Pancreatic Cancer: Current Options for Diagnosis, Staging and Therapeutic Management

MicroRNAs as the critical regulators of epithelial mesenchymal transition in pancreatic tumor cells

Pancreatic cancer (PC), as one of the main endocrine and digestive systems malignancies has the highest cancer related mortality in the world. Lack of the evident clinical symptoms and appropriate diagnostic markers in the early stages of tumor progression are the main reasons of the high mortality rate among PC patients. Therefore, it is necessary to investigate the molecular pathways involved in the PC progression, in order to introduce novel early diagnostic methods. Epithelial mesenchymal transition (EMT) is a critical cellular process associated with pancreatic tumor cells invasion and distant metastasis. MicroRNAs (miRNAs) are also important regulators of EMT process. In the present review, we discussed the role of miRNAs in regulation of EMT process during PC progression. It has been reported that the miRNAs mainly regulate the EMT process in pancreatic tumor cells through the regulation of EMT-specific transcription factors and several signaling pathways such as WNT, NOTCH, TGF-β, JAK/STAT, and PI3K/AKT. Considering the high stability of miRNAs in body fluids and their role in regulation of EMT process, they can be introduced as the non-invasive diagnostic markers in the early stages of malignant pancreatic tumors. This review paves the way to introduce a non-invasive EMT based panel marker for the early tumor detection among PC patients.

Pancreatic cancer with synchronous peritoneal and hepatic metastases: A case report

Introduction and importance: There is evidence that patients with limited peritoneal carcinomatosis of pancreatic cancer or those with low burden of hepatic metastases are amenable to surgical resection. A case report of a patient with cancer of the pancreatic tail and synchronous peritoneal and hepatic metastases is presented.

CASE PRESENTATION

A male patient, 66 years old, underwent cytoreductive surgery (CRS) plus hyperthermic intraperitoneal chemotherapy (HIPEC) and radio-frequency ablation (RFA) for synchronous hepatic metastases simultaneously to distal pancreatectomy for adenocarcinoma of the pancreas. Adjuvant chemotherapy followed the R0 surgery. The patient remained disease free for 18 months, developed liver recurrence and died 28 months after the initial operation.

DISCUSSION

CRS plus HIPEC with synchronous ablation or resection of hepatic metastases may be used for the treatment of pancreatic cancer with synchronous peritoneal and hepatic metastases in highly selected patients.

CONCLUSION

Further studies are needed to confirm whether patients with synchronous peritoneal and hepatic metastases are offered survival benefit from complex surgical intervention (CRS plus HIPEC combined with hepatic resection or RFA).

Intra-arterial Chemotherapy in Patients With Metastatic or Locally Aggressive Pancreatic Adenocarcinoma: A Scoping Review

Pancreatic adenocarcinoma refers to cancer of the pancreatic duct cells. It is normally diagnosed when it is at an advanced stage, making the prognosis poor. Systemic chemotherapy is the primary treatment approach for locally advanced or metastatic pancreatic cancer and has been shown to improve survival by eight to 16 weeks. However, it does not directly penetrate malignant tissue and has many side effects, such as hair loss, bone marrow suppression, and many gastrointestinal issues. A newer treatment modality, regional intra-arterial chemotherapy (IAC), focuses on targeting malignant tissue directly to improve survival and decrease systemic side effects. When IAC is used with gemcitabine (GEM) or FLEC (5-fluorouracil, leucovorin, epirubicin, and carboplatin), the response rate for advanced pancreatic cancer is significantly improved. This literature review introduces the use of hepatic intra-arterial chemotherapy in patients with metastatic pancreatic adenocarcinoma.

Registry-derived stage (RD-Stage) for capturing stage at diagnosis for pancreatic carcinoma in Australia

INTRODUCTION

Stage of pancreatic carcinoma at diagnosis is a strong prognostic indicator of morbidity and mortality, yet is poorly notified to population-based cancer registries ("cancer registries"). Registry-derived stage (RD-Stage) provides a method for cancer registries to use available data sources to compile and record stage in a consistent way. This project describes the development and validation of rules to capture RD-Stage (pancreatic carcinoma) and applies the rules to data currently captured in each Australian cancer registry.

