Perineural spread by squamous carcinomas of the head and neck: a morphological study using antiaxonal and antimyelin monoclonal antibodies

Assessment of perineural spread in advanced cutaneous squamous cell carcinomas treated with immunotherapy

BACKGROUND

Cutaneous squamous cell carcinoma (CSCC) has a propensity for perineural spread (PNS) which is associated with poorer treatment outcomes. Immunotherapy is the new standard of care treatment for advanced CSCC resulting in durable responses. PNS is not captured by traditional response assessment criteria used in clinical trials, e.g. RECIST 1.1, and there is limited literature documenting radiological PNS responses to immunotherapy. In this study we assess PNS responses to immunotherapy using a modified grading system.

METHODS

This is an Australian single-center retrospective review of patients with advanced CSCC who were treated with immunotherapy between April 2018 and February 2022 who had evidence of PNS on pre-treatment magnetic-resonance imaging (MRI). The primary outcome was blinded overall radiological response in PNS using graded radiological criteria, post-commencement of immunotherapy. Three defined timepoints (< 5 months, 5-10 months, > 10 months) were reviewed. Secondary outcomes included a correlation between RECIST 1.1 and PNS assessments and the assessment of PNS on fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography (CT).

RESULTS

Twenty CSCC patients treated with immunotherapy were identified. Median age was 75.7 years and 75% (n = 15) were male. All patients had locoregionally advanced disease and no distant metastases. Median follow-up was 18.5 months (range: 2-59). 70% (n = 14) demonstrated a PNS response by 5 months. Three patients experienced pseudoprogression. One patient had PNS progression by the end of study follow up. RECIST 1.1 and PNS responses were largely concordant at > 10 months (Cohen's Kappa 0.62). 5/14 cases had features suspicious for PNS on FDG-PET/CT.

CONCLUSIONS

PNS response to immunotherapy can be documented on MRI using graded radiological criteria. High response rates were seen in PNS with the use of immunotherapy in this cohort and these responses were largely concordant with RECIST 1.1 assessments. FDG-PET/CT demonstrated limited sensitivity in the detection of PNS.

Tumor Abnormality-Oriented Nanomedicine Design

Anticancer nanomedicines have been proven effective in mitigating the side effects of chemotherapeutic drugs. However, challenges remain in augmenting their therapeutic efficacy. Nanomedicines responsive to the pathological abnormalities in the tumor microenvironment (TME) are expected to overcome the biological limitations of conventional nanomedicines, enhance the therapeutic efficacies, and further reduce the side effects. This Review aims to quantitate the various pathological abnormalities in the TME, which may serve as unique endogenous stimuli for the design of stimuli-responsive nanomedicines, and to provide a broad and objective perspective on the current understanding of stimuli-responsive nanomedicines for cancer treatment. We dissect the typical transport process and barriers of cancer drug delivery, highlight the key design principles of stimuli-responsive nanomedicines designed to tackle the series of barriers in the typical drug delivery process, and discuss the "all-into-one" and "one-for-all" strategies for integrating the needed properties for nanomedicines. Ultimately, we provide insight into the challenges and future perspectives toward the clinical translation of stimuli-responsive nanomedicines.

Perineural Spread of Tumor in the Skull Base and Head and Neck

Perineural tumor spread (PNS) is a well-recognized entity in head and neck cancers and represents a mode of metastasis along nerves. The trigeminal and facial nerves are most affected by PNS, and their connections are reviewed. MRI is the most sensitive modality for detecting PNS, and their anatomy and interconnections are reviewed. MRI is the most sensitive modality for detecting PNS, and imaging features of PNS and important imaging checkpoints are reviewed. Optimal imaging protocol and techniques are summarized as well as other entities that can mimic PNS.

Perineural invasion-associated biomarkers for tumor development

Perineural invasion (PNI) is the process of neoplastic invasion of peripheral nerves and is considered to be the fifth mode of cancer metastasis. PNI has been detected in head and neck tumors and pancreatic, prostate, bile duct, gastric, and colorectal cancers. It leads to poor prognostic outcomes and high local recurrence rates. Despite the increasing number of studies on PNI, targeted therapeutic modalities have not been proposed. The identification of PNI-related biomarkers would facilitate the non-invasive and early diagnosis of cancers, the establishment of prognostic panels, and the development of targeted therapeutic approaches. In this review, we compile information on the molecular mediators involved in PNI-associated cancers. The expression and prognostic significance of molecular mediators and their receptors in PNI-associated cancers are analyzed, and the possible mechanisms of action of these mediators in PNI are explored, as well as the association of cells in the microenvironment where PNI occurs.

