of PN also occurs in asymptomatic children and adolescents. Detection of MPNST at early stages could increase the possibility of oncologically curative resections.

Concomitant Malignant Pulmonary Peripheral Nerve Sheath Tumour and Benign Cutaneous Peripheral Nerve Sheath Tumour in a Dog

Peripheral nerve sheath tumours (PNSTs) are neoplastic growths derived from Schwann cells, perineural cells or both. Malignant PNSTs (MPNSTs) are uncommon in domestic animals. This report describes the concomitant occurrence of PNSTs in a 10-year-old female cocker spaniel with a clinical history of respiratory impairment. Grossly, there was a large infiltrative mass in the caudal lobe of the right lung; smaller nodules were observed in the other lobes of the right lung. Furthermore, a small encapsulated cutaneous nodule was observed on the left hindlimb. Histopathology of the pulmonary tumours revealed the proliferation of pleomorphic spindle-shaped cells with moderate mitotic index arranged in interwoven bundles and concentric Antoni A and Antoni B patterns; invasion of the adjacent pulmonary tissue was observed. The cutaneous nodule consisted of neoplastic mesenchymal cells in interwoven bundles with concentric whorls, but without the marked anisokaryosis, binucleation and infiltrative growth seen in the pulmonary tumour. Immunohistochemistry revealed that both tumours were immunoreactive for vimentin, glial fibrillary acidic protein and S100 protein, but were negative for factor VIII. These findings are indicative of a MPNST in the lung with a concomitant benign PNST in the limb. This case represents the first report of a primary MPNST in the lung of a dog. This neoplastic growth should be included in the differential diagnosis of primary malignant pulmonary tumours of dogs.

Immunohistochemistry for trimethylated H3K27 in the diagnosis of malignant peripheral nerve sheath tumours

AIMS

The diagnosis of a malignant peripheral nerve sheath tumour (MPNST) can be challenging, as the morphological criteria and existing immunohistochemical markers are not entirely specific. The recent discovery of frequent inactivation of polycomb repressive complex 2 in MPNSTs suggests that immunohistochemical detection of histone 3 trimethylated on lysine 27 (H3K27me3) could be of diagnostic help. This study aimed to clarify the utility of this marker.

METHODS AND RESULTS

We performed immunostaining studies, with monoclonal (C36B11) and polyclonal antibodies in parallel. With the monoclonal antibody, 56% of 54 conventional MPNSTs showed complete loss of staining, whereas 17% showed mosaic loss and 28% showed intact staining. Three MPNSTs showed a novel geographical pattern of complete loss. All three epithelioid MPNSTs retained intact staining. Among 232 non-MPNSTs, only two (0.9%) showed complete loss of staining. Mosaic loss was observed in 38% of non-MPNSTs, whereas the remaining 61% retained intact staining. For conventional MPNSTs, complete loss of H3K27me3 was significantly associated with a higher TNM stage (P = 0.013), a deeper location (P = 0.004), and the presence of heterologous differentiation (P = 0.003). Polyclonal antibodies did not recognize 34% of cases that showed complete loss with the use of monoclonal antibodies.

CONCLUSIONS

We confirmed that complete loss of H3K27me3 immunohistochemical staining is moderately sensitive and highly specific for MPNSTs. In contrast to prior studies, we found that mosaic loss of H3K27me3 staining is non-specific, and caution that such a pattern should not be considered to be diagnostic. We recommend the use of a monoclonal antibody to obtain better performance.