MATERIALS AND METHODS

Rules for deriving RD-stage (pancreatic carcinoma) were developed using the American Joint Commission on Cancer (AJCC) Staging Manual 8th edition and endorsed by an Expert Working Group comprising specialists responsible for delivering care to patients diagnosed with pancreatic carcinoma, cancer registry epidemiologists and medical coders. Completeness of data fields required to calculate RD-Stage (pancreatic carcinoma) and an overall proportion of cases for whom RD stage could be assigned was assessed using data collected by each Australian cancer registry, for period 2018-2019. A validation study compared RD-Stage (pancreatic carcinoma) calculated by the Victorian Cancer Registry with clinical stage captured by the Upper Gastro-intestinal Cancer Registry (UGICR).

RESULTS

RD-Stage (pancreatic carcinoma) could not be calculated in 4/8 (50%) of cancer registries; one did not collect the required data elements while three used a staging system not compatible with RD-Stage requirements. Of the four cancer registries able to calculate RD-Stage, baseline completeness ranged from 9% to 76%. Validation of RD-Stage (pancreatic carcinoma) with UGICR data indicated that there was insufficient data available in VCR to stage 174/457 (38%) cases and that stage was unknown in 189/457 (41%) cases in the UGICR. Yet, where it could be derived, there was very good concordance at stage level (I, II, III, IV) between the two datasets. (95.2% concordance], Kendall's coefficient = 0.92).

CONCLUSION

There is a lack of standardisation of data elements and data sources available to cancer registries at a national level, resulting in poor capacity to currently capture RD-Stage (pancreatic carcinoma). RD-Stage provides an excellent tool to cancer registries to capture stage when data elements required to calculate it are available to cancer registries.

Predictive role of radiomics features extracted from preoperative cross-sectional imaging of pancreatic ductal adenocarcinoma in detecting lymph node metastasis: a systemic review and meta-analysis

Lymph node metastases are associated with poor clinical outcomes in pancreatic ductal adenocarcinoma (PDAC). In preoperative imaging, conventional diagnostic modalities do not provide the desired accuracy in diagnosing lymph node metastasis. The current review aims to determine the pooled diagnostic profile of studies examining the role of radiomics features in detecting lymph node metastasis in PDAC. PubMed, Google Scholar, and Embase databases were searched for relevant articles. The quality of the studies was examined using the Radiomics Quality Score and Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) tools. Pooled results for sensitivity, specificity, likelihood, and odds ratios with the corresponding 95% confidence intervals (CIs) were calculated using a random-effect model (DerSimonian-Liard method). No significant publication bias was detected among the studies included in this meta-analysis. The pooled sensitivity of the validation datasets included in the study was 77.4% (72.7%, 81.5%) and pooled specificity was 72.4% (63.8, 79.6%). The diagnostic odds ratio of the validation datasets was 9.6 (6.0, 15.2). No statistically significant heterogeneity was detected for sensitivity and odds ratio (P values of 0.3 and 0.08, respectively). However, there was significant heterogeneity concerning specificity (P = 0.003). The pretest probability of having lymph node metastasis in the pooled databases was 52% and a positive post-test probability was 76% after the radiomics features were used, showing a net benefit of 24%. Classifiers trained on radiomics features extracted from preoperative images can improve the sensitivity and specificity of conventional cross-sectional imaging in detecting lymph node metastasis in PDAC.

Prognostic Implications of Intratumoral and Peritumoral Infiltrating Lymphocytes in Pancreatic Ductal Adenocarcinoma

This study aimed to elucidate the prognostic implications of intratumoral and peritumoral infiltrating T-lymphocytes in pancreatic ductal adenocarcinoma (PDAC) through a meta-analysis. A total of 18 eligible studies and 2453 PDAC patients were included in the present study. Intratumoral and peritumoral infiltrating lymphocytes were evaluated using various markers, such as CD3, CD4, CD8, FOXP3, and immune cell score. The correlations between these parameters and overall and disease-free survival were investigated and used in the meta-analysis. High intratumoral infiltration of CD3-, CD4-, and CD8-expressing lymphocytes was significantly correlated with better overall survival (hazard ratio (HR) 0.747, 95% confidence interval (CI) 0.620-0.900, HR 0.755, 95% CI 0.632-0.902, and HR 0.754, 95% CI 0.611-0.930, respectively). However, there was no significant correlation between PDAC prognosis and intratumoral FOXP3 or immune cell score (HR 1.358, 95% CI 1.115-1.655 and HR 0.776, 95% CI 0.566-1.065, respectively). Moreover, there was no significant correlation between the prognosis and peritumoral infiltrating T-lymphocytes. In evaluations of disease-free survival, only high intratumoral CD4 infiltration was correlated with a better prognosis (HR 0.525, 95% CI 0.341-0.810). Our results showed that high intratumoral infiltrating lymphocytes were significantly correlated with a better PDAC prognosis. However, among the tumor-infiltrating lymphocytes, CD3, CD4, and CD8 had prognostic implications, but not FOXP3 and immune cell score.

