A document by Minoosh Shabani Barzegar. Click on the document to view its contents.

AbstractBackground: Colorectal cancer is the third most common cancer worldwide, and as such is a significant global health concern. Distant metastases of colorectal cancer to the lung, liver and bone are well documented, while gastrointestinal tract (GIT) metastases are very rare. Herein, we report a case of gastric metastasis from sigmoid colon cancer.Case summary: A 78-year-old male was diagnosed with both gastric and colorectal cancer, which occurred synchronously. The presence of two primary cancers was diagnosed, and radical subtotal gastrectomy and anterior resection were performed simultaneously. The postoperative pathology report showed a moderately differentiated adenocarcinoma in the sigmoid colon and stomach. Immunohistochemical (IHC) analysis revealed that the resected gastric specimens showed tumor cells that were positive for both cytokeratin 20 (CK20) and caudal-type homeobox gene 2 (CDX2), and negative for CK7. This confirmed that the gastric lesion was a metastasis from colorectal cancer.Conclusion: Clinicians should be aware of the potential presence of metastatic gastric cancer, whether synchronous or metachronous, in other solid organ malignancies.Key word: Sigmoid neoplasm; Neoplasm metastasis; Stomach neoplasm; Synchronous; Case reportCore tip: We report a case of gastric metastasis from sigmoid colon cancer. A 78-year-old male was diagnosed gastric cancer and colorectal cancer that occurred synchronously. We performed radical subtotal gastrectomy and anterior resection simultaneously. The postoperative pathology report showed a moderately differentiated adenocarcinoma in the sigmoid colon and stomach. IHC analysis revealed that resected gastric specimens showed tumor cells stained positive for CK20 and CDX2, and negative for CK7. The IHC analysis confirmed that the gastric lesion was metastasis from colorectal cancer. Clinicians should be aware of the potential presence of metastatic gastric cancer in other malignancies of solid organs.INTRODUCTIONColorectal cancer is the third most common cancer worldwide and the second leading cause of cancer-related mortality in the world.[1] Approximately 20% of patients with colorectal cancer already have metastases at the time of initial diagnosis with the liver (50%) and lung (10-15%) being the most commonly involved sites of metastasis from colorectal cancer. Primary cancers from other organs rarely metastasis to the stomach. The rarity of stomach metastasis from colorectal cancer is further supported by a large-scale autopsy study, which reported a range of 0.7-5.4% for gastric metastases across various cancers, indicating that colorectal contributes only minimally within this range.[2] Here, we report a notable case of synchronous metastasis to the stomach in a sigmoid colon cancer patient.CASE PRESENTATIONChief complaints and history of present illness: A 78-year-old male underwent upper and lower endoscopy as part of a routine health examination.History of past illness: The patients had an Alzheimer’s diseaseLaboratory examinations: The carcinoembryonic antigen (CEA) level was 0.87 ng/mlImaging examinations: The esophagogastroduodenoscopy (EGD) revealed a 3x2cm ulcerofungating mass in the lesser curvature side of the mid antrum of the stomach (Figure 1A), and a colonoscopy showed a 4x2cm ulcerofungating mass in the distal sigmoid colon, located 16cm from the anal verge (Figure 1B). The pathological examination of the endoscopic biopsy specimens obtained from the stomach and sigmoid colon indicated well-differentiated adenocarcinoma, which showed similar histologic characteristics with each other. The abdominal computed tomography (CT) scan revealed a tumor involving the antrum to pylorus with peri-gastric infiltration (Figure 2A) and a 5.5 cm sized mass at the distal sigmoid colon (Figure 2B). On positron emission tomography/CT (PET/CT) imaging, only the gastric and colon mass were observed. The diagnosis of double primary cancer was made, and radical subtotal gastrectomy and anterior resection were performed simultaneously.FINAL DIAGNOSISThe postoperative pathology report revealed a moderately differentiated adenocarcinoma in the sigmoid colon (Figure 3A) and stomach (Figure 3B). The Immunohistochemical (IHC) analysis of the gastric lesion showed positive staining for CK20 (Figure 4A) and CDX2 (Figure 4B), and negative staining for CK7 (Figure 4C). These results suggest that the cancer of the sigmoid colon had metastasized to