Shi, Jiaqi

Abstract Pancreatic ductal adenocarcinoma (PDAC), the most common subtype of pancreatic cancer, is a deadly disease with a complex tumor microenvironment (TME). Cytotoxic combination chemotherapy treatments are the mainstay of PDAC therapy, but patients rapidly develop chemoresistance, highlighting the need to elucidate how chemotherapy alters the TME and whether these changes drive chemoresistance. Here, we examined matched pre- and post-treatment tissue specimens using single-cell RNA-sequencing and found near-universal enrichment after treatment of axonal guidance genes in cancer-associated fibroblasts (CAFs). These neural CAFs were enriched near sites of perineural invasion, coinciding with regions of increased tumor cell proliferation, and were enriched in tumor areas distant from nerves after chemotherapy. Metastatic recurrent lesions had the highest prevalence of neural CAFs versus primary tumors and untreated metastases. Neural CAFs showed elevated non-canonical WNT mediators and axonal guidance genes, which complemented matching cognate binding partners in tumor epithelial cells, suggesting a role in tumor-stroma crosstalk. Additionally, in vitro studies revealed enrichment of axonal guidance genes in patient-derived CAF lines upon exposure to chemotherapy or tumor cells. Altogether, these findings implicate fibroblast-derived axonal-guidance genes in promoting PDAC invasion and point to a promising therapeutic target for this disease.

Abstract Pancreatic ductal adenocarcinoma (PDAC), the most common subtype of pancreatic cancer, is a deadly disease with a complex tumor microenvironment (TME). How chemotherapy alters the TME, and whether these changes drive chemoresistance, is poorly understood. We examined matched pre- and post-treatment tissue specimens and found near-universal enrichment of axonal guidance genes in cancer-associated fibroblasts (CAFs) after treatment. These CAFs were enriched near sites of perineural invasion, coinciding with regions of increased tumor cell proliferation, and were enriched in tumor areas distant from nerves after chemotherapy. Metastatic recurrence lesions had the highest prevalence of these CAFs versus primary tumors and untreated metastasis. These CAFs showed elevated non-canonical Wnt mediators and axonal guidance genes, which complemented matching cognate binding partners in tumor epithelial cells, suggesting a role in tumor-stroma crosstalk. Our findings implicate fibroblast-derived axonal-guidance genes in promoting PDAC invasion and point to a promising target for this disease. Statement of Significance Therapeutic resistance remains a major challenge in pancreatic cancer. Our findings shed light on the changes in the complex tumor microenvironment in response to chemotherapy and identify fibroblasts high in axonal-guidance genes that may drive tumor progression and chemoresistance, thus uncovering a potential avenue for targeting pancreatic cancer.

Pancreatic cancer is a malignancy arising from the endocrine or exocrine compartment of this organ. Tumors from exocrine origin comprise over 90% of all pancreatic cancers diagnosed. Of these, pancreatic ductal adenocarcinoma (PDAC) is the most common histological subtype. The five-year survival rate for PDAC ranged between 5 and 9% for over four decades, and only recently saw a modest increase to ∼12–13%, making this a severe and lethal disease. Like other cancers, PDAC initiation stems from genetic changes. However, therapeutic targeting of PDAC genetic drivers has remained relatively unsuccessful, thus the focus in recent years has expanded to the non-genetic factors underlying the disease pathogenesis. Specifically, it has been proposed that dynamic changes in the epigenetic landscape promote tumor growth and metastasis. Emphasis has been given to the re-organization of enhancers, essential regulatory elements controlling oncogenic gene expression, commonly marked my histone 3 lysine 4 monomethylation (H3K4me1). H3K4me1 is typically deposited by histone lysine methyltransferases (KMTs). While well characterized as oncogenes in other cancer types, recent work has expanded the role of KMTs as tumor suppressor in pancreatic cancer. Here, we review the role and translational significance for PDAC development and therapeutics of KMTs.