Adding Concomitant Chemotherapy to Postoperative Radiotherapy in Oral Cavity Carcinoma with Minor Risk Factors: Systematic Review of the Literature and Meta-Analysis

When presenting with major pathological risk factors, adjuvant radio-chemotherapy for oral cavity cancers (OCC) is recommended, but the addition of chemotherapy to radiotherapy (POCRT) when only minor pathological risk factors are present is controversial. A systematic review following the PICO-PRISMA methodology (PROSPERO registration ID: CRD42021267498) was conducted using the PubMed, Embase, and Cochrane libraries. Studies assessing outcomes of POCRT in patients with solely minor risk factors (perineural invasion or lymph vascular invasion; pN1 single; DOI ≥ 5 mm; close margin < 2−5 mm; node-positive level IV or V; pT3 or pT4; multiple lymph nodes without ENE) were evaluated. A meta-analysis technique with a single-arm study was performed. Radiotherapy was combined with chemotherapy in all studies. One study only included patients treated with POCRT. In the other 12 studies, patients were treated with only PORT (12,883 patients) and with POCRT (10,663 patients). Among the patients treated with POCRT, the pooled 3 year OS rate was 72.9% (95%CI: 65.5−79.2%); the pooled 3 year DFS was 70.9% (95%CI: 48.8−86.2%); and the pooled LRFS was 69.8% (95%CI: 46.1−86.1%). Results are in favor of POCRT in terms of OS but not significant for DFS and LRFS, probably due to the heterogeneity of the included studies and a combination of different prognostic factors.

Molecular and Cellular Mechanisms of Perineural Invasion in Oral Squamous Cell Carcinoma: Potential Targets for Therapeutic Intervention

Simple Summary

Squamous cell carcinoma is the most common type of oral cavity cancer. It can spread along and invade nerves in a process called perineural invasion. Perineural invasion can increase the chances of tumor recurrence and reduce survival in patients with oral cancer. Understanding how oral cancer interacts with nerves to facilitate perineural invasion is an important area of research. Targeting key events that contribute to perineural invasion in oral cavity cancer may reduce tumor recurrence and improve survival. In this review, we describe the impact of perineural invasion in oral cancer and the mechanisms that contribute to perineural invasion. Highlighting the key events of perineural invasion is important for the identification and testing of novel therapies for oral cancer with perineural invasion.

Abstract

The most common oral cavity cancer is squamous cell carcinoma (SCC), of which perineural invasion (PNI) is a significant prognostic factor associated with decreased survival and an increased rate of locoregional recurrence. In the classical theory of PNI, cancer was believed to invade nerves directly through the path of least resistance in the perineural space; however, more recent evidence suggests that PNI requires reciprocal signaling interactions between tumor cells and nerve components, particularly Schwann cells. Specifically, head and neck SCC can express neurotrophins and neurotrophin receptors that may contribute to cancer migration towards nerves, PNI, and neuritogenesis towards cancer. Through reciprocal signaling, recent studies also suggest that Schwann cells may play an important role in promoting PNI by migrating toward cancer cells, intercalating, and dispersing cancer, and facilitating cancer migration toward nerves. The interactions of neurotrophins with their high affinity receptors is a new area of interest in the development of pharmaceutical therapies for many types of cancer. In this comprehensive review, we discuss diagnosis and treatment of oral cavity SCC, how PNI affects locoregional recurrence and survival, and the impact of adjuvant therapies on tumors with PNI. We also describe the molecular and cellular mechanisms associated with PNI, including the expression of neurotrophins and their receptors, and highlight potential targets for therapeutic intervention for PNI in oral SCC.

The Adrenergic Nerve Network in Cancer

The central and autonomic nervous systems interact and converge to build up an adrenergic nerve network capable of promoting cancer. While a local adrenergic sympathetic innervation in peripheral solid tumors influences cancer and stromal cell behavior, the brain can participate to the development of cancer through an intermixed dysregulation of the sympathoadrenal system, adrenergic neurons, and the hypothalamo-pituitary-adrenal axis. A deeper understanding of the adrenergic nerve circuitry within the brain and tumors and its interactions with the microenvironment should enable elucidation of original mechanisms of cancer and novel therapeutic strategies.

Are Throat Pain and Otalgia Predictive of Perineural Invasion in Squamous Cell Carcinoma of the Oropharynx?

PURPOSE

Head and neck cancer is often associated with pain and perineural invasion (PNI). The purpose of this study was to determine the association of pain complaints and the microscopic identification of PNI in patients with oropharyngeal squamous cell carcinoma (OPSCC).

PATIENTS AND METHODS

A retrospective cohort study was performed including patients diagnosed with OPSCC from 2010 to 2019. Patients diagnosed and operated on with curative intent at 2 institutions were included. The primary predictor variable was pain (measured as no pain, ear pain, throat pain, or simultaneous pain). Other variables were patient demographics, p16 status, and TNM staging. The primary outcome variable was the histologic presence of PNI. Chi-square analysis was performed to test for any significant associations between pain, T stage, overall stage, and p16 status in relation to PNI outcome. Multivariate logistic regression analysis was used to control for cancer staging variables when testing the association between pain and PNI.

RESULTS

The final sample was composed of 157 subjects of whom 126 were men. The mean age was 59.7 years. Seventy-seven (49.0%) presented with no pain, while 35 (22.3%), 39 (24.8%), and 6 (3.8%) presented with both throat/ear pain, throat pain only, and ear pain only, respectively. Patients with simultaneous pain had 3.41 times higher odds of PNI compared to the no pain group (P = .02), although only pathologic T stage 4 and a diagnosis on the base of the tongue were independent postoperative predictors of PNI (P < .05).

CONCLUSIONS

Our study demonstrates that otalgia is a preoperative predictor of PNI in OPSCC and also demonstrates a trend of increasing pain complaints with PNI.