the stomach. The patient recovered uneventfully and was discharged 10 days after surgery without complications. The patient had combined targeted agents with standard cytotoxic chemotherapy.TREATMENTThe initial diagnosis of double primary cancer was made, and radical subtotal gastrectomy and anterior resection were performed simultaneously. The postoperative pathology showed gastric metastasis of sigmoid colon cancer, the patient had combined targeted agents with standard cytotoxic chemotherapy.OUTCOME AND FOLLOW-UPA five-year follow-up was conducted on the patient; this case was then closed due to the absence of evidence of metastasis.DISCUSSIONThe determination of the true incidence of metastasis to the stomach is challenging due to its low prevalence. Several studies have reported an incidence of 0.2-0.8% [3-6] and autopsy studies have reported higher incidences of 1.7-5.4% [4,7-9]. Studies based on autopsy results conducted on individuals with certain neoplasms are a reliable source of actual incidence data.Gastric metastasis from colorectal cancer is rarely documented in the literature [3,4,8,10] and only one case has been reported, found during a routine health check-up with no symptoms. Patients diagnosed with gastric metastasis may present with various symptoms. Green et al. documented that among the ten cases identified through surgical biopsy, notable clinical symptoms and physical examination outcomes encompassed diffuse abdominal pain, nausea and vomiting, anorexia, guaiac-positive stools, and gastrointestinal bleeding.[4]Previous studies have demonstrated that endoscopic patterns, including multiple nodules, bull’s eye pattern, exophytic mass lesions, ulcers, and multiple tumors, are prevalent and characteristic. These findings are often accompanied by doughnut-shaped ridged lesions and volcanic ulcers. These endoscopic patterns have been shown to be useful in the diagnosis of gastric metastases.[11] However, some cases of gastric metastasis are difficult to distinguish from primary gastric cancer.[10,12] Hirano K et al. reported that more than half were solitary metastases. Despite the heterogeneity of the morphologies observed, approximately half of the cases exhibited a resemblance to early gastric cancer.[13] In the present study, EGD revealed an ulcerofungating mass with mucosal invasion, which was diagnosed as typical primary gastric cancer rather than metastatic gastric cancer.In the field of cancer research, a significant body of literature has emerged on the use of immunohistochemical testing for the identification of carcinomas of unknown primary origin. A seminal study by Bayrak R et al. reported the expression of CK7 in upper GIT tumors, whereas CK20 was found to be predominantly expressed in lower GIT tumors.[14] Building on this, Park SY et al. undertook a comprehensive evaluation of multiple immunohistochemical markers for each tumor with the aim of determining the combination of the 10 markers that most effectively predicted primary sites.[15] The most predictive multi-marker phenotypes, as determined by a combination of specificity and positive predictive value, were CDX2+/CK7-/CK20+ for colorectal primary tumors and CDX2+/CK7+/CK20- for upper GI tumors. The patient in question had a CK7-/CK20+ pattern and positive staining for CDX2.In the management of metastatic colorectal cancer, curative surgery is widely accepted as the preferred method for the removal of resectable metastases in the lung or liver. However, for metastases in extremely rare sites, such as the stomach, a consensus on the optimal approach has yet to be established.[16] Nushijima et al. reported a case.[17] A 52-year-old woman was diagnosed with transverse colon cancer, underwent left hemicolectomy and received adjuvant XELOX therapy for 6 months. One year and 3 months after left hemicolectomy, EGD revealed a submucosal tumor in the stomach and histology showed metastatic gastric cancer from transverse colon cancer. Radical distal gastrectomy was performed, but peritoneal dissemination and para-aortic lymph node recurrence were noted 7 months after the second surgery. The prognosis is generally poor because gastric involvement typically indicates an advanced stage of disease and is often associated with metastases to other sites. In our case, metastatic lesion in the stomach were diagnosed simultaneously with the diagnosis of colorectal cancer. Radical resection was performed on both sites with a favorable prognosis. Therefore, it is imperative to perform EGD in patients diagnosed