Currently, there are no internationally accepted consensus guidelines for pathologic evaluation of posttherapy pancreatectomy specimens. The Neoadjuvant Therapy Working Group of Pancreatobiliary Pathology Society was formed in 2018 to review grossing protocols, literature, and major issues and to develop recommendations for pathologic evaluation of posttherapy pancreatectomy specimens. The working group generated the following recommendations: (1) Systematic and standardized grossing and sampling protocols should be adopted for pancreatectomy specimens for treated pancreatic ductal adenocarcinoma (PDAC). (2) Consecutive mapping sections along the largest gross tumor dimension are recommended to validate tumor size by histology as required by the College of American Pathologists (CAP) cancer protocol. (3) Tumor size of treated PDACs should be measured microscopically as the largest dimension of tumor outer limits that is bound by viable tumor cells, including intervening stroma. (4) The MD Anderson grading system for tumor response has a better correlation with prognosis and better interobserver concordance among pathologists than does the CAP system. (5) A case should not be classified as a complete response unless the entire pancreas, peripancreatic tissues, ampulla of Vater, common bile duct, and duodenum adjacent to the pancreas are submitted for microscopic examination. (6) Future studies on tumor response of lymph node metastases, molecular and/or immunohistochemical markers, as well as application of artificial intelligence in grading tumor response of treated PDAC are needed. In summary, systematic, standardized pathologic evaluation, accurate tumor size measurement, and reproducible tumor response grading to neoadjuvant therapy are needed for optimal patient care. The criteria and discussions provided here may provide guidance towards these goals.

AimsAdenomatoid tumours are mesothelial‐derived benign neoplasms with a predilection for the genital tract. Extragenital sites are rare and can cause significant diagnostic challenges. Herein, we describe the clinicopathological features of a cohort of adenomatoid tumours involving the gastrointestinal tract and liver in order to more clearly characterise their histological findings and aid in diagnosis.Methods and resultsThe pathology databases at four institutions were searched for adenomatoid tumours involving the gastrointestinal tract or liver, yielding eight cases. Available clinicoradiological and follow‐up data were collected from the medical records. Six tumours were incidentally discovered during imaging studies or at the time of surgical exploration for unrelated conditions; presenting symptoms were unknown in two patients. Histologically, the tumours were well‐circumscribed, although focal ill‐defined borders were present in four cases. No infiltration of adjacent structures was identified. Architectural heterogeneity was noted in five (63%) tumours; an adenoid pattern often predominated. The neoplastic cells were flattened to cuboidal with eosinophilic cytoplasm. Cytoplasmic vacuoles mimicking signet ring‐like cells were present in five (63%) cases. Three (38%) cases showed involvement of the mesothelium with reactive mesothelial hyperplasia. Cytological atypia or increased mitotic activity was not identified. The surrounding stroma ranged from oedematous/myxoid to densely hyalinised. Immunohistochemistry confirmed mesothelial origin in all cases evaluated. No patients developed recurrence of disease.ConclusionsThe current study evaluates the clinicopathological findings in a collective series of gastrointestinal and hepatic adenomatoid tumours, correlating with those described in individually reported cases. We highlight common histological features and emphasise variable findings that could mimic a malignant neoplasm.

Background Pancreatoblastoma (PBL) is a rare malignant pancreatic tumor seen predominantly in childhood, and its cytologic diagnosis remains challenging. Methods Twelve fine‐needle‐aspirations from 11 adults were analyzed. Results In total, 6 men and 5 women (median age, 45 years; age range, 32‐60 years) had tumors measuring a median 5.6 cm (range, 2.5‐12 cm) located in the pancreatic head (n = 7) or tail (n = 4), including 3 with familial adenomatous polyposis (FAP)/FAP‐related syndromes and 4 with metastasis at diagnosis. The median follow‐up was 39.8 months (range, 0.8‐348 months), and 5 patients died of disease. The original cytology diagnoses were: PBL (n = 2), neuroendocrine neoplasm (n = 2), poorly differentiated neuroendocrine carcinoma (n = 2), well differentiated neuroendocrine tumor (n = 1), poorly differentiated carcinoma (n = 2), “positive for malignancy” (n = 1), acinar cell carcinoma (n = 1), and epithelioid neoplasm with endocrine and acinar differentiation versus PBL (n = 1). Universal cytopathologic findings included hypercellularity; 3‐dimensional clusters; and single, monotonous, blast‐like cells that were from 1.5 to 2.0 times the size of red blood cells with high nuclear‐to‐cytoplasmic ratio, fine chromatin, small, distinct nucleoli, and a resemblance to well differentiated neuroendocrine tumor and poorly differentiated neuroendocrine carcinoma. Branching pseudopapillae (n = 7) and grooved nuclei (n = 3) raised the differential diagnosis of solid‐pseudopapillary neoplasm, but with more atypia. Uncommon features included pleomorphism (n = 4) and numerous mitoses (n = 1). Squamoid morules were seen on smears (n = 5) or cell blocks (n = 6) in 70% of patients and were characterized by epithelioid cells with elongated, streaming nuclei, fine chromatin, absent nucleoli, and positive nuclear β‐catenin (n = 6 of 8). The median Ki‐67 index was 21% (range, 2%‐70%), and neuroendocrine marker expression was common (100%), but acinar markers were variable (63%). Conclusions A combination of cytologic findings in PBL, including a predominant population of primitive blast‐like cells, subtle squamoid morules, frequent neuroendocrine and variable acinar phenotype, should facilitate accurate cytologic diagnosis and distinction from common mimics.

BackgroundHepatocellular carcinoma (HCC) rarely involves the biliary tree and may be inadvertently sampled on bile duct brushings (BDBs).MethodsThe pathology archives of 5 institutions were searched for BDBs with HCC involvement.ResultsA total of 17 BDBs from 14 patients were obtained. There was a male:female ratio of 6:1; the median age of the patients was 59.5 years (range, 22‐80 years). The median hepatic tumor size was 6.2 cm (range, 2.2‐13.0 cm). HCC risk factors included viral hepatitis (5 patients), cirrhosis (5 patients), hemochromatosis (1 patient), and alcoholic steatohepatitis (1 patient). Jaundice with elevated bilirubin, liver enzymes, and α‐fetoprotein was common. Endoscopic retrograde cholangiopancreatography demonstrated bile duct dilatation, polypoid intraductal masses (5 samples), clots/debris (2 samples), or strictures (4 samples). All BDBs had single and clustered large cells with naked atypical nuclei, granular cytoplasm, high nuclear/cytoplasmic ratios, and nuclei with prominent macronucleoli. Less common findings included clear/microvesicular cytoplasm (35%), papillae (29%), and anisonucleosis (35%). Classic HCC features (widened trabeculae [35%], endothelial wrapping [24%], multinucleation [24%], and cytoplasmic bile pigment [35%]) were uncommon. A total of 11 BDBs were diagnosed as malignant (10 with HCC and 1 with cholangiocarcinoma), 2 were diagnosed as atypical, and 1 BDB was diagnosed as negative; approximately two‐thirds were found to have polysomy on fluorescence in situ hybridization. Approximately 71% of patients died of disease at a median of 3.5 months.ConclusionsHCC may extend into the intrahepatic and/or extrahepatic biliary tree, causing masses and/or strictures that may be sampled on BDB. Although cytologically malignant, the classic features of HCC are uncommon, which can cause misdiagnosis. Cytopathologists should be mindful of this differential when evaluating BDBs, particularly when concomitant liver masses and/or HCC risk factors are present. Because of the associated high mortality and rapid rate of death, its presence should be conveyed clearly in pathology reports.

BACKGROUNDThe cytologic features of undifferentiated pancreatic carcinoma with osteoclastic giant cells (UOC) are rarely described.METHODSCytologic and clinicopathologic characteristics in 15 UOC fine‐needle aspiration (FNA) specimens were analyzed.RESULTSFNA specimens were obtained from 6 men and 8 women with a mean age of 65 years who had UOCs (head, n = 7; body, n = 3; and tail, n = 4) with a mean radiologic size 7.3 cm, and some had a cystic component (n = 9). Three cell types (osteoclastic giant cells, pleomorphic tumor giant cells, and spindled/histiocytoid cells) were observed in 12 of 15 specimens (80%); and pancreatic ductal adenocarcinoma (PDAC) was present in 11 specimens. FNA diagnoses were UOC (n = 6), PDAC (n = 5), poorly differentiated carcinoma (n = 2), “suspicious for neoplasm” (n = 1), and “negative” (n = 1). Five of 5 specimens with osteoclastic giant cells were positive for cluster of differentiation 68 (CD68) (a glycoprotein that binds to low‐density lipoprotein). Pleomorphic tumor giant cells and spindled/histiocytoid cells were positive for pancytokeratin (6 of 7 specimens), CAM5.2 (2 of 3 specimens), and epithelial membrane antigen (2 of 2 specimens). INI‐1 protein expression was retained in 3 of 3 specimens. The Ki‐67 labeling index was assessed in 3 specimens and was 12%, 18%, and 40%; 4 of 12 resected UOCs were pure, and 8 were mixed with PDAC. One resection specimen had intraductal papillary mucinous neoplasm, and 2 had mucinous cystic neoplasms. The median overall survival (OS) of patients who had UOCs identified on FNA was 8 months (6 died [OS, 8 months; range, 2‐22 months], and 8 remained alive [OS, 3 months; range, 1‐27 months]), which was similar to the survival of 74 patients who had PDACs identified on FNA (OS, 15 months; P = .279) but worse than that of the 27 patients with UOCs who did not undergo FNA (OS, 92 months; P = .0135).CONCLUSIONSThe 3 classical UOC cell types are identifiable on FNA, making cytologic diagnosis possible if considered in the differential. A PDAC component is often also observed. The survival advantage of UOC over pure PDAC appears to be negated by FNA and requires further investigation. Cancer Cytopathol 2017;125:563–75. © 2017 American Cancer Society.