Review of Perineural Invasion in Keratinocyte Carcinomas

Perineural invasion is an infiltrative process of peripheral nerves by the primary neoplasm within the immediate vicinity. Aggressive forms of keratinocyte carcinomas, such as basal cell and squamous cell carcinomas, may feature perineural invasion, which is often associated with tumor recurrence and poorer prognosis. Diagnosis requires a high clinical suspicion. Imaging and histopathology are used to assess for extent of disease while surgical excision with complete circumferential peripheral and margin assessment is the treatment goal. However, there is still significant uncertainty about adjuvant chemotherapy and definitive management guidelines. Here, we summarize the current understanding of this complex pathogenic process, the clinical presentation, and the significance of perineural inflammation. We also discuss the recommendations about staging, prognosis, adjuvant radiotherapy, and general guidelines for managing keratinocyte carcinomas with perineural invasion. A better understanding of perineural invasion is essential to improve diagnosis, tailor interventions, and mitigate patient morbidity and mortality.

Accuracy of cone-beam computed tomography for the evaluation of mandible invasion by oral squamous cell carcinoma

BACKGROUND

For patients with oral squamous cell carcinoma (OSCC), accurate evaluation of mandible invasion and resection with appropriate boundaries are important for preserving the structure and function of the mandible and preventing local recurrence. Although cone-beam computed tomography (CBCT), which has high spatial resolution, is now widely used in the diagnosis of oral and maxillofacial bone lesions, no studies have systematically evaluated the accuracy of CBCT for evaluating the presence of bone invasion, the boundaries of bone invasion and the presence of nerve invasion. Therefore, this study aimed to systemically explore the accuracy of CBCT in the preoperative assessment of mandibular invasion by OSCC.

METHODS

Thirty mandibular specimens from OSCC patients were collected in this study. The samples were marked and subjected to CBCT examination. Hematoxylin-eosin staining was used for histopathological assessment sed as the gold standard. The evaluation included the presence of bone invasion, the boundaries of bone invasion and the presence of nerve invasion. The CBCT and histopathological boundaries of bone invasion were delineated and merged to compare and calculate the deviation of CBCT in boundary evaluation.

RESULTS

The accuracy of CBCT in evaluating the presence of mandible invasion was 100%, and the accuracy of CBCT in evaluating the presence of nerve invasion was 69.2%. A mean deviation of 2.97 mm was found for assessment of the boundary of bone invasion using CBCT compared with the histopathological standard. The interexaminer agreement and intraexaminer agreement were perfect for the detection of bone invasion and nerve invasion (κ > 0.8). The intraclass correlation coefficient was 0.923 for the consistency test of boundary delineation on CBCT images.

CONCLUSION

CBCT is quite reliable in determining the presence or absence of mandible invasion but not as reliable for nerve invasion. The deviation in bone invasion boundary estimation should be considered in osteotomy for OSCC.

The radiologic (CT/MRI)-pathological correlations of the salivary duct carcinoma (SDC) with hyaline degeneration and peripheral nerve invasion

OBJECTIVES

Salivary duct carcinoma is an aggressive tumour commonly showing local invasion and/or nerve palsy. However, their CT/MRI findings, especially, regarding T2WI, and the diffusion-weighted-image (DWI), were not well known. In this study, we correlated the CT/MRI appearance and the pathological findings containing the nerve invasion cases such as a facial nerve.

METHODS

We reviewed 14 cases of SDC (parotid = 11, submandibular = 2, minor salivary gland = 1) pathologically proven peripheral nerve involvement. Their CT findings of all patient including dynamic contrast-enhancement study､MRI (n = 9) and DWI (n = 6) were also analyzed with histopathological correlation.

RESULTS

On contrast-enhanced CT, the solid component was moderately enhanced. On MRI, T2WI central low signal core (n = 6) with peripheral high intensity rim (n = 5) was frequently observed except heterogeneous low and high (n = 1), diffuse low (n = 1), and high (n = 1) signal cases. The hyaline degenerative area located in the tumour core was poorly enhanced. Eleven tumours had an ill-defined margin, reflecting invasive tumour growth. On DWI, they showed high signal [the central low and peripherally high (n = 4), and diffuse (n = 1), heterogeneously high signal (n = 1)]. The mean ADC value was 1.148 ~ 0.961 x 10-3 mm²/s. With pathological correlation, the central low signal area on T2WI reflected hyaline degeneration. The sites of gross nerve involvement were revealed as tubular or branching structures on CE-CT (n = 3), and MRI (n = 1).

CONCLUSIONS

(1) We frequently observed a central low signal area on T2WI/DWI in SDC. With histopathological correlation, it corresponded to the central hyaline degeneration with the peripheral viable tumour. 2) The gross nerve involvement might be detected as a strongly enhancement structure.

Survival outcomes in locally advanced cutaneous squamous cell carcinoma presenting with clinical perineural invasion alone

BACKGROUND

Cutaneous squamous cell carcinomas (CSCC) involving the head and neck are common, but initial presentation or recurrence limited to the cranial nerves is rare.

METHODS

We conducted a retrospective study of 21 patients with clinical perineural invasion (PNI) from CSCC and no measurable disease by RECIST 1.1. Patients treated with radiotherapy or chemoradiotherapy were included.