with colorectal cancer.CONCLUSIONTumor metastases to distant anatomical structures can disrupt normal function and significantly increase disease morbidity and mortality. Consequently, metastases from a known primary cancer have a critical impact on staging, prognosis, and treatment strategies. In addition, cancers that initially present with distant metastases often require extensive evaluation to identify the primary site and guide optimal treatment. In conclusion, clinicians should be aware of the potential presence of metastatic gastric cancer, whether synchronous or metachronous, in other solid organ malignancies. Appropriate systemic treatment, including chemotherapy or hormonal therapy for the primary tumor, is the most desirable treatment for metastatic tumors in the stomach; however, surgical resection of metastatic gastric tumors may be recommended to improve the patient’s quality of life if there is a risk of complications such as bleeding or tumor perforation.REFERENCES1 Bray F, Laversanne M, Sung H, Ferlay J, Siegel RL, Soerjomataram I, Jemal A. Global cancer statistics 2022: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries. CA Cancer J Clin 2024; 74 : 229-263 [PMID: 38572751 DOI: 10.3322/caac.21834]2 Disibio G, French SW. Metastatic patterns of cancers: results from a large autopsy study. Arch Pathol Lab Med 2008; 132 : 931-939 [PMID: 18517275 DOI: 10.5858/2008-132-931-MPOCRF]3 Davis GH, Zollinger RW. Metastatic melanoma of the stomach. Am J Surg 1960; 99 : 94-96 [PMID: 13814449 DOI: 10.1016/0002-9610(60)90258-0]4 Green LK. Hematogenous metastases to the stomach. A review of 67 cases.Cancer 1990; 65 : 1596-1600 [PMID: 2311070 DOI: 10.1002/1097-0142(19900401)65:7<1596::aid-cncr2820650724>3.0.co;2-5]5 Higgins PM. Pyloric obstructions due to a metastatic deposit from carcinoma of the bronchus. Can J Surg 1962; 5 : 438-441 [PMID: 13954414]6 Santos-Seoane SM, Perez-Casado L, Helguera-Amezua C, Diez-Fernandez M. Metastatic melanoma of the stomach. Cir Esp (Engl Ed) 2019; 97 : 51 [PMID: 30041824 DOI: 10.1016/j.ciresp.2018.06.012]7 Menuck LS, Amberg JR. Metastatic disease involving the stomach. Am J Dig Dis 1975; 20 : 903-913 [PMID: 1190198 DOI: 10.1007/BF01070875]8 Oda, Kondo H, Yamao T, Saito D, Ono H, Gotoda T, Yamaguchi H, Yoshida S, Shimoda T. Metastatic tumors to the stomach: analysis of 54 patients diagnosed at endoscopy and 347 autopsy cases. Endoscopy 2001; 33 : 507-510 [PMID: 11437044 DOI: 10.1055/s-2001-14960]9 Telerman A, Gerard B, Van den Heule B, Bleiberg H. Gastrointestinal metastases from extra-abdominal tumors. Endoscopy 1985; 17 : 99-101 [PMID: 4006875 DOI: 10.1055/s-2007-1018470]10 Hsu CC, Chen JJ, Changchien CS. Endoscopic features of metastatic tumors in the upper gastrointestinal tract. Endoscopy 1996; 28 : 249-253 [PMID: 8739742 DOI: 10.1055/s-2007-1005437]11 Namikawa T, Hanazaki K. Clinicopathological features and treatment outcomes of metastatic tumors in the stomach. Surg Today 2014; 44 : 1392-1399 [PMID: 23896636 DOI: 10.1007/s00595-013-0671-9]12 Jones GE, Strauss DC, Forshaw MJ, Deere H, Mahedeva U, Mason RC. Breast cancer metastasis to the stomach may mimic primary gastric cancer: report of two cases and review of literature. World J Surg Oncol 2007; 5 : 75 [PMID: 17620117 DOI: 10.1186/1477-7819-5-75]13 Hirano K, Nomura K, Ochiai Y, Hayasaka J, Suzuki Y, Mitsunaga Y, Odagiri H, Masui A, Kikuchi D, Hoteya S. Metastatic Gastric Tumors: Clinical and Endoscopic Features. Cureus 2024; 16 : e58678 [PMID: 38770512 DOI: 10.7759/cureus.58678]14 Bayrak R, Haltas H, Yenidunya S. The value of CDX2 and cytokeratins 7 and 20 expression in differentiating colorectal adenocarcinomas from extraintestinal gastrointestinal adenocarcinomas: cytokeratin 7-/20+ phenotype is more specific than CDX2 antibody.Diagn Pathol 2012; 7 : 9 [PMID: 22268990 DOI: 10.1186/1746-1596-7-9]15 Park SY, Kim BH, Kim JH, Lee S, Kang GH. Panels of immunohistochemical markers help determine primary sites of metastatic adenocarcinoma. Arch Pathol Lab Med 2007;131 : 1561-1567 [PMID: 17922593 DOI: 10.5858/2007-131-1561-POIMHD]16 Terashima S, Watanabe S, Kogure M, Tanaka M. Long-term survival after resection of a gastric metastasis from transverse colon cancer: a case report. Fukushima J Med Sci 2019; 65 : 37-42 [PMID: 31167978 DOI: 10.5387/fms.2018-24]17 Nushijima Y, Nakano K, Sugimoto K, Nakaguchi K, Kan K, Maruyama H, Doi S, Okamura S, Murata K. [A case of metastatic gastric cancer originating from transverse colon cancer]. Gan To Kagaku Ryoho 2014; 41 : 1802-1804 [PMID: 25731335]