Pancreatic Cancer Microenvironment and Cellular Composition: Current Understandings and Therapeutic Approaches

Pancreatic ductal adenocarcinoma (PDAC) remains one of the most lethal human solid tumors, despite great efforts in improving therapeutics over the past few decades. In PDAC, the distinct characteristic of the tumor microenvironment (TME) is the main barrier for developing effective treatments. PDAC TME is characterized by a dense stroma, cancer-associated fibroblasts, and immune cells populations that crosstalk to the subpopulations of neoplastic cells that include cancer stem cells (CSCs). The heterogeneity in TME is also exhibited in the diversity and dynamics of acellular components, including the Extracellular matrix (ECM), cytokines, growth factors, and secreted ligands to signaling pathways. These contribute to drug resistance, metastasis, and relapse in PDAC. However, clinical trials targeting TME components have often reported unexpected results and still have not benefited patients. The failures in those trials and various efforts to understand the PDAC biology demonstrate the highly heterogeneous and multi-faceted TME compositions and the complexity of their interplay within TME. Hence, further functional and mechanistic insight is needed. In this review, we will present a current understanding of PDAC biology with a focus on the heterogeneity in TME and crosstalk among its components. We also discuss clinical challenges and the arising therapeutic opportunities in PDAC research.

Predicting postoperative pancreatic fistula in pancreatic head resections: which score fits all?

Purpose

Postoperative pancreatic fistula (POPF) is a major complication of pancreatic surgery and can be fatal. Better stratification of patients into risk groups may help to select those who might benefit from strategies to prevent complications. The aim of this study was to validate ten prognostic scores in patients who underwent pancreatic head surgery.

Methods

A total of 364 patients were included in this study between September 2012 and August 2017. Ten risk scores were applied to this cohort. Univariate and multivariate analyses were performed considering all risk factors in the scores. Furthermore, the stratification of patients into risk categories was statistically tested.

Results

Nine of the scores (Ansorge et al., Braga et al., Callery et al., Graham et al., Kantor et al., Mungroop et al., Roberts et al., Yamamoto et al. and Wellner et al.) showed strong prognostic stratification for developing POPF (p < 0.001). There was no significant prognostic value for the Fujiwara et al. risk score. Histology, pancreatic duct diameter, intraabdominal fat thickness in computed tomography findings, body mass index, and C-reactive protein were independent prognostic factors on multivariate analysis.

Conclusion

Most risk scores tend to stratify patients correctly according to risk for POPF. Nevertheless, except for the fistula risk score (Callery et al.) and its alternative version (Mungroop et al.), many of the published risk scores are obscure even for the dedicated pancreatic surgeon in terms of their clinical practicability. There is a need for future studies to provide strategies for preventing POPF and managing patients with high-risk stigmata.

TGFB1/INHBA Homodimer/Nodal-SMAD2/3 Signaling Network: A Pivotal Molecular Target in PDAC Treatment

Pancreatic cancer remains a grueling disease that is projected to become the second-deadliest cancer in the next decade. Standard treatment of pancreatic cancer is chemotherapy, which mainly targets the differentiated population of tumor cells; however, it paradoxically sets the roots of tumor relapse by the selective enrichment of intrinsically chemoresistant pancreatic cancer stem cells that are equipped with an indefinite capacity for self-renewal and differentiation, resulting in tumor regeneration and an overall anemic response to chemotherapy. Crosstalk between pancreatic tumor cells and the surrounding stromal microenvironment is also involved in the development of chemoresistance by creating a supportive niche, which enhances the stemness features and tumorigenicity of pancreatic cancer cells. In addition, the desmoplastic nature of the tumor-associated stroma acts as a physical barrier, which limits the intratumoral delivery of chemotherapeutics. In this review, we mainly focus on the transforming growth factor beta 1 (TGFB1)/inhibin subunit beta A (INHBA) homodimer/Nodal-SMAD2/3 signaling network in pancreatic cancer as a pivotal central node that regulates multiple key mechanisms involved in the development of chemoresistance, including enhancement of the stem cell-like properties and tumorigenicity of pancreatic cancer cells, mediating cooperative interactions between pancreatic cancer cells and the surrounding stroma, as well as regulating the deposition of extracellular matrix proteins within the tumor microenvironment.

The potential of endoscopic ultrasound sonography (EUS)-elastography in determining the stage of pancreatic tumor

AIM

The current study was designed to evaluate the role of semi-quantitative EUS- elastography (strain ratio) in staging malignant pancreatic lesions.

BACKGROUND

Pancreatic cancer is considered one of the most lethal malignancies with a survival rate of only 5% worldwide. Pancreatic lesions include a wide range of diagnoses from benign to malignant forms. Biopsy and pathological study are the gold standard for the differentiation of malignant lesions and staging of tumors. Recently, endoscopic ultrasound sonography (EUS) elastography has been noticed as a non-invasive diagnosis modality. Nevertheless, no evidence of its potential to determine different stages of malignant tumors is available.

METHODS

This prospective study included 81 adult patients with a confirmed diagnosis of malignant pancreatic lesion in different clarified stages. All diagnoses were confirmed after endoscopic ultrasound sonography via pathological investigation of surgical specimens or needle biopsies. The results of EUS-elastography based on tumor size (T staging), involved lymph nodes (N staging), and metastasis (M staging) were compared with the gold standard.

RESULTS

The mean age of patients was 60.11±13.57 years. The mean SR elastography value was 52.78±48.97. Elastography could not significantly discriminate T stage, N stage, or M stage of tumors (p=0.57, p=0.92, p=0.11, respectively). Moreover, the Spearman rank correlation coefficients for the correlation between T staging, N staging, M staging and SR elastography were not significant (p=0.40, p=0.94, p=0.39, respectively).

CONCLUSION

The non-invasive modality EUS-elastography cannot replace the gold standard in staging tumors; however, EUS-elastography seemed to differentiate benign lesions from malignant ones.

The cytologic and immunohistochemical findings of pancreatic mixed acinar-endocrine carcinoma

BACKGROUND

The classification of epithelioid pancreatic neoplasms based on fine-needle aspiration (FNA) is important for proper management, as distinction of pancreatic neuroendocrine neoplasms from other similar appearing lesions can result in significantly different treatment. Mixed acinar-endocrine carcinomas (MAEC) are genetically related to acinar carcinomas and are treated as such. We reviewed cases of MAEC to better characterize their cytologic and immunohistochemical features.

METHODS

Eight FNAs of MAECs were identified and reviewed. A chart review for each case was conducted.

RESULTS

All patients were male, 42-68 years of age, and presented with either Stage 3 or 4 disease. Smear backgrounds of all cases showed naked nuclei without significant necrosis. The smears were cellular with cells arranged in either three-dimensional (3D) clusters with intervening capillaries or singly dispersed. Acinar formation was a prominent feature. Cells were round to oval with small to moderate amounts of delicate cytoplasm. The nuclei were round to oval with mild to moderate anisonucleosis with granular chromatin and small nucleoli. Apoptotic bodies and mitoses were noted in most cases, with Ki67 indices of 10%-48%. All tumors, by definition, demonstrated expression of trypsin and synaptophysin with variable chromogranin expression (50%).

CONCLUSION

The cytology of acinar cell carcinoma shares features with aspirates of other nonductal adenocarcinoma neoplasms of the pancreas. A clue to the diagnosis is that tumors show high Ki67 indices and a diagnosis of MAEC should be excluded anytime a diagnosis of Grade 2 or 3 well-differentiated neuroendocrine tumor or high-grade neuroendocrine carcinoma is in the differential.