RESULTS

The median time from symptom onset until diagnosis was 13.0 months (2.6-83.1). All patients received radiotherapy. Fourteen received concurrent systemic therapy. The median follow-up time was 30.5 months (1.1-106.0). Ten patients recurred, with the majority being locoregional. The 2-year overall survival rate was 85%. The median progression-free survival (PFS) was 21.5 months with an estimated 2-year PFS of 44.5% (95%CI: 22.3-66.8).

CONCLUSIONS

CSCCs with clinical PNI alone are difficult to diagnose and can have a long interval between appearance of symptoms and diagnosis. They can successfully be treated with chemoradiotherapy. However, many patients still suffer from locoregional recurrences.

Are Oral Pain and Otalgia Predictive of Perineural Invasion in Squamous Cell Carcinoma of the Oral Tongue?

PURPOSE

Tongue cancer is often associated with pain and perineural invasion. The purpose of the present study was to determine the association between tongue pain and otalgia and the microscopic identification of perineural invasion (PNI) in patients with squamous cell carcinoma of the tongue (SCCOT).

PATIENTS AND METHODS

A retrospective cohort study was performed of patients with a diagnosis of SCCOT from January 2013 through June 2019. Patients without a history of head and neck cancer, who had SCCOT diagnosed and treated surgically by a single surgeon, were included in the present study. The primary predictor variables were tongue pain and otalgia (presence vs absence of both). Other variables included patient demographic data and TNM stage. The primary outcome variable was the histologic presence of PNI. A χ² analysis was performed to test for any significant associations between pain, T stage, and overall stage in relation to PNI outcome. Multivariate logistic regression analysis was used to control for cancer staging variables when testing the association between pain and PNI.

RESULTS

The sample included 128 subjects, of whom 76 were men. Their mean age was 60 years. Most patients (n = 97; 75.8%) complained of tongue pain and a few (n = 50; 39.1%) complained of otalgia. The patients with otalgia had a 3.15 times greater odds of PNI when controlling for T stage (P = .016) and 3.68 times greater odds of PNI when controlling for overall stage (P = .007). Increasing T stage and overall stage-with the exception of stage II-were also significantly associated with PNI (P ≤ .05).

CONCLUSIONS

Our study has demonstrated a statistically significant association between preoperative otalgia and PNI in a consecutive group of patients presenting with newly diagnosed SCCOT.

Easily detected signs of perineural tumour spread in head and neck cancer

Perineural tumour spread (PNTS) in head and neck oncology is most often caused by squamous cell carcinoma. The most frequently affected nerves are the trigeminal and facial nerves. Up to 40% of patients with PNTS may be asymptomatic. Therefore, the index of suspicion should be high when evaluating imaging studies of patients with head and neck cancer. This review describes a "quick search checklist" of easily detected imaging signs of PNTS. TEACHING POINTS: • A distinctive feature of head and neck tumours is growth along nerves. • Perineural tumour spread is most often caused by squamous cell carcinoma. • There are several key findings for the detection of perineural tumour spread.

Practical clinical guidelines for contouring the trigeminal nerve (V) and its branches in head and neck cancers

PURPOSE

The trigeminal nerve (V) is a major route of tumor spread in several head and neck cancers. However, only limited data are currently available for its precise contouring, although this is absolutely necessary in the era of intensity-modulated radiation therapy (IMRT). The purpose of this article is to present practical clinical guidelines for contouring the trigeminal nerve (V) in head and neck cancers at risk of spread along this nerve.

METHOD

The main types of head and neck cancers associated with risks of spread along the trigeminal nerve (V) and its branches were comprehensively reviewed based on clinical experience, literature-based patterns of failure, anatomy and radio-anatomy. A consensus for contouring was proposed based on a multidisciplinary approach among head and neck oncology experts including radiation oncologists (JBi, ML, MO, VG and JB), a radiologist (VD) and a surgeon (CS). These practical clinical guidelines have been endorsed by the GORTEC (Head and Neck Radiation Oncology Group).

RESULTS

We provided contouring and treatment guidelines, supported by detailed figures and tables to help, for the trigeminal nerve and its branches: the ophthalmic nerve (V1), the maxillary nerve (V2) and the manidibular nerve (V3). A CT- and MRI-based atlas was proposed to illustrate the whole trigeminal nerve pathway with its main branches.

CONCLUSION

Trigeminal nerve (V) invasion is an important component of the natural history of various head and neck cancers. Recognizing the radio-anatomy and potential routes of invasion is essential for optimal contouring, as presented in these guidelines.

L1CAM induces perineural invasion of pancreas cancer cells by upregulation of metalloproteinase expression

Pancreas cancer cells have a tendency to invade along nerves. Such cancerous nerve invasion (CNI) is associated with poor outcome; however, the exact mechanism that drives cancer cells to disseminate along nerves is unknown. Immunohistochemical analysis of human pancreatic ductal adenocarcinoma (PDAC) specimens showed overexpression of the L1 cell adhesion molecule (L1CAM) in cancer cells and in adjacent Schwann cells (SC) in invaded nerves. By modeling the neural microenvironment, we found that L1CAM secreted from SCs acts as a strong chemoattractant to cancer cells, through activation of MAP kinase signaling. L1CAM also upregulated expression of metalloproteinase-2 (MMP-2) and MMP-9 by PDAC cells, through STAT3 activation. Using a transgenic Pdx-1-Cre/KrasG12D /p53R172H (KPC) mouse model, we show that treatment with anti-L1CAM Ab significantly reduces CNI in vivo. We provide evidence of a paracrine response between SCs and cancer cells in the neural niche, which promotes cancer invasion via L1CAM secretion.

Nerve Dependence: From Regeneration to Cancer

Nerve dependence has long been described in animal regeneration, where the outgrowth of axons is necessary to the reconstitution of lost body parts and tissue remodeling in various species. Recent discoveries have demonstrated that denervation can suppress tumor growth and metastasis, pointing to nerve dependence in cancer. Regeneration and cancer share similarities in regard to the stimulatory role of nerves, and there are indications that the stem cell compartment is a preferred target of innervation. Thus, the neurobiology of cancer is an emerging discipline that opens new perspectives in oncology.

The role of perineural invasion in treatment decisions for oral cancer patients: A review of the literature

PURPOSE

The role of perineural invasion (PNI) in the management of patients with oral squamous cell carcinoma (OSSC) is still controversial, and there is no consensus regarding the most appropriate therapeutic approach. The purpose of this study is to review the findings in the literature describing OSCC as a neurotropic malignancy, with the aim of correlating perineural invasion with treatment decisions and disease prognosis.

MATERIALS AND METHODS

A literature search was conducted of references based on the MEDLINE and Cochrane Database of Systematic Reviews, with subject keywords including four main categories: perineural invasion, perineural spread, oral squamous cell cancinoma, neurotropic carcinoma.

RESULTS

In this systematic review and analysis, more than 350 publications met the eligibility criteria of the authors.

CONCLUSION

Perineural invasion (PNI) is a widely recognized indicator of poor prognosis in oral cancer patients, strongly correlating with aggressive tumor behavior, disease recurrence, and increased morbidity and mortality. Elective neck dissection could be an indicator in improving neck control in PNI-positive patients, while the addition of adjuvant postoperative radiotherapy may not significantly improve survival rates. Various molecular markers have been correlated with perineural tumor spread, but further investigations are required before targeting PNI as part of advanced cancer therapies.

Prognostic impact of perineural invasion in hypopharyngeal squamous cell carcinoma

OBJECTIVES

The aim of this study was to evaluate the role of PNI in HPSCC.

METHODS

The medical records of 105 patients who underwent surgery-based treatment for HPSCC were reviewed. Clinicopathologic parameters including disease-specific survival were correlated with PNI.

RESULTS

PNI was identified in 27 of the 105 (25.7%) cases of HPSCC. Correlation analysis demonstrated that PNI in HPSCC was significantly correlated with pN classification (10.3% in N0/N1 vs 34.8% in N2/N3, p = 0.006). Patients with PNI had decreased 5-year disease-specific survival with borderline significance (p = 0.065). In a sub-set of 31 patients who did not receive post-operative radiotherapy, PNI was determined to be a significant prognostic predictor (p = 0.033). In multivariate analysis, extracapsular invasion was the only independent prognostic factor for disease-specific survival (p = 0.001).

CONCLUSION

Perineural invasion (PNI) should be considered an independent predictor for cervical lymph node involvement. PNI status in primary hypopharyngeal squamous cell carcinoma (HPSCC) specimens should be considered in decisions concerning adjuvant radiotherapy.

Correlation of neural cell adhesion molecules with perineural spread of squamous cell carcinoma of the head and neck

Perineural spread (PNS) is a poor prognostic factor associated with increased risk of local recurrence and nodal metastasis and reduced survival of patients with squamous cell carcinoma of the head and neck (SCCHN). There is some evidence to indicate that neural cell adhesion molecules (NCAMs) may play a role in PNS of a variety of tumor types. We performed this study to investigate whether NCAM expression can be used as a predictor of PNS in SCCHN. The surgical specimens of 66 patients with SCCHN were evaluated with monoclonal IgG antibody immunoperoxidase staining for NCAM. Of the 41 specimens with PNS, 38 (93%) showed evidence of NCAM expression. In contrast, only 9 specimens (36%) without PNS expressed NCAMs. The difference in NCAM expression between the study and control groups was statistically significant ( P < 0.01).

Mechanisms of cancer dissemination along nerves

The local extension of cancer cells along nerves is a frequent clinical finding for various tumours. Traditionally, nerve invasion was assumed to occur via the path of least resistance; however, recent animal models and human studies have revealed that cancer cells have an innate ability to actively migrate along axons in a mechanism called neural tracking. The tendency of cancer cells to track along nerves is supported by various cell types in the perineural niche that secrete multiple growth factors and chemokines. We propose that the perineural niche should be considered part of the tumour microenvironment, describe the molecular cues that facilitate neural tracking and suggest methods for its inhibition.

Evaluation of the inferior and superior laryngeal nerve stumps for perineural spread in laryngeal cancer

Objective

Perineural spread (PNS) is an important risk factor for locoregional failure and is correlated with reduced survival rates in squamous cell carcinoma of the larynx. PNS may extend proximally and/or distally in the nerve sheath by leaving unin-volved nerve segments. This method of extension may preclude obtaining tumor-free surgical margins, which may be responsible for recurrent disease. The purpose of this study is to investigate the presence or absence of PNS in extralaryngeal superior and inferior laryngeal nerves in patients who underwent total laryngectomy for squamous cell carcinoma of the larynx.

METHODS

Extralaryngeal segments of superior and inferior laryngeal nerves were resected bilaterally during 15 consecutive laryngectomies. Laryngectomy specimens and the harvested proximal nerve segments were histopathologically examined for the presence or absence of PNS.

RESULTS

Ten of 15 laryngectomy specimens showed PNS; however, none of the extralaryngeal superior or inferior laryngeal nerve segments revealed perineural involvement.

CONCLUSION

Extralaryngeal extension of PNS is highly unlikely in squamous cell carcinoma of the larynx.

In Vitro Modeling of Cancerous Neural Invasion: The Dorsal Root Ganglion Model

One way that solid tumors disseminate is through neural invasion. This route is well-known in cancers of the head and neck, prostate, and pancreas. These neurotropic cancer cells have a unique ability to migrate unidirectionally along nerves towards the central nervous system (CNS). The dorsal root ganglia (DRG)/cancer cell model is a three dimensional (3D) in vitro model frequently used for studying the interaction between neural stroma and cancer cells. In this model, mouse or human cancer cell lines are grown in ECM adjacent to preparations of freshly dissociated cultured DRG. In this article, the DRG isolation protocol from mice, and implantation in petri dishes for co-culturing with pancreatic cancer cells are demonstrated. Five days after implantation, the cancer cells made contact with the DRG neurites. Later, these cells formed bridgeheads to facilitate more extensive polarized, neurotropic migration of cancer cells.

Perineural Spread in Noncutaneous Head and Neck Cancer: New Insights into an Old Problem

Head and neck malignancies have the propensity to invade nerves. Perineural tumor invasion is common, with some series reporting rates of 30 to 100%. Squamous cell carcinoma and adenoid cystic carcinoma are the most commonly involved tumors. The most commonly involved nerves are the trigeminal (cranial nerve [CN] V) and facial (CN VII) and their branches. Neural spread away from a tumor is encountered less often and usually causes specific symptoms such as pain, muscle weakness, and atrophy, depending on the involved nerves. While clinical symptoms and physical examination may suggest the presence of neural invasion, specific imaging modalities such as fat-suppressed T1-weighted magnetic resonance images, should be utilized to identify perineural tumor spread in its early phases. Perineural tumor spread should be considered and addressed in the treatment planning of patients with head and neck or skull base cancers as it can influence the extent of surgery, and the dosage and fields of radiation therapy. In the current review, we discuss the clinical course of perineural tumor spread and its therapeutic implications.

Perineural invasion as a prognostic factor for cervical cancer: a systematic review and meta-analysis

BACKGROUND

Recent observational studies have reported that perineural invasion (PNI) may be a negative prognostic factor in cervical cancer.

OBJECTIVES

The purpose of this meta-analysis is to systematically analyse the effect of PNI on overall survival and disease-free survival.

SEARCH STRATEGY

The PubMed and Cochrane clinical trials databases were searched for articles with publication dates up to September 2013.

SELECTION CRITERIA

Retrospective observational studies with survival analysis for perineural invasion after radical hysterectomy plus lymphadenectomy of cervical cancer were selected.

DATA COLLECTION AND ANALYSIS

Trial characteristics and outcomes and quality measures based on the Newcastle-Ottawa scale (NOS) were independently extracted. The overall survival and disease-free survival of patients with PNI were measured using a hazard ratio (HR) for time to event outcomes.

MAIN RESULTS

The meta-analysis of these studies demonstrated that cervical cancer with PNI was associated with a lower overall survival rate (HR 2.21, 95 % CI 1.36-3.59, P = 0.001). Although the disease-free survival was lower in the PNI group (HR 1.35, 95 % CI 0.78-2.31, P = 0.28), the results were not statistically significant.

CONCLUSION

Patients with PNI-positive cervical cancer have a poor overall survival rate; therefore, we can conclude that perineural invasion (PNI) is an adverse prognostic factor in cervical cancer. Based on these results, PNI should be an independent prognostic factor for cervical cancer and the decision to proceed with adjuvant therapy after surgery.

Prognostic significance of perineural invasion in stage IIA colon cancer

BACKGROUND

Perineural invasion (PNI) may influence the prognosis of colon cancer, but little is known about its predictive value. The aim of this study was to reveal the role of PNI in predicting prognosis after curative resection of colon cancer, especially T3N0.

METHODS

Two hundred and fifty-five patients who underwent curative resection for colon cancer at Samsung Medical Center and were later diagnosed with stage T3N0 by a pathological report between November 2004 and December 2007 were retrospectively recruited into the study.

RESULTS

Among the 255 patients, 156 were male and 99 were female. The mean age was 61 years (range, 25 to 88 years). The most common tumour location was the sigmoid colon (93 patients, 36.5%). The median follow-up period was 61 months (range, 1 to 98 months). PNI was detected in 18 patients (7.1%). Adjuvant chemotherapy was performed in 205 patients (80.4%). The 5-year disease-free survival rate was greater for patients with PNI negative tumours compared with those with PNI positive tumours (92.0% versus 76.0%, P = 0.025). Adjuvant chemotherapy was not associated with significant differences in survival rate (94.8% versus 96.9%, P = 0.625). On multivariate analysis, PNI was an independent prognostic factor for disease-free and overall survival (P = 0.046, hazard ratio (HR) = 3.113, 95% confidence interval (CI) = 1.020-9.505 and P = 0.019, HR = 9.395, 95% CI = 1.453-60.755 respectively).

CONCLUSIONS

PNI is the only significant prognostic factor affecting disease-free and overall survival in patients with T3N0 colon cancer.

The severity of neural invasion is associated with shortened survival in colon cancer

PURPOSE

Neural invasion (NI) is a histopathologic feature of colon cancer that receives little consideration. Therefore, we conducted a morphologic and functional characterization of NI in colon cancer.

EXPERIMENTAL DESIGN

NI was investigated in 673 patients with colon cancer. Localization and severity of NI was determined and related to patient's prognosis and survival. The neuro-affinity of colon cancer cells (HT29, HCT-116, SW620, and DLD-1) was compared with pancreatic cancer (T3M4 and SU86.86) and rectal cancer cells (CMT-93) in the in vitro three-dimensional (3D)-neural-migration assay and analyzed via live-cell imaging. Immunoreactivity of the neuroplasticity marker GAP-43, and the neurotrophic-chemoattractant factors Artemin and nerve growth factor (NGF), was quantified in colon cancer and pancreatic cancer nerves. Dorsal root ganglia of newborn rats were exposed to supernatants of colon cancer, rectal cancer, and pancreatic cancer cells and neurite density was determined.

RESULTS

NI was detected in 210 of 673 patients (31.2%). Although increasing NI severity scores were associated with a significantly poorer survival, presence of NI was not an independent prognostic factor in colon cancer. In the 3D migration assay, colon cancer and rectal cancer cells showed much less neurite-targeted migration when compared with pancreatic cancer cells. Supernatants of pancreatic cancer and rectal cancer cells induced a much higher neurite density than those of colon cancer cells. Accordingly, NGF, Artemin, and GAP-43 were much more pronounced in nerves in pancreatic cancer than in colon cancer.

CONCLUSION

NI is not an independent prognostic factor in colon cancer. The lack of a considerable biologic affinity between colon cancer cells and neurons, the low expression profile of colonic nerves for chemoattractant molecules, and the absence of a major neuroplasticity in colon cancer may explain the low prevalence and impact of NI in colon cancer.

Perineural invasion and spread in head and neck cancer

Perineural involvement is a well-recognized clinicopathologic entity found in head and neck (H&N) cancers, including mucosal epithelial carcinomas and salivary gland malignancies. Perineural disease remains a diagnostic, prognostic and therapeutic challenge for the multidisciplinary H&N oncology team. Nerves are important routes of tumor spread in H&N malignancies, yet the biology and prognostic implications of perineural tumor growth are not fully understood. On balance, the available evidence suggests that it is associated with an increased risk of locoregional recurrence but the impact on survival remains uncertain. Perineural involvement has implications for locoregional disease diagnosis and management. MRI is the best imaging modality to detect tumor extent. Advanced radiotherapy technologies such as intensity-modulated radiation therapy and image-guided radiation therapy have the potential for more accurate targeting and treatment of anatomically complex patterns of disease spread. This review is limited to nondermatologic H&N cancers.

Imaging of perineural spread in head and neck tumours

Perineural tumour spread refers to a contiguous neoplastic extension along a nerve. As it may be clinically silent, imaging plays a pivotal role in the evaluation and delineation of perineural infiltration in head and neck malignancies, which in turn affects treatment planning. This article focuses on the imaging features of perineural spread of head and neck tumours. The important potential perineural pathways and the possible underlying pathogenesis of this phenomenon are also reviewed.

Perineural invasion in cancer: a review of the literature

Perineural invasion (PNI) is the process of neoplastic invasion of nerves and is an under-recognized route of metastatic spread. It is emerging as an important pathologic feature of many malignancies, including those of the pancreas, colon and rectum, prostate, head and neck, biliary tract, and stomach. For many of these malignancies, PNI is a marker of poor outcome and a harbinger of decreased survival. PNI is a distinct pathologic entity that can be observed in the absence of lymphatic or vascular invasion. It can be a source of distant tumor spread well beyond the extent of any local invasion; and, for some tumors, PNI may be the sole route of metastatic spread. Despite increasing recognition of this metastatic process, there has been little progress in the understanding of molecular mechanisms behind PNI and, to date, no targeted treatment modalities aimed at this pathologic entity. The objectives of this review were to lay out a clear definition of PNI to highlight its significance in those malignancies in which it has been studied best. The authors also summarized current theories on the molecular mediators and pathogenesis of PNI and introduced current research models that are leading to advancements in the understanding of this metastatic process.

[Cerebral nerves - perineural tumor spread]

Perineural tumor spread in the course of head and neck tumors is a form of metastatic disease in which the tumor disseminates centrifugally or centripetally along the nerve to (non)contiguous regions. Perineural tumor spread is a potentially devastating complication and has a high impact on the therapeutic management and overall prognosis. In a large proportion of patients the disease remains asymptomatic and imaging (especially MRI) plays a crucial role in the detection of lesions. Familiarity with the pertinent anatomy, knowledge of the common spread pathways and an appropriate imaging strategy allow detection of the perineural spread of the disease in the majority of the cases.

Perineural invasion: identification, significance, and a standardized definition

BACKGROUND

Mohs surgeons have expanded the range of cancers treated using the Mohs technique. Mohs surgeons today are expected to diagnose perineural invasion (PNI) when as little as one nerve is involved.

OBJECTIVE

To address the issue of identification and significance of perineural invasion from the perspective of the Mohs surgeon. The experience of other medical specialties dealing with the same issue are reviewed and applied.

METHODS AND MATERIALS

This article is based on a review of the entire medical literature regarding PNI.

RESULTS

PNI is a significant complication of cancers, regardless of the organ of origin. The most common complication of PNI is recurrence of the cancer. Leptomeningeal carcinomatosis occurs in neglected or aggressive cancers. The process is indolent and contiguous, lending itself well to treatment with Mohs surgery. There are diagnostic mimics of PNI. Variation of reported incidences and cure rates suggest that diagnostic criteria for PNI may not be consistent from study to study.

CONCLUSION

We propose the following definition for the minimum histopathologic criteria required to make a diagnosis of PNI: "In the presence of a malignancy, PNI may be diagnosed according to the observation of cytologically malignant cells in the perineural space of nerves. In equivocal cases, the observation of total or near-total circumferential involvement is supportive, as is the presence of perineural tracking in tangential sections and intraneural involvement."

Perineural tumor spread

Perineural spread (PNS) refers to the extent of tumor cells or other nonneoplastic lesions along the tissues of the nerve sheath, its overall incidence ranges from 2.5% to 5%. PNS is more frequently associated with carcinoma arising from minor or major salivary glands (more often adenoid cystic carcinoma), mucosal or cutaneous squamous cell carcinoma, basal cell carcinoma, melanoma, lymphoma, and sarcoma. Although PNS was previously associated with worsening prognosis, increasing evidence shows that cure is possible. Therefore, radiologists must be aware of the relevant cranial nerve anatomy and thoroughly scrutinize not only the nerves close to the primary tumor site but also the whole neural pathways that can be accessed by PNS. Equally critical is knowledge of the radiologic appearance of perineural tumor extension and the best imaging strategies to detect PNS.

Patterns of mandibular invasion in oral squamous cell carcinoma of the mandibular region

BACKGROUND

Mandibular resections are routinely carried out for achieving a R0 resection for oral cancers. However, the need of mandibular resection to achieve this has always been questioned. The present study was carried out to define the pattern of mandibular involvement in carcinoma of the mandibular region.

PATIENTS AND METHODS

A total of 25 consecutive patients who had undergone mandibular resection and were found to have mandibular invasion were studied in a prospective open fashion. After decalcification the specimens were serially sectioned at 1 cm interval to identify invasion of mandibular bone. Type of invasion, route of spread and host cell reactions were also recorded.

RESULTS

The mandibular involvement was infiltrative in 14(56%) and erosive in 11(44%). It was cortical in 5(20%), marrow involvement was seen in 15(60%) while 5(20%) had spread through the inferior alveolar canal. Of the 25, 24(96%) lesions were located with in 1 cm of the mandible.

CONCLUSION

The possibility of mandibular involvement is higher in patients where tumours are located with in 1 cm of the mandible. Involvement of mandible through the canal of inferior alveolar nerve in the present study was relatively high (20%). Therefore it is recommended that before a decision is taken to preserve the mandible it should be thoroughly screened for possible involvement.

Perineural spread in head and neck malignancies

Perineural tumor spread (PNS) of head and neck malignancies is a well-known form of metastatic disease in which a lesion can migrate away from the primary site along the endoneurium or perineurium. This pattern of spread may create a poor prognosis and require aggressive treatment when curable. Although representative histologies are squamous cell carcinoma and adenoid cystic carcinoma, other malignancies such as malignant lymphoma and sarcoma also can show such a specific pattern of extent. PNS can be insidious, often delaying diagnosis. Knowledge of anatomy of the nerves is crucial in the imaging diagnosis of PNS, to detect early curable disease. The facial nerve and the maxillary and mandibular divisions of the trigeminal nerve are most commonly affected. General clinical issues and the diagnostic imaging of PNS along these nerves are discussed in the current article.

Perineural spread of cutaneous malignancy to the brain

BACKGROUND

The retrospective analysis was performed to investigate the role of stereotactic radiotherapy (SRT) techniques for patients with intracranial perineural spread (PNS) of a primary cutaneous malignancy.

METHODS

Five patients were identified who received SRT from 1993 to 2003 for cutaneous malignancies with intracranial PNS to the cavernous sinus (n = 3) or Meckel's cave (n = 2). Patients were treated with GammaKnife stereotactic radiosurgery (n = 2), linear accelerator (linac)-based fractionated SRT (n = 2), or linac-based stereotactic radiosurgery (n = 1).

RESULTS

The median overall survival (OS) periods from diagnoses of cutaneous malignancy and intracranial PNS were 63.0 months (range, 22.0-102.2 months) and 25.5 months (range, 22.0-55.2 months), respectively. The median OS from SRT was 24.2 months (range, 19.5-53.2 months). One patient was alive and without evidence of disease at 53 months of follow-up. The median durations of local and regional control from SRT were 19.5 months (range, 1.5-53.2 months) and 7.0 months (range, 1.5-53.2 months), respectively.

CONCLUSIONS

Previous reports generally have recommended that patients with intracranial PNS receive palliative external-beam radiotherapy. Results from the current study suggest that some of these patients may have prolonged survival, or even may be cured. Judicious use of SRT should be considered in their management.