Thymic Neuroendocrine Tumor Presenting with Cervical Lymphadenopathy: A Case Report and Diagnostic ChallengeXiaohui Xie2, Jinming Tang, Wenxiang Wang1, Desong Yang1, Kele Qin1*1 Second Department of Thoracic Surgery, Hunan Cancer Hospital, Affiliated Cancer Hospital of Xiangya School of Medicine, Central South University, Tongzipo Road 283, Changsha 410013, China.2Department of Cardiovascular Surgery, the Second Xiangya Hospital, Central South University, Middle Renmin Road 139, Changsha 410011, China.Correspondence: qinkeke@hnca.org.cnAddress: Hunan Cancer Hospital, Tongzipo Road 283, Changsha 410013, China.

Pneumatosis cystoides intestinalis complicated by gastric signet ring cell carcinoma misdiagnosed as gastrointestinal perforation: a case reportYongshuai Lin1, Weimin Wu1, Xin Zhao1, Jun Wang1*1Department of General Surgery, The 928th Hospital of the Joint Logistics Support Force, CPLA, Haikou, 570100, Hainan, China.*Corresponding author. E-mail: wj17547@163.com.

Case ReportRare Presentation of A Viable Secondary Abdominal Ectopic Pregnancy in the Rudimentary Horn of a Bicornuate Uterus: A Case ReportProf. Dr. Shazia Fakhar (Professor of Obstetrics and Gynaecology a)Dr. Irram Asghar (Senior Medical Officer Obstetricsa)Dr. Atif Rana (Consultant Interventional Radiologista)Rida Inam(Medical studentb)

Postural syncope as a rare manifestation of spinal cord injuryYonghong Liu, Boyan Fang, Qiaoxia Zhen (Corresponding Author)Yonghong LiuDepartment of Neurology, Beijing Rehabilitation Hospital Affiliated to Capital Medical University, ChinaID https://orcid.org/0000-0002-1658-7884Corresponding Author: Qiaoxia ZhenDepartment of Neurology, Beijing Rehabilitation Hospital Affiliated to Capital Medical University, ChinaE-mail:869512540@qq.comBoyan FangDepartment of Neurology, Beijing Rehabilitation Hospital Affiliated to Capital Medical University, ChinaE-mail: fangboyanv@163.com

A document by Xiaolong Li. Click on the document to view its contents.

Vertebral Artery Occlusion with Ipsilateral Weakness due to Ischemic Stroke at the Medulla–Cervical Spinal Cord Junction: A Case ReportPeter Felton 1; Yugant Khand 2; Ram Saha 1Department of Neurology, Virginia Commonwealth University, Richmond, Virginia 23298-0599, USA.Nepalese Army Institute of Health Sciences - College of Medicine, Sanobharyang, Kathmandu, 44600 Nepal.AbstractPosterior circulation strokes can present with diverse neurological deficits, some of which challenge conventional localization principles. We report a case of a 74-year-old male with a history of prior right medullary infarct who presented with recurrent symptoms and was found to have a new medullary acute ischemic stroke in the setting of chronic right vertebral artery occlusion. Notably, the patient exhibited ipsilateral limb weakness, a finding attributable to involvement near the pyramidal decussation at the medulla–spinal cord junction. This case underscores the importance of detailed neuroanatomical understanding in vertebrobasilar ischemia and highlights the diagnostic complexity of brainstem strokes.