Significance of Expression of Cancer Stem Cell Markers CD133 and Nestin in Pancreatic Intraepithelial Carcinoma-invasive Adenocarcinoma Sequence

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive malignancies and one of the most leading causes of cancer related deaths. It has a very poor prognosis with high recurrence rate. We investigated the expression of CSC markers (CD133 and nestin) in 100 patients [30 pancreatic intraepithelial tumor cases (PanIN) and 70 PDAC cases] and correlate the expression levels of these markers with clinicopathological data with the aid of Ki67 expression. Our findings showed that both cancer stem markers are related to the grade, stage, metastasis of PDAC and to the grade of PanIN cases and revealed that both markers are associated with PanIN-PDAC sequence with inverse relation between them. Both markers may contribute to proliferation, differentiation, invasiveness, and histologic types of PDAC. Sothey may also be useful for developing new therapeutic modalities for PDAC.

Preoperative EUS-guided FNA: effects on peritoneal recurrence and survival in patients with pancreatic cancer

BACKGROUND AND AIMS

EUS-guided FNA (EUS-FNA) is an accurate and relatively safe tissue confirmation method for pancreatic cancer. However, there is concern that this procedure may spread tumor cells along the needle track or within the peritoneum. We aimed to estimate the effect of preoperative EUS-FNA on the risk of peritoneal recurrence and long-term outcomes in resected pancreatic cancer.

METHODS

We retrospectively reviewed records of patients diagnosed with pancreatic cancer who had undergone curative resection between 2009 and 2013 to investigate the overall survival, cancer-free survival, and peritoneal recurrence. Peritoneal recurrence was diagnosed based on image findings or cytology-confirmed ascites.

RESULTS

Of 411 patients, 90 underwent preoperative EUS-FNA (EUS-FNA group), whereas 321 did not (non-EUS-FNA group). The median length of follow-up was 16.2 months (range, 2-46). Peritoneal recurrence occurred in 131 patients: 30% (27/90) in the EUS-FNA group versus 32% (104/321) in the non-EUS-FNA group (P = .66). Cancer-free survival or overall survival was not significantly different between the 2 groups: median overall survival of 25.3 months in the EUS-FNA group versus 23.7 months in the non-EUS-FNA group (P = .36) and median cancer-free survival of 12.7 months in the EUS-FNA group versus 11.6 months in the non-EUS-FNA group (P = .38).

CONCLUSIONS

Preoperative EUS-FNA for pancreatic cancer was not associated with an increased rate of peritoneal recurrence or mortality. Therefore, EUS-FNA is an accurate and safe method to obtain suspicious pancreatic mass tissue.

EZH2-Mediated microRNA-139-5p Regulates Epithelial-Mesenchymal Transition and Lymph Node Metastasis of Pancreatic Cancer

Pancreatic cancer (PC) is one of the most aggressive cancers presenting with high rates of invasion and metastasis, and unfavorable prognoses. The current study aims to investigate whether EZH2/miR-139-5p axis affects epithelial-mesenchymal transition (EMT) and lymph node metastasis (LNM) in PC, and the mechanism how EZH2 regulates miR-139-5p. Human PC and adjacent normal tissues were collected to determine expression of EZH2 and miR-139-5p, and their relationship with clinicopathological features of PC. Human PC cell line was selected, and treated with miR-139-5p mimics/inhibitors, EZH2 vector or shEZH2 in order to validate the regulation of EZH2-mediated miR-139-5p in PC cells. Dual-luciferase report gene assay and chromatin immunoprecipitation assay were employed to identify the relationship between miR-139-5p and EZH2. RT-qPCR and Western blot analysis were conducted to determine the expression of miR-139-5p, EZH2 and EMT-related markers and ZEB1/2. Tumor formation ability and in vitro cell activity were also analyzed. Highly-expressed EZH2 and poorly-expressed miR-139-5p were detected in PC tissues, and miR-139-5p and EZH2 expressions were associated with patients at Stage III/IV, with LNM and highly-differentiated tumors. EZH2 suppressed the expression of miR-139-5p through up-regulating Histone 3 Lysine 27 Trimethylation (H3K27me3). EMT, cell proliferation, migration and invasion were impeded, and tumor formation and LNM were reduced in PC cells transfected with miR-139-5p mimics and shEZH2. MiR-139-5p transcription is inhibited by EZH2 through up-regulating H3K27me3, thereby down-regulation of EZH2 and up-regulation of miR-139-5p impede EMT and LNM in PC. In addition, the EZH2/miR-139-5p axis presents as a promising therapeutic strategy for the treatment of PC.

Elevated systemic levels of the matrix metalloproteinase inhibitor TIMP-1 correlate with clinical markers of cachexia in patients with chronic pancreatitis and pancreatic cancer

BACKGROUND

Tissue inhibitor of metalloproteinases-1 (TIMP-1) is a candidate diagnostic and prognostic biomarker for pancreatic ductal adenocarcinoma (PDAC). Here, we determined the possible association of systemic TIMP-1 levels with cachexia and jaundice, two common PDAC-associated conditions.

METHODS

Plasma TIMP-1 was measured by ELISA in patients diagnosed with PDAC (n = 36) and chronic pancreatitis (CP) (n = 25). Patients without pancreatic pathologies and known malignancies of other origin served as controls (n = 13). TIMP-1 levels in these patients were tested for asscociation with jaundice and chachexia, and furthermore correlated with cachexia-related clinical parameters such as weight loss and ferritin, parameters of lung function, hemoglobin and liver synthesis parameters.

RESULTS

TIMP-1 plasma levels were mostly higher in CP and PDAC patients with concomitant jaundice or cachexia. Elevated plasma TIMP-1 levels were also associated with clinical cachexia markers, including absolute and relative values of weight loss and lung function, as well as ferritin, hemoglobin, and cholinesterase levels. TIMP-1 levels significantly correlated with cachexia only in patients without jaundice. Jaundice also impaired the use of TIMP-1 as a prognostic marker in cancer patients. Relating to cachexia status alone, a slightly improved association of TIMP-1 levels with survival of PDAC patients was observed.

CONCLUSION

This retrospective study reports for the first time that plasma levels of TIMP-1 are associated with pancreatic lesion-induced cachexia in patients without jaundice. TIMP-1 is counterindicated as a survival marker in patients with jaundice.

miR-135b-5p Promotes migration, invasion and EMT of pancreatic cancer cells by targeting NR3C2

The exact mechanisms of metastasis for pancreatic cancer remain to be uncovered. This study aimed to elucidate the potential functional mechanism of miR-135b-5p in migration, invasion and epithelial-to-mesenchymal transition (EMT) of pancreatic cancer cells. By real-time PCR and analysis of GEO database, we determined the up-regulated expression of miR-135b-5p in pancreatic cancer tissues and cell lines. Clinically, highly expressed miR-135b-5p was closely related to advanced TNM stage, more lymph node metastasis, more distant metastasis and worse overall survival (OS) and disease-free survival (DFS). Functionally, Transwell assays indicated that miR-135b-5p was a promoter for migration and invasion of pancreatic cancer cells. Additionally, immunohistochemistry staining and Western blot showed that highly expressed miR-135b-5p accelerated EMT process of pancreatic cancer cells. Furthermore, a series of experiments and rescue experiments revealed that Nuclear Receptor Subfamily 3 Group C Member 2 (NR3C2) was the target of miR-135b-5p in pancreatic cancer cells, mediating the promotion effects of miR-135b-5p on the tumor cells migration, invasion and EMT. In conclusion, miR-135b-5p, maybe a novel therapeutic target for pancreatic cancer, promoted migration, invasion and EMT of pancreatic cancer cells by targeting NR3C2.

Squamous cell carcinoma of the pancreas: A systematic review and pooled survival analysis

The diagnosis and treatment of squamous cell carcinoma of the pancreas pose dilemmas in the clinical practice. The present study was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Eligible articles were sought in MEDLINE up to 30th April 2016. A pooled Cox regression analysis was performed to evaluate factors potentially associated with overall survival (OS) and relapse-free survival (RFS). Fifty-four cases of pure squamous cell pancreatic carcinomas were identified in total. The mean age was 61.9 years, and most patients were males (61.1%). The median OS was 7 months. Resectability (p = 0.003) and more recent publication year (p < 0.001) were associated with better OS, as was low/intermediate tumour grade (p = 0.032) with RFS. Despite its poor prognosis, survival rates of pancreatic squamous cell carcinoma seem improved during the recent years; resectability and low/intermediate grade emerged as favourable prognostic factors. Collaborative epidemiological studies are deemed necessary to further validate the results stemming from the published case reports of this rare entity.