Two Cases of Adrenal Cysts Lined by Thyroid Follicular Epithelium: Addressing Cellular Origin and Malignancy Concerns.

Adrenal cysts lined by thyroid follicular epithelium are rare, with only 14 reported cases of "ectopic thyroid tissue" to date. While the primary consideration for differential diagnosis is thyroid carcinoma metastasis, exclusion of metastases is determined based on the absence of a primary thyroid lesion, serological euthyroidism, lack of thyroglobulin elevation, and absence of epithelial atypia. Herein, we report 2 cases of adrenal cysts lined by thyroid follicular epithelium. Case 1 was a 60-year-old woman with a right adrenal cyst. Case 2 was a 51-year-old man with a left adrenal cyst. Over time, both cysts became larger, necessitating an adrenalectomy. Cystic epithelia were lined with thyroid follicular epithelium, exhibiting moderate atypia. Human bone marrow endothelial cell marker-1 and galectin-3 were focally positive; CK19 was positive in Case 1, and all 3 markers were positive in Case 2, previously reported as an immunophenotype of thyroid carcinoma. CD56 expression was positive in both cases. Targeted next-generation sequencing revealed several low-frequency mutations; however, no major driver alterations for thyroid cancer were detected. Adrenal cysts can be lined by thyroid follicular epithelium. Challenges arise in determining the malignant or benign nature of adrenal cysts.

The early-stage clinical course of anti-pituitary-specific transcription factor-1 hypophysitis diagnosed post-immune checkpoint inhibitor treatment: A case with review of literature.

Anti-pituitary-specific transcription factor-1 (PIT-1) hypophysitis, a paraneoplastic syndrome resulting from an autoimmune response against PIT-1, typically manifests with undetectable levels of growth hormone (GH) and prolactin (PRL), and significantly low levels of serum thyroid-stimulating hormone (TSH) at diagnosis. These hormonal levels are highly specific to this disease and serve as key diagnostic indicators. Herein, we present a detailed clinical course of a 69-year-old male with a history of gastric cancer and lymph node metastases who developed anti-PIT-1 hypophysitis after the initiation of immune checkpoint inhibitor (ICI) therapy, specifically nivolumab, oxaliplatin, and capecitabine. The patient was referred to our department owing to decreased TSH, free triiodothyronine (T3), and free thyroxine (T4) levels after two doses of nivolumab. Initially suspected as central hypothyroidism due to ICI-related hypophysitis, further assessment confirmed the diagnosis of anti-PIT-1 hypophysitis. Notably, GH, PRL, and TSH levels markedly declined, leading to complete deficiencies 2 months after the first nivolumab dose-a pattern consistent with that of previous cases of anti-PIT-1 hypophysitis. Therefore, this report not only presents an atypical subset of ICI-related hypophysitis but also delineates the process of hormone impairment leading to complete deficiencies in anti-PIT-1 hypophysitis. This case highlights the importance of vigilant monitoring for endocrine issues in patients undergoing ICI therapy, given the escalating incidence of immune-related adverse events associated with the extensive use of ICI therapy for various cancers.

Enteroblastic cholangiocarcinoma: An uncommon, underrecognized subtype of bile duct cancer.

Enteroblastic carcinoma is clinically characterized by an elevated serum level of alpha-fetoprotein (AFP) and is histologically characterized by cancer cells with a clear cytoplasm and 'blastic' coarse chromatin. It sometimes has an element of hepatoid carcinoma; therefore, these two neoplasms are often regarded as sister entities. Although hepatoid carcinoma in the biliary tree has been reported, enteroblastic cholangiocarcinoma is extremely uncommon. In the present study, four cases of enteroblastic cholangiocarcinoma were examined. Tumors were located inside the liver (n = 2) or common bile duct (n = 2). The two intrahepatic cases had a history of primary sclerosing cholangitis, and serum AFP levels were elevated in both. One unresectable case was diagnosed by needle liver biopsy, while the remaining three underwent surgical resection. Histologically, all cases showed similar microscopic features. Cuboidal or polygonal cancer cells with the characteristic clear cytoplasm and subnuclear vacuoles were arranged in a papillary, micropapillary, tubular, or solid architecture. One case had an element of pancreatobiliary-type adenocarcinoma, while a hepatoid carcinoma element was not observed in any cases. All cases were positive for AFP, glypican 3, and SALL4, with SALL4 being the most widely expressed. Heppar-1 and arginase-1 were negative, except for one case, which was positive for Heppar-1. In conclusion, enteroblastic cholangiocarcinoma is an uncommon subtype of biliary tract malignancy. These cases may have been categorized as 'clear cell' cholangiocarcinoma. Although enteroblastic cholangiocarcinoma seems to occur more commonly in extrahepatic regions, including the gallbladder, it may also develop in the liver, particularly in patients with primary sclerosing cholangitis.

Effects of the Cortisol Milieu on Tumor-Infiltrating Immune Cells in Corticotroph Tumors.

CONTEXT: Corticotrophs are susceptible to lymphocyte cytotoxicity, as seen in hypophysitis, suggesting that an immunological approach may be a potential strategy for corticotroph-derived tumors. OBJECTIVE: We aimed to clarify whether corticotroph tumors that induce hypercortisolemia (ACTHomas) could be targets for immunotherapy. METHODS: Tumor-infiltrating immune cells were immunohistochemically analyzed. ACTHomas were compared with other pituitary tumors, and further divided into 3 different cortisol-exposed milieus: Naïve (ACTHomas without preoperative treatment), Met (ACTHomas with preoperative metyrapone), and SCA (silent corticotroph adenomas). A 3-dimensional cell culture of resected tumors was used to analyze the effects of immune checkpoint inhibitors. RESULTS: The number of tumor-infiltrating lymphocytes (TILs) was low in ACTHomas. Among these, the number of CD8+ cells was lower in ACTHomas than in both somatotroph and gonadotroph tumors (both P < .01). Then we compared the differences in TILs among Naïve, Met, and SCA. The number of CD4+ cells, but not CD8+ cells, was higher in both Met and SCA than in Naïve. Next, we investigated tumor-associated macrophages, which could negatively affect T cell infiltration. The numbers of CD163+ and CD204+ cells were positively associated with cortisol levels. Moreover, tumor size was positively correlated with the number of CD204+ cells. CONCLUSION: We found the possibility that ACTHomas were immunologically cold in a cortisol-independent manner. In contrast, the tumor infiltration of CD4+ cells and M2-macrophages were associated with the cortisol milieu. Future studies are needed to validate these results and develop effective immunotherapy while considering the cortisol milieu.

Impact of intratumoral microbiome on tumor immunity and prognosis in human pancreatic ductal adenocarcinoma.

BACKGROUND: Recent evidence suggests that the presence of microbiome within human pancreatic ductal adenocarcinoma (PDAC) tissue potentially influences cancer progression and prognosis. However, the significance of tumor-resident microbiome remains unclear. We aimed to elucidate the impact of intratumoral bacteria on the pathophysiology and prognosis of human PDAC. METHODS: The presence of intratumoral bacteria was assessed in 162 surgically resected PDACs using quantitative polymerase chain reaction (qPCR) and in situ hybridization (ISH) targeting 16S rRNA. The intratumoral microbiome was explored by 16S metagenome sequencing using DNA extracted from formalin-fixed paraffin-embedded tissues. The profile of intratumoral bacteria was compared with clinical information, pathological findings including tumor-infiltrating T cells, tumor-associated macrophage, fibrosis, and alterations in four main driver genes (KRAS, TP53, CDKN2A/p16, SMAD4) in tumor genomes. RESULTS: The presence of intratumoral bacteria was confirmed in 52 tumors (32%) using both qPCR and ISH. The 16S metagenome sequencing revealed characteristic bacterial profiles within these tumors, including phyla such as Proteobacteria and Firmicutes. Comparison of bacterial profiles between cases with good and poor prognosis revealed a significant positive correlation between a shorter survival time and the presence of anaerobic bacteria such as Bacteroides, Lactobacillus, and Peptoniphilus. The abundance of these bacteria was correlated with a decrease in the number of tumor-infiltrating T cells positive for CD4, CD8, and CD45RO. CONCLUSIONS: Intratumoral infection of anaerobic bacteria such as Bacteroides, Lactobacillus, and Peptoniphilus is correlated with the suppressed anti-PDAC immunity and poor prognosis.

The combination of doxazosin and metyrosine as a preoperative treatment for pheochromocytomas and paragangliomas.

PURPOSE: Preoperative medical management is critical to prevent intraoperative cardiovascular complications in patients with pheochromocytomas and paragangliomas (PPGLs). Initial treatment involves α-adrenergic receptor blockers. However, while the routine use of metyrosine alongside these blockers is not strongly recommended due to a lack of evidence supporting its efficacy and associated safety concerns, there are previous studies on combination therapy with phenoxybenzamine and metyrosine. There are few reports on combination therapy with the selective α1-adrenergic receptor blocker doxazosin. Therefore, we investigated this combination treatment, which theoretically can affect perioperative outcomes in patients with PPGLs. To our knowledge, this is the first such study. METHODS: This retrospective single-center observational study involved 51 patients who underwent surgical resection of PPGLs at Kobe University Hospital between 2014 and 2022. All patients received doxazosin at maximum doses. Fourteen patients received concomitant metyrosine, while 37 received doxazosin alone. Their perioperative outcomes were compared. RESULTS: No severe event, such as acute coronary syndrome, was observed in either group. Intraoperatively, the doxazosin + metyrosine group exhibited a lower median minimum systolic blood pressure (56 [54-60] vs. 68 [59-74] mmHg, P = 0.03) and required lower median remifentanil (P = 0.04) and diltiazem (P = 0.02) doses than the doxazosin-alone group. CONCLUSION: The combination of metyrosine and doxazosin as a preoperative treatment for PPGLs affects intraoperative circulatory hemodynamics, such as a reduced occurrence of blood pressure elevation during surgery. Further research is necessary to identify patients who will benefit most from this combination treatment.

Amyloid deposition through endocytosis in vascular endothelial cells.

No mechanistic lead is known for establishing AL amyloid deposits in organs. We here report an electron microscopic (EM) analysis in a case of intestinal AL amyloidosis before initiating treatment for amyloidosis. The dense deposits of amyloid fibrils are concentrated around the small blood vessels in the submucosal area of intestinal tissue. Surprisingly, we observed endothelial cells (ECs) of blood vessels containing plenty of endocytotic (pinocytotic) and transcytotic vesicles at the luminal side and above the basement membrane, indicating the one-way active trafficking of either the immunoglobulin (Ig) light chain or preassembled amyloid fibrils from the luminal side of ECs to the extraluminal area of ECs. Immunoelectron microscopy displayed that the immuno-gold signals were observed in the vascular cavity and the subendothelial area of amyloid deposits. However, there is no sign of an Ig light chain in pinocytotic vesicles. Therefore, the intestinal ECs may actively pump out mainly the preassembled amyloid fibrils (not light chains) from the blood stream into the subendothelial area as a physiologic function.

Composite paraganglioma-ganglioneuroma with atypical catecholamine profile and phenylethanolamine N-methyltransferase expression: a case report and literature review.

Pheochromocytomas and paragangliomas (PPGLs) are rare tumors that secrete catecholamines and arise from the adrenal medulla or extra-adrenal sympathetic ganglia. These tumors secrete adrenaline and noradrenaline, but paragangliomas usually produce only noradrenaline because of the lack of phenylethanolamine N-methyltransferase (PNMT) expression. Composite paragangliomas, which are complex tumors consisting of multiple types of neuroblastic cells, are extremely rare. We present the case of a 46-year-old woman with an atypical catecholamine profile who was preoperatively diagnosed with pheochromocytoma. However, postoperative pathology revealed that the patient had an extra-adrenal paraganglioma accompanied by a ganglioneuroma, which led to the diagnosis of a composite tumor. Interestingly, PNMT is expressed in both paragangliomas and ganglioneuromas. In addition, we reviewed reported composite paragangliomas and compared their clinical features with those of composite pheochromocytomas. We also discuss various aspects of the etiology of composite paragangliomas and the mechanism by which PNMT is expressed in tumors.

Clinical features of anti-pituitary-specific transcription factor-1 (PIT-1) hypophysitis: a new aspect of paraneoplastic autoimmune condition.

The pathogenesis of anti-pituitary-specific transcription factor-1 (PIT-1) hypophysitis was gradually revealed as cases emerged. Our comprehensive analysis, including all reported cases, identified a new instance of anti-PIT-1 hypophysitis postimmune checkpoint inhibitor therapy. All 9 patients exhibited extremely low growth hormone (GH), prolactin (PRL), and thyroid-stimulating hormone (TSH) levels; 2 had a slightly atrophic pituitary gland; 4 had thymoma, and 5 had malignant neoplasms of diffuse large B-cell lymphoma (DLBCL) and other origins. Patients with thymoma showed multiple autoimmune diseases. HLA-A*24:02 and/or A*02:06 were present in six and DR53 in 5 cases analyzed. High anti-PIT-1 antibody titers and ectopic PIT-1 expression in the cytosol and nucleus of the tumor tissues were observed in patients with thymoma or DLBCL, whereas it was exclusively observed in the nuclei of a bladder cancer patient. These findings provide new insights into the pathophysiology of paraneoplastic autoimmune hypophysitis.

Colostomy-site carcinoma with primitive phenotype in a rectal cancer patient after achieving pathological complete response with neoadjuvant chemoradiotherapy.

Herein, we report a rare case of a carcinoma with primitive phenotype (enteroblastic and/or hepatoid differentiation) occurring at a colostomy site. The patient was an elderly male who underwent neoadjuvant chemoradiotherapy for rectal cancer, followed by abdominoperineal resection. A biopsy specimen for the rectal carcinoma before neoadjuvant chemoradiotherapy was conventional tubular adenocarcinoma. Moreover, a pathological complete response was confirmed in the proctectomy specimen. However, a colostomy-site tumor appeared 6 months after the proctectomy, and it was resected 1 year after the initial proctectomy. The colostomy-site tumor comprised solid to focal glandular growth of atypical polygonal cells with clear to pale eosinophilic cytoplasm and was immunohistochemically positive for cytokeratin, spalt-like transcription factor 4, glypican-3, caudal type homeobox 2, and special AT-rich sequence-binding protein 2. Thus, the tumor was diagnosed as poorly differentiated adenocarcinoma with primitive phenotype, with suggested origin from the colorectal epithelium. Additionally, a multilocular cystic lesion comprising various types of epithelia was found adjacent to the tumor, suggestive of metaplasia or heterotopia. Changes in the histology and immunophenotype, and the findings of an adjacent cystic lesion suggest a metachronous tumor rather than a recurrence of the primary tumor.

Paraneoplastic isolated adrenocorticotropic hormone deficiency revealed after immune checkpoint inhibitors therapy: new insights into anti-corticotroph antibody.

Introduction: A recently discovered facet of paraneoplastic adrenocorticotropic hormone (ACTH) deficiency exists in two forms: a paraneoplastic spontaneous isolated ACTH deficiency (IAD) and an immune checkpoint inhibitor (ICI)-related hypophysitis. Autoantibodies against corticotrophs, such as circulating anti-proopiomelanocortin (POMC) antibodies are considered disease markers. However, the number of identified cases was limited, implying that the characteristics of these autoantibodies are not fully understood. Methods: We investigate circulating autoimmune autoantibodies in detail through a novel case of IAD that developed as a paraneoplastic autoimmune ACTH deficiency. Results: The patient developed IAD after 25 weeks of ICI therapy for metastasis of large-cell neuroendocrine carcinoma at 69 years of age. Ectopic ACTH expression and infiltration of CD3+, CD4+, CD8+, and CD20+ lymphocytes were observed in the tumor tissues and circulating anti-POMC antibodies were detected specifically in the patient's serum. Moreover, detailed analyses of immunofluorescence staining using patient serum revealed that the recognition site of the autoantibody was ACTH25-39, which had not been identified in previous cases of paraneoplastic autoimmune ACTH deficiency. Conclusion: This case involved a combination of paraneoplastic spontaneously acquired IAD and ICI-related hypophysitis occupying the middle ground. Moreover, our study reveals new aspects of anti-POMC antibodies in patients with paraneoplastic ACTH deficiency. This report expands our understanding of the immunological landscape and provides new insights for the identification of antibodies associated with paraneoplastic autoimmune ACTH deficiency.

Use of Peroral Pancreatoscopy in the Diagnosis of Elusive Intraductal Papillary Mucinous Neoplasm With High-Grade Dysplasia.

Intraductal papillary mucinous neoplasm (IPMN) is a premalignant lesion of the pancreas that can occasionally manifest as recurrent acute pancreatitis. In this report, we discuss a unique case of a 49-year-old woman who presented with recurrent acute pancreatitis of an unknown cause for several years. Workup using peroral pancreatoscopy eventually showed main-duct IPMN with high-grade dysplasia as the obscure cause of recurrent acute pancreatitis. This case report highlights the clinical course of main-duct IPMN and the evolving role of peroral pancreatoscopy in patients with recurrent acute pancreatitis.

Benefits of pancreatic parenchymal endoscopic ultrasonography in predicting microscopic precancerous lesions of pancreatic cancer.

Pancreatic cancer primarily arises from microscopic precancerous lesions, such as pancreatic intraepithelial neoplasia (PanIN) and acinar-to-ductal metaplasia (ADM). However, no established method exists for predicting pancreatic precancerous conditions. Endoscopic ultrasonography (EUS) can detect changes in pancreatic parenchymal histology, including fibrosis. This study aimed to elucidate the relationship between pancreatic parenchymal EUS findings and microscopic precancerous lesions. We retrospectively analyzed 114 patients with pancreatobiliary tumors resected between 2010 and 2020 and evaluated the association between pancreatic parenchymal EUS findings and the number of PanIN, ADM, and pancreatic duct gland (PDG). Of the 114 patients, 33 (29.0%), 55 (48.2%), and 26 (22.8%) had normal EUS findings, hyperechoic foci/stranding without lobularity, and hyperechoic foci/stranding with lobularity, respectively. Multivariate analyses revealed that abnormal EUS findings were significantly associated with the frequency of PanIN (hyperechoic foci/stranding without lobularity: OR [95% CI] = 2.7 [1.0-7.3], with lobularity: 6.5 [1.9-22.5], Ptrend = 0.01) and ADM (hyperechoic foci/stranding without lobularity: 3.1 [1.1-8.2], with lobularity: 9.7 [2.6-36.3], Ptrend = 0.003) but not with PDG (hyperechoic foci/stranding without lobularity: 2.2 [0.8-5.8], with lobularity: 3.2 [1.0-10.2], Ptrend = 0.12). We observed a trend toward a significantly higher number of precancerous lesions in the following order: normal findings, hyperechoic foci/stranding without lobularity, and hyperechoic foci/stranding with lobularity. Pancreatic parenchymal EUS findings were associated with the increased frequency of PanIN and ADM. Lobularity may help predict the increased number of precancerous lesions.

A comprehensive analysis of tumor-stromal collagen in relation to pathological, molecular, and immune characteristics and patient survival in pancreatic ductal adenocarcinoma.

BACKGROUND: Abundant collagen deposition is a hallmark of pancreatic ductal adenocarcinomas (PDACs). This study clarified the interactive relationship between tumor-stromal collagen, molecular and immune characteristics, and tumor pr ogression in human PDAC. METHODS: We performed a comprehensive examination using an integrative molecular pathological epidemiology database on 169 cases with resected PDAC . The amount of tumor-stromal collagen was quantified through digital imaging analysis for Elastica van Gieson-stained whole-section tumor slides. We analyzed the association of tumor-stromal collagen with gene alterations (KRAS, TP53, CDKN2A/p16, and SMAD4), immune parameters (CD4+ tumor-infiltrating lymphocytes [TILs], CD8+ TILs, FOXP3+ TILs, and tertiary lymphoid structures), and patient prognosis. RESULTS: Low amounts of tumor-stromal collagen were associated with poor differentiation (multivariable OR = 3.82, 95%CI = 1.41-12.2, P = 0.008) and CDKN2A/p16 alteration (OR [95%CI] = 2.06 [1.08-4.02], P = 0.03). Tumors with low collagen levels had shorter overall survival (HR [95%CI] = 2.38 [1.59-3.56], P < 0.0001). In the S-1 and gemcitabine (GEM) treatment groups, low tumor-stromal collagen was linked to poor prognosis of patients with PDAC (S-1 group: multivariable HR [95%CI] = 2.76 [1.36-5.79], P = 0.005; GEM group: multivariate HR [95%CI] = 2.91 [1.34-6.71], P = 0.007). Additionally, low amounts of tumor-stromal collagen were also linked to low levels of CD4+ TILs (P = 0.046), CD8+ TILs (P = 0.09), and tertiary lymphoid structures (P = 0.001). CONCLUSIONS: Tumor-stromal collagen deposition may play a crucial role in modulating tumor-immune microenvironment and determining response to adjuvant chemotherapy and patient survival outcomes.

Association of Sarcopenia with a Poor Prognosis and Decreased Tumor-Infiltrating CD8-Positive T Cells in Pancreatic Ductal Adenocarcinoma: A Retrospective Analysis.

BACKGROUND: Sarcopenia, defined as a loss of skeletal muscle mass and quality, is found in 30-65% of patients with pancreatic ductal adenocarcinoma (PDAC) at diagnosis, and is a poor prognostic factor. However, it is yet to be evaluated why sarcopenia is associated with poor prognosis. Therefore, this study elucidated the tumor characteristics of PDAC with sarcopenia, including driver gene alterations and tumor microenvironment. PATIENTS AND METHODS: We retrospectively analyzed 162 patients with PDAC who underwent pancreatic surgery between 2008 and 2017. We defined sarcopenia by measuring the skeletal muscle mass at the L3 level using preoperative computed tomography images and evaluated driver gene alteration (KRAS, TP53, CDKN2A/p16, and SMAD4) and tumor immune (CD4+, CD8+, and FOXP3+) and fibrosis status (stromal collagen). RESULTS: In localized-stage PDAC (stage ≤ IIa), overall survival (OS) and recurrence-free survival were significantly shorter in the sarcopenia group than in the non-sarcopenia group (2-year OS 89.7% versus 59.1%, P = 0.03; 2-year RFS 74.9% versus 50.0%, P = 0.02). Multivariate analysis revealed that sarcopenia was an independent poor prognostic factor in localized-stage PDAC. Additionally, tumor-infiltrating CD8+ T cells in the sarcopenia group were significantly less than in the non-sarcopenia group (P = 0.02). However, no difference was observed in driver gene alteration and fib.rotic status. These findings were not observed in advanced-stage PDAC (stage ≥ IIb). CONCLUSIONS: Sarcopenia was associated with a worse prognosis and decreased tumor-infiltrating CD8+ T cells in localized-stage PDAC. Sarcopenia may worsen a patient's prognosis by suppressing local tumor immunity.

Integrated analysis of tertiary lymphoid structures in relation to tumor-infiltrating lymphocytes and patient survival in pancreatic ductal adenocarcinoma.

BACKGROUND: Tertiary lymphoid structure (TLS) reflects an intense immune response against cancer, which correlates with favorable patient survival. However, the association of TLS with tumor-infiltrating lymphocytes (TILs) and clinical outcomes has not been investigated comprehensively in pancreatic ductal adenocarcinoma (PDAC). METHODS: We utilized an integrative molecular pathological epidemiology database on 162 cases with resected PDAC, and examined TLS in relation to levels of TILs, patient survival, and treatment response. In whole-section slides, we assessed the formation of TLS and conducted immunohistochemistry for tumor-infiltrating T cells (CD4, CD8, CD45RO, and FOXP3). As confounding factors, we assessed alterations of four main driver genes (KRAS, TP53, CDKN2A [p16], and SMAD4) using next-generation sequencing and immunohistochemistry, and tumor CD274 (PD-L1) expression assessed by immunohistochemistry. RESULTS: TLSs were found in 112 patients with PDAC (69.1%). TLS was associated with high levels of CD4+ TILs (multivariable odds ratio [OR], 3.50; 95% confidence interval [CI] 1.65-7.80; P = 0.0002), CD8+ TILs (multivariable OR, 11.0; 95% CI 4.57-29.7, P < 0.0001) and CD45RO+ TILs (multivariable OR, 2.65; 95% CI 1.25-5.80, P = 0.01), but not with levels of FOXP3+ TILs. TLS was associated with longer pancreatic cancer-specific survival (multivariable hazard ratio, 0.37; 95% CI 0.25-0.56, P < 0.0001) and favorable outcomes of adjuvant S-1-treatment. TLS was not associated with driver gene alterations but tumor CD274 negative expression. CONCLUSIONS: Our comprehensive data supports the surrogacy of TLS for vigorous anti-tumor immune response characterized by high levels of helper and cytotoxic T cells and their prognostic role.

Lobularity rather than hyperechoic foci/stranding on endoscopic ultrasonography is associated with more severe histological features in chronic pancreatitis.

BACKGROUND AND AIM: Endoscopic ultrasonography (EUS) findings of the pancreatic parenchyma, such as hyperechoic foci/stranding and lobularity, may be associated with the severity of chronic pancreatitis (CP). However, the correlation between parenchymal EUS findings and histology remains unclear. We designed a large-scale retrospective study analyzing over 200 surgical specimens to elucidate the association between parenchymal EUS findings and histological features. METHODS: Clinical data of 221 patients with pancreatobiliary tumors who underwent preoperative EUS and pancreatic surgery between January 2010 and November 2020 were reviewed to investigate the association between parenchymal EUS findings and histological features at the pancreatic body. None of these patients met the definition of CP. RESULTS: Of the 221 patients, 87 (39.4%), 89 (40.2%), and 45 (20.4%) had normal EUS findings, hyperechoic foci/stranding without lobularity, and hyperechoic foci/stranding with lobularity, respectively. In the multivariate analyses, parenchymal EUS findings significantly correlated with histological CP findings of fibrosis, inflammation, and atrophy (hyperechoic foci/stranding without lobularity vs hyperechoic foci/stranding with lobularity, odds ratio [95% confidence interval]: 4.1 [2.2-7.9] vs 31.3 [9.3-105.6], Ptrend  < 0.001; 3.9 [1.9-8.2] vs 21.8 [8.0-59.4], Ptrend  < 0.001; and 4.0 [2.0-7.8] vs 22.9 [7.0-74.5], Ptrend  < 0.001, respectively). Further, a trend toward higher histological grade was observed in the following order: normal findings, hyperechoic foci/stranding without lobularity, and hyperechoic foci/stranding with lobularity. CONCLUSIONS: Endoscopic ultrasonography findings of the pancreatic parenchyma may be associated with the histological conditions in CP, such as pancreatic fibrosis, inflammation, and atrophy. Lobularity reflects more severe histological conditions than does hyperechoic foci/stranding.