1. INTRODUCTIONRetinal dysplasia (RD) is defined as the abnormal differentiation of the retina.1-5 True RD may result from failure of the inner and outer layers of the optic cup to be in contact during embryogenesis, resulting in retinal detachment.6-8 In dogs, the most common RD form is characterized by multifocal folds and rosettes in retinas that are otherwise mostly attached to the underlying retinal pigment epithelium.9,10 Larger RD lesions are defined as geographic and may develop in regions of partial retinal detachment.4,11,12 Dysplastic changes typically develop in the canine retina at 45-50 days of gestation and generally can be diagnosed before 10 weeks of age, when the retinal layers are fully developed.1-11Retinal dysplasia can be inherited or acquired. For example, Labrador Retrievers and Samoyeds may be affected by oculoskeletal dysplasia (OSD) or dwarfism associated with RD (drd).13,14 This condition is caused by mutations in either COL9A3 (drd1 in the Labrador Retriever) or COL9A2 (drd2 in the Samoyed).13,14Geographic RD-like lesions that develop later than 10 weeks of age were described in some canine breeds, such as Golden Retrievers, German Shepherds, and Labrador Retrievers.11,13 By routine ophthalmoscopy, these cannot be differentiated from true geographic RD, and they are being diagnosed as such.15,16 However, high-resolution imaging in affected Labrador Retrievers, Golden Retrievers, and German Shepherds revealed that at least some of these geographic RD-like lesions consist of inner retinal plaques with tubular rosettes and vesicle-like structures.11,13,17,18 The pathogenesis of these retinal plaques has not been defined; they may be acquired, but a genetic predisposition has not been ruled out.Geographic RD is recognized as an inherited condition in the Cavalier King Charles Spaniel (CKCS).15,16 The breeding recommendations by the Genetics Committee of the American College of Veterinary Ophthalmologists (ACVO) for RD-affected CKCS are similar to most other canine breeds: While dogs with geographic RD should not be bred, dogs with focal/multifocal RD or retinal folds can still be bred (‘breeder option’).15 The Hereditary Eye Diseases (HED) Committee of the European College of Veterinary Ophthalmologists (ECVO) states that breeding is optional for dogs affected by focal/multifocal or geographic RD unless the breed club issues different advice.16 According to the Blue Book on Ocular Disorders Presumed to Be Inherited in Purebred Dogs, published by the ACVO Genetics Committee, of the 17,092 CKCS examined between 2019 and 2023, 1.6% had geographic RD, while 3.2% had retinal folds.15 Even though these prevalences are higher than in the Labrador Retriever with 0.4% geographic RD and 0.9% retinal folds,15 no detailed morphological and clinical reports on geographic RD in the CKCS have been published to the best of our knowledge. It is unknown if these lesions represent true RD or are similar to the inner retinal plaques that develop later than 10 weeks of age in Labrador Retrievers, Golden Retrievers, and German Shepherds.11,13,17,18 To fill this knowledge gap, our retrospective study aims to describe high-resolution imaging of geographic RD in a CKCS using confocal scanning laser ophthalmoscopy (cSLO), optical coherence tomography (OCT), and OCT angiography (OCTA). We compared our findings with the images of a Labrador Retriever with unilateral inner retinal plaques, since this condition has been previously characterized.11,13,17,18

A document by Chenyang Zhang. Click on the document to view its contents.

A document by Yanmei Li. Click on the document to view its contents.

This report details the urgent management of a life-threatening aortobronchial fistula (ABF) in a 61-year-old male with a history of esophageal cancer surgery, who presented with massive hemoptysis, underscoring the critical role of rapid diagnosis and endovascular intervention in this rare vascular complication. Emergency digital subtraction angiography (DSA) confirmed the ABF, prompting immediate thoracic endovascular aortic repair (TEVAR) with successful deployment of a stent graft, which achieved complete hemostasis, restored aortic integrity, and resulted in an uncomplicated postoperative course without recurrent bleeding. The case reinforces TEVAR as a minimally invasive and definitive therapeutic strategy for ABF, particularly in high-risk surgical candidates, while highlighting the indispensable role of angiographic imaging in acute settings and the need for heightened clinical suspicion in patients with prior thoracic interventions to avert catastrophic outcomes.Keywords: Aortobronchial fistula; Interventional; Thoracic endovascular aortic repair

A document by Kenichiro Yambe. Click on the document to view its contents.

Advanced Ovarian Dysgerminoma with Supraclavicular Lymph Node Metastasis and Peritoneal Carcinomatosis: A Rare Case Report

AuthorsXinjian Pei¹, Jiuhui Han¹*, Jinchao Cao¹, Junzhong Luo¹, Yunshan Su¹Affiliation¹Department of Pediatric Orthopaedics, The Third Hospital of Hebei Medical University, Shijiazhuang, ChinaCorresponding AuthorJiuhui Han Email: 15227178851@163.com

1. IntroductionDimensional changes in bone following tooth extraction are a natural occurrence and can be attributed to both biological and mechanical factors. Following Wolff’s law, the structure and mass of bone are influenced by mechanical stress and strain. Consequently, in the absence of teeth and the associated forces, there is a potential for bone resorption to take place.1 The remodeling of the alveolar bone ridge following tooth extraction results in noteworthy dimensional changes in both the horizontal and vertical planes.2-7 Research indicates that the resorption rate is more pronounced in the horizontal dimension compared to the vertical dimension.4, 7 However, it is essential to recognize that reconstruction and management of complications associated with vertical bone defects present greater challenges post-surgery.8, 9Over the past decades, various techniques have been developed for the vertical reconstruction of each defect, tailored to the specific type and severity of the defect. Notable methods in this field include distraction osteogenesis, block grafting (onlays or inlays, inter-positional grafts), guided bone regeneration (GBR) utilizing non-absorbable membranes, the application of titanium mesh, and the implementation of tent screws.9-18 While there remains a lack of consensus regarding the most suitable method for vertical reconstruction, it is crucial to consider two fundamental factors when implementing any vertical reconstruction technique. Firstly, the presence of supportive bony walls (bone peaks) and the second is the availability of appropriate soft tissue for achieving a tension-free closure.19-21The characteristics of the bone peaks within the edentulous area play a crucial role in determining the regeneration potential of the defect, particularly in relation to the chosen reconstruction technique. In cases with wide vertical defects, where a considerable distance exists between the bone peaks, inadequate angiogenesis often hinders the regenerative potential.19, 20, 22 In circumstances where the potential for bone regeneration is diminished, utilizing autogenous bone, whether as particles or blocks, may be the preferred option to enhance osteogenic properties and promote osteoinductivity.23 In the context of vertical reconstructions, achieving primary closure presents greater challenges than horizontal reconstructions. Utilizing autogenous blocks may offer a reduced risk of early wound exposure compared to non-absorbable membranes or titanium meshes.12, 24, 25 Furthermore, autogenous blocks demonstrate superior space preservation and diminished late resorption relative to autogenous bone particles, highlighting their advantages in vertical reconstruction procedures.26In certain cases, a segment of alveolar bone may be removed along with the tooth root during tooth extraction. When this fragment can be securely repositioned at the defect site, it can serve as an autogenous block, providing a gold-standard option for horizontal and vertical bone reconstruction.This study presents a simple and minimally invasive approach known as the socket wall autogenous bone block approach for vertical reconstruction in conjunction with tooth extraction. This method has the potential to yield significant results in clinical practice.

Successful Interstitial HDR Brachytherapy for Nasal Skin SCC in Xeroderma Pigmentosum: An Eight-Year Follow-Up Case ReportPouya Saraei1, Vita Derakhshandeh2, Ali Bagheri3*1Department of Medical Physics, Faculty of Medicine,Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran2Department of Otorhinolaryngology, Iran University of Medical Sciences, Tehran, Iran.3Interventional Radiotherapy Ward, Department of Radiation Oncology, Golestan Hospital, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran

Septic Arthritis of the Hip in a Premature Neonate Caused by Staphylococcus epidermidis: A Case ReportTaylor E. Arnold, BS; Paige Jones-Brooks, MD; Zackary Shearer, MD; Gwenevere White, MDDepartment of Pediatrics, Division of Neonatology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA