Prognostic performance of microscopic size measurements in small invasive carcinomas arising in intraductal papillary mucinous neoplasms of the pancreas.

AIMS: Small invasive carcinomas arising in intraductal papillary mucinous neoplasms (IPMNs) of the pancreas can present as multiple, small foci. In such cases, there is no clear optimal measurement method for determining the invasive size for tumour staging and prognostication. METHODS: In all, 117 small invasive IPMNs (size of largest invasive component ≤2 cm) from seven institutions (2000-2016) were reviewed, and all individual foci of invasive carcinoma were measured. T stages (AJCC 8th edition) based on the largest single focus size (LS), average size of all foci (AS), and total sum of all foci (TS) were examined in association with clinicopathologic parameters and patient outcomes. RESULTS: The cohort comprised IPMNs with invasive tubular-type (n = 82, 70%) and colloid-type (n = 35, 30%) carcinomas. The mean LS, AS, and TS were 0.86, 0.71, and 1.32 cm, respectively. Based on the LS, AS, and TS, respectively, 48, 65, and 39 cases were classified as pT1a; 22, 18, and 11 cases as pT1b; and 47, 34, and 50 cases as pT1c. Higher pT stages based on all measurements were significantly associated with small vessel, large vessel, and perineural invasion (P < 0.05). LS-, AS-, and TS-based pT stages were not significantly associated with recurrence-free survival (RFS) or overall survival (OS) by univariate or multivariate analyses. However, among tubular-type carcinomas, higher LS-, AS-, and TS-based pT stages trended with lower RFS (based on 1-, 3-, and 5-year survival rates). All microscopic measurement methods were most predictive of RFS and OS using a 1.5-cm cutoff, with LS significantly associated with both RFS and OS by univariate and multivariate analysis. CONCLUSIONS: For invasive tubular-type carcinomas arising in IPMN, microscopic size-based AJCC pT stages were not significant predictors of patient outcomes. However, for LS, a size threshold of 1.5 cm was optimal for stratifying both RFS and OS. The AJCC 8th ed. may not be applicable for stratifying small invasive IPMNs with colloid-type histology that generally portend a more favourable prognosis.

Acute and Chronic Alcoholic Pancreatitis, Including Paraduodenal Pancreatitis.

CONTEXT.­: In the last 2 decades there has been significant progress in typing and recognition of pancreatitis, a necroinflammatory and fibroinflammatory process of multifactorial origin. OBJECTIVE.­: To present the current state of pathology and pathogenesis of alcohol-associated pancreatitis, including paraduodenal pancreatitis. In the context of the most important epidemiologic, clinical, and radiologic features, the related macroscopic changes and histopathologic characteristics are addressed. DATA SOURCES.­: In acute pancreatitis we discuss the pathologic findings that distinguish mild from severe pancreatitis and highlight autodigestive fat necrosis as the initial morphologic damage. In chronic pancreatitis we present a histologic staging system that describes the damage patterns as a necrosis-fibrosis sequence that takes place during the development of early to advanced and end-stage chronic pancreatitis. In paraduodenal pancreatitis the anatomic peculiarities are related to the sequence of morphologic changes that are correlated to the most important imaging findings. Pathogenetically, we discuss the role of alcohol overconsumption in triggering autodigestive fat necrosis in the pancreas, the repair of which results in a pancreas-transforming fibroinflammatory process. CONCLUSIONS­: Whereas in acute pancreatitis there are no lesions that are diagnostic for alcohol overconsumption and that exclude other etiologies such as gallstone disease or drugs, the sequence of damage patterns in chronic pancreatitis are strongly related to the effect of alcohol overconsumption and allow in many cases the distinction from hereditary, autoimmune, or obstructive pancreatitis. Paraduodenal pancreatitis can be considered a special manifestation of alcoholic pancreatitis.

Comparison of three validated PD-L1 immunohistochemical assays in urothelial carcinoma of the bladder: interchangeability and issues related to patient selection.

Different programmed cell death-ligand 1 (PD-L1) assays and scoring algorithms are being used in the evaluation of PD-L1 expression for the selection of patients for immunotherapy in specific settings of advanced urothelial carcinoma (UC). In this paper, we sought to investigate three approved assays (Ventana SP142 and SP263, and Dako 22C3) in UC with emphasis on implications for patient selection for atezolizumab/pembrolizumab as the first line of treatment. Tumors from 124 patients with invasive UC of the bladder were analyzed using tissue microarrays (TMA). Serial sections were stained with SP263 and SP142 on Ventana Benchmark Ultra and with 22C3 on Dako Autostainer Link 48. Stains were evaluated independently by two observers and scored using the combined positive score (CPS) and tumor infiltrating immune cells (IC) algorithms. Differences in proportions (DP), overall percent agreement (OPA), positive percent agreement (PPA), negative percent agreement (NPA), and Cohen κ were calculated for all comparable cases. Good overall concordance in analytic performance was observed for 22C3 and SP263 with both scoring algorithms; specifically, the highest OPA was observed between 22C3 and SP263 (89.6%) when using CPS. On the other hand, SP142 consistently showed lower positivity rates with high differences in proportions (DP) compared with 22C3 and SP263 with both CPS and IC, and with a low PPA, especially when using the CPS algorithm. In conclusion, 22C3 and SP263 assays show comparable analytical performance while SP142 shows divergent staining results, with important implications for the selection of patients for both pembrolizumab and atezolizumab.

Pancreatic metastases after surgery for renal cell carcinoma: survival and pathways of progression.

PURPOSE: Metastatic ccRCC has peculiar tropism in the pancreas. We describe the characteristics and pathways of progression of patients with PM in a large multi-institutional consortium and compare them to patients with metastases from ccRCC at other sites. METHODS: Detailed clinical and histopathological data were collected. To account for differences in baseline characteristics between the two groups, IPTW was used to compare the two groups in terms of PFS and OS. RESULTS: Of the 182 patients, 33 (18%) had pancreatic, 94 (52%) pulmonary, 30 (16%) bone, 13 (7%) hepatic, and 12 (7%) brain metastases. Patients with PM had less aggressive ccRCC at baseline compared to those with progression at other sites in terms of tumour stage and grade. Median time from ccRCC surgery to PM was 8 (95%CI 5-10) vs. 1 year (95%CI 1-2) for progression to other sites (p < 0.001). Median IPTW-weighted time to second progression was 4.3 years (95%CI 2.4-not reached) for patients with PM vs 1.1 year (95%CI 0.8-2.3) for those with progression in other sites (p < 0.001). The most frequent second progression sites were pancreas (24%) and liver (15%) in patients with PM, while progression to the pancreas was rare (4%) in those with a different first progression site. Surgery alone (55%) or in combination with medical therapy (30%) was more frequent in the PM group than in other sites (p < 0.001). Median IPTW-OS time was longer for patients with PM [8.8 years (95%CI 6.5-not reached)] compared to those with first progression in other sites [2.8 years (95%CI 1.9-4.3), p < 0.001]. CONCLUSION: Pancreatic tropism is typical of ccRCC tumours with more indolent behaviour than those progressing to other sites. A long follow-up period is necessary to distinguish PM from ccRCC.

Implications of Perineural Invasion on Disease Recurrence and Survival After Pancreatectomy for Pancreatic Head Ductal Adenocarcinoma.

OBJECTIVE: To describe PNI and to evaluate its impact on disease-free (DFS) and overall survival (OS) in patients with resected pancreatic ductal adenocarcinoma (PDAC). SUMMARY OF BACKGROUND DATA: Although PNI is a prognostic factor for survival in many GI cancers, there is limited knowledge regarding its impact on tumor recurrence, especially in ''early stage disease'' (PDAC ≤20 mm, R0/ N0 PDAC). METHODS: This multicenter retrospective study included patients undergoing PDAC resection between 2009 and 2014. The association of PNI with DFS and OS was analyzed using Cox proportional-hazards models. RESULTS: PNI was found in 87% of 778 patients included in the study, with lower rates in PDAC ≤20 mm (78.7%) and in R0/N0 tumors (70.6%). PNI rate did not differ between patients who underwent neoadjuvant therapy and upfront surgery (88% vs 84%, P = 0.08). Although not significant at multivariate analysis ( P = 0.07), patients with PNI had worse DFS at univariate analysis (median DFS: 20 vs 15 months, P < 0.01). PNI was the only independent predictor of DFS in R0/N0 tumors (hazard ratio [HR]: 2.2) and in PDAC ≤ 20 mm (HR: 1.8). PNI was an independent predictor of OS in the entire cohort (27 vs 50 months, P = 0.01), together with G3 tumors, pN1 status, carbohydrate antigen (CA) 19.9 >37 and pain. CONCLUSIONS: PNI represents a major determinant of tumor recurrence and patients' survival in pancreatic cancer. The role of PNI is particularly relevant in early stages, supporting the hypothesis that invasion of nerves by cancer cells has a driving role in pancreatic cancer progression.

TSC loss is a clonal event in eosinophilic solid and cystic renal cell carcinoma: a multiregional tumor sampling study.

Eosinophilic, solid and cystic (ESC) renal cell carcinoma (RCC) is characterized by a solid and cystic architecture with cells showing abundant eosinophilic cytoplasm with hobnail arrangement and a cytokeratin 7-negative/cytokeratin 20-positive immunophenotype. Recent studies have suggested that bi-allelic events affecting TSC genes might play an important role for such tumors. However, only indirect evidence of the clonal origin of TSC mutation has been gathered so far. Therefore, in this paper we aimed to perform multi-regional tumor sampling molecular analysis in four ESC RCC cases that had been completely embedded, three sporadic and one occurring in a patient with tuberous sclerosis complex (TSC). Histologically, the 4 cases showed cystic and solid architecture and cells with abundant eosinophilic cytoplasm with cytoplasmic stippling and round to oval nuclei. Immunohistochemistry showed at least focal expression of cytokeratin 20 in all tissue samples and negative cytokeratin 7, as well as diffuse positivity for S100A1 and at least focal expression of cathepsin K in three out of four cases. The sporadic cases showed the same somatic TSC1 mutations in all tissue samples analyzed, while the TSC-associated case showed the same TSC1 alteration in both normal tissue and all tumor samples analyzed, proving the germline nature of the alteration. In conclusion, our data demonstrate that clonal TSC loss is a key event in ESC RCC and support considering ESC RCC as an entity given its distinct morphologic, immunophenotypical and molecular characteristics.

Main Duct Thresholds for Malignancy Are Different in Intraductal Papillary Mucinous Neoplasms of the Pancreatic Head and Body-Tail.

BACKGROUND & AIMS: The risk of malignancy is uncertain for intraductal papillary mucinous neoplasms (IPMNs) with main pancreatic duct (MPD) of 5-9 mm. No study has correlated MPD size and malignancy considering the anatomic site of the gland (head versus body-tail). Our aim was to analyze the significance of MPD in pancreatic head/body-tail as a predictor of malignancy in main-duct/mixed IPMNs. METHODS: Retrospective analysis of resected patients between 2009-2018 was performed. Malignancy was defined as high-grade dysplasia and invasive carcinoma. MPD diameter was measured with magnetic resonance imaging. Receiver operating characteristic curve (ROC) analysis was utilized to identify optimal MPD cut-off for malignancy. Independent predictors of malignancy were searched. RESULTS: Malignancy was detected in 74% of 312 identified patients. 213 patients (68.3%) had IPMNs of the pancreatic head and 99 (31.7%) of the body-tail. ROC analysis identified 9 and 7 mm as the optimal MPD cut-offs for malignancy in IPMNs of head and body-tail of the pancreas, respectively. Multivariate analysis confirmed that MPD ≥9 mm (pancreatic head) and ≥7 mm (body-tail) were independent predictors of malignancy along with macroscopic solid components, positive cytology and elevated CA 19-9. The risk of malignancy was low for IPMNs with MPD ≤8 mm (pancreatic head) or ≤6 mm (pancreatic body-tail) unless high-risk stigmata or multiple worrisome features were present. CONCLUSIONS: Different thresholds of MPD dilation are associated with malignancy in IPMNs of the head and body-tail of the pancreas. The risk of malignancy for IPMNs with MPD ≤8 mm (pancreatic head) or ≤6 mm (pancreatic body-tail) lacking high-risk stigmata or multiple worrisome features is low.

Epithelioid angiomyolipoma: a pathological entity discovered in Verona with the endorsement of Doctor Rosai.

In this manuscript, we summarize the main features of angiomyolipoma highlighting the recognition of epithelioid angiomyolipoma and the discovery of immunohistochemical expression of HMB45 in a group of tumors that now are referred to as as PEComas. In this scenario, Dr. Rosai believed in our intuition, demonstrating his intellectual honesty and motivated us with his experience ("when a tumor seems malignant it is malignant") and enthusiasm for the new entities ("in Verona, you use HMB45 instead of H&E"). He really pushed the improvement of the knowledge in this field.

Pituitary metastases from neuroendocrine neoplasms: case report and narrative review.

PURPOSE: Pituitary metastases (PM) are uncommon findings and are mainly derived from breast and lung cancers. No extensive review of PM from neuroendocrine neoplasms (NENs) is on record. Here we describe a clinical case of PM from pancreatic NEN and review the clinical features of PM from NENs reported in the literature. METHODS: A case of PM from a pancreatic NEN followed at our institution is described. We also reviewed the 43 cases of PM from NENs reported in the literature. RESULTS: A 59-year old female patient, previously submitted to duodeno-cephalo-pancreasectomy for a well-differentiated pancreatic NEN, with known hepatic metastases, underwent a 68 Ga-DOTATOC PET/CT that revealed an uptake in the pituitary gland. A subsequent MRI displayed a pituitary lesion, with suprasellar extension. After a hormonal and genetic diagnostic workup that excluded the diagnosis of MEN 1, the worsening of headache and visual impairment and the growth of the lesion lead to its surgical removal. A pituitary localization of the pancreatic NEN was identified. Regarding the published cases of PM from NENs, the most common tumour type was small cell lung cancer (SCLC), accounting for nearly half of the cases, followed by bronchial and pancreatic well differentiated NENs. The most frequent symptom was a variable degree of visual impairment, while headache was reported in half of the cases. Partial or total anterior hypopituitarism was present in approximately three quarters of the cases, while diabetes insipidus was less common. The most frequent treatment for PM was surgical resection, followed by radiotherapy and chemotherapy. The clinical outcome was in line with previous reports of PM from solid tumours, with a median survival of 14 months. Surgery of PM was associated with prolonged survival. CONCLUSIONS: PM from NENs have clinical features similar to metastases derived from other solid tumours, albeit the involvement of the anterior pituitary seems more frequent; a thorough pituitary hormonal evaluation is mandatory, after focused radiological studies, particularly if a surgical approach is considered. The optimal management of PM remains disputed and seems mainly driven by the aggressiveness of the primary tumour and the presence of symptoms. In well-differentiated NENs, particularly in the case of symptomatic PM, surgical removal may be a reasonable approach.

Long-Term Survivors after Upfront Resection for Pancreatic Ductal Adenocarcinoma: An Actual 5-Year Analysis of Disease-Specific and Post-Recurrence Survival.

BACKGROUND: Data on long-term actual survival in patients with surgically resected pancreatic ductal adenocarcinoma (PDAC) are limited. The aim of this study was to evaluate the actual 5-year disease-specific survival (DSS) and post-recurrence survival (PRS) in patients who underwent pancreatectomy for PDAC. METHODS: Data from patients who underwent upfront surgical resection for PDAC between 2009 and 2014 were analyzed. Exclusion criteria included PDAC arising in the background of an intraductal papillary mucinous neoplasm and patients undergoing neoadjuvant therapy. All alive patients had a minimum follow-up of 60 months. Independent predictors of PRS, DSS, and survival > 5 years were searched. RESULTS: Of the 176 patients included in this study, 48 (27%) were alive at 5 years, but only 20 (11%) had no recurrence. Median PRS was 12 months. In the 154 patients after disease recurrence, independent predictors of shorter PRS were total pancreatectomy, G3 tumors, early recurrence (< 12 months from surgery), and no treatment at recurrence. Median DSS was 36 months. Independent predictors of DSS were CA19-9 at diagnosis > 200 U/mL, total pancreatectomy, N + status, G3 tumors and perineural invasion. Only the absence of perineural invasion was a favorable independent predictor of survival > 5 years. CONCLUSION: More than one-quarter of patients who underwent upfront surgery for PDAC were alive after 5 years, although only 11% of the initial cohort were cancer-free. Long-term survival can also be achieved in tumors with more favorable biology in an upfront setting followed by adjuvant chemotherapy.

Impact of PD-L1 and PD-1 Expression on the Prognostic Significance of CD8+ Tumor-Infiltrating Lymphocytes in Non-Small Cell Lung Cancer.

The immune infiltrate within tumors has proved to be very powerful in the prognostic stratification of patients and much attention is also being paid towards its predictive value. In this work we therefore aimed at clarifying the significance and impact of PD-L1 and PD-1 expression on the prognostic value of CD8+ tumor infiltrating lymphocytes (TILs) in a cohort of consecutive patients with primary resected non-small cell lung cancer (NSCLC). Tissue microarrays (TMA) were built using one representative formalin fixed paraffin embedded block for every case, with 5 cores for each block. TMA sections were stained with PD-L1 (clone SP263), PD-1 (clone NAT105) and CD8 (clone SP57). Number of CD8+ cells per mm2 were automatically counted; median, 25th and 75th percentiles of CD8+ cells were used as threshold for statistical clinical outcome analysis and evaluated in patients subgroups defined by expression of PD-L1 and PD-1 within tumors. We found an overall strong prognostic value of CD8+ cells in our cohort of 314 resected NSCLC, especially in PD-L1 negative tumors lacking PD-1+ TILs, and demonstrated that in PD-L1 positive tumors a higher density of CD8+ lymphocytes is necessary to improve the prognosis. Our data strengthen the concept of the importance of the assessment and quantification of the immune contexture in cancer and, similarly to what has been carried on in colorectal cancer, promote the efforts for the establishment of an Immunoscore for NSCLC for prognostic and possibly predictive purposes.

Recurrence after surgical resection of pancreatic cancer: the importance of postoperative complications beyond tumor biology.

BACKGROUND: Current treatment of potentially resectable pancreatic ductal adenocarcinoma (PDAC) includes pancreatic resection followed by adjuvant therapy. Aim of this study is to identify factors that are related with overall and early recurrence after pancreatectomy for PDAC. METHODS: Retrospective analysis of patients with histologically confirmed PDAC who underwent pancreatectomy between September 2009 and December 2014. Early relapse was defined as recurrence within 12 months after surgery. Univariate/multivariate analysis was performed to identify prognostic factors for recurrence. RESULTS: 261 patients were included (54% males, mean age 67 years). Neoadjuvant and adjuvant treatments were performed in 55 (21%) and 243 (93%) patients. Overall morbidity was 56% with a rate of grade 3-4 Clavien-Dindo complications of 25%. Median disease-free survival was 18 months. Multivariate analysis identified nodal metastases (OR: 3.6) and perineural invasion (OR: 2.14) as independent predictors of disease recurrence in the entire cohort. 76 patients (29%) had an early recurrence. Poorly differentiated tumors (OR: 3.019) and grade 3-4 Clavien-Dindo complications (OR: 3.05) were independent risk factors for early recurrence. CONCLUSION: Although overall recurrence is associated with tumor-related factors, severe postoperative complications represent an independent predictor of early recurrence. Patients at increased risk of severe postoperative complications may benefit from neoadjuvant therapy.

Neuroendocrine neoplasms of the duodenum, ampullary region, jejunum and ileum.

Neuroendocrine neoplasms of the small intestine are some of the most frequently occurring along the gastrointestinal tract, even though their incidence is extremely variable according to specific sites. Jejunal-ileal neuroendocrine neoplasms account for about 27% of gastrointestinal NETs making them the second most frequent NET type. The aim of this review is to classify all tumors following the WHO 2019 classification and to describe their pathologic differences and peculiarities.

Vascular resection during pancreatectomy for pancreatic head cancer: A technical issue or a prognostic sign?

BACKGROUND: There is an increased interest in venous vascular resection associated with pancreatic resection for pancreatic ductal adenocarcinoma as an upfront procedure or after neoadjuvant treatment. The aim of this study was to evaluate the impact of venous vascular resection for pancreatic ductal adenocarcinoma on postoperative and long-term outcomes. METHODS: The study is a retrospective analysis of patients who underwent pancreatectomy for pancreatic head pancreatic ductal adenocarcinoma with and without venous vascular resection between January 2010 and April 2018. The impact of venous vascular resection on postoperative and pathologic data was analyzed. Univariate and multivariate analyses of predictors of disease-free and disease-specific survival were analyzed for the entire cohort. A propensity-score matched cohort analysis was subsequently performed to remove selection bias and improve homogeneity. RESULTS: Four hundred and eighty-one patients were included, and 126 (26%) underwent a venous vascular resection. Patients undergoing venous vascular resection had higher morbidity (64% vs 54%; P = .026) with no differences in 90-day postoperative mortality (3.1 vs 2.8%; P = .5). Venous vascular resections were also significantly associated with R1 resections (52% vs 37%; P = .002) and perineural invasion (87% vs 77%; P = .017). Five-year disease-free survival in patients with and without venous vascular resection were 7% and 20% (P = .018), respectively. Independent predictors of worse disease-free survival included venous vascular resection, positive lymph node status, and perineural invasion. Independent predictors of worse disease-specific survival were perineural invasion and positive nodal status, while adjuvant treatment was a protective factor. Five-year disease-specific survival in patients with and without venous vascular resection were 19% and 35% (P = .42). CONCLUSION: Pancreatectomy with venous vascular resection can be accomplished safely. Venous vascular resections are associated with poor prognostic factors and with a worse clinical outcome, being a significant predictor of cancer recurrence.

Reliability and reproducibility among different platforms for tumour BRCA testing in ovarian cancer: a study of the Italian NGS Network.

INTRODUCTION: BRCA tumour testing is a crucial tool for personalised therapy of patients with ovarian cancer. Since different next-generation sequencing (NGS) platforms and BRCA panels are available, the NGS Italian Network proposed to assess the robustness of different technologies. METHODS: Six centres, using four different technologies, provided raw data of 284 cases, including 75 cases with pathogenic/likely pathogenic variants, for a revision blindly performed by an external bioinformatic platform. RESULTS: The third-party revision assessed that all the 284 raw data reached good quality parameters. The variant calling analysis confirmed all the 75 pathogenic/likely pathogenic variants, including challenging variants, achieving a concordance rate of 100% regardless of the panel, instrument and bioinformatic pipeline adopted. No additional variants were identified in the reanalysis of a subset of 41 cases. CONCLUSIONS: BRCA tumour testing performed with different technologies in different centres, may achieve the realibility and reproducibility required for clinical diagnostic procedures.

Angiomyolipoma of the kidney: from simple hamartoma to complex tumour.

Angiomyolipoma is the most common mesenchymal tumour of the kidney, even if for a long time it has been viewed as a hamartoma rather than a neoplasm. It belongs to a family of neoplasms, named PEComa, characterised by the constant presence of perivascular epithelioid cells that co-express smooth muscle and melanogenesis markers. Angiomyolipoma can occur in patients with tuberous sclerosis, a hereditary syndrome due to the alteration of TSC1 or TSC2 genes, or sporadically. Angiomyolipoma and its variants are indolent tumours; however, some epithelioid angiomyolipomas/pure epithelioid PEComas are aggressive, and criteria for malignancy have been proposed to identify those cases. Although typical angiomyolipoma is a straightforward diagnosis, pathologists should be aware of the wide morphological spectrum of its variants which could be tricky in routine clinical practice and could require immunohistochemical analysis for resolution. The differential diagnosis may range from an inflammatory process (for instance xanthogranulomatous pyelonephritis) to the most common renal cancers and sarcomas. The immunoexpression of melanogenesis markers (HMB45 and Melan-A) and cathepsin K is extremely helpful in the majority of cases. Recently, a subset of epithelioid angiomyolipoma/pure epithelioid PEComa harbouring TFE3 gene fusions has been described, raising questions about its relationship with the family of perivascular epithelioid cell tumour. The activation of the mTOR pathway due to genetic alterations of tuberous sclerosis complex in TSC1 or TSC2 genes in angiomyolipoma has also been reported as well as the subsequent therapeutic implications.

Inflammatory and tumor-like lesions of the pancreas.

Inflammatory/tumor-like lesions of the pancreas represent a heterogeneous group of diseases that can variably involve the pancreatic gland determining different signs and symptoms. In the category of inflammatory/tumor-like lesions of the pancreas, the most important entities are represented by chronic pancreatitis, which includes alcoholic, obstructive and hereditary pancreatitis, paraduodenal (groove) pancreatitis, autoimmune pancreatitis, lymphoepithelial cyst, pancreatic hamartoma and intrapancreatic accessory spleen. An in-depth knowledge of such diseases is essential, since they can cause severe morbidity and may represent a potential life-threatening risk for patients. Furthermore, in some cases the differential diagnosis with malignant tumors may be challenging. Herein we provide a general overview of all these categories, with the specific aim of highlighting their most important clinic-pathological hallmarks to be used in routine diagnostic activities and clinical practice.

Malignant epithelial/exocrine tumors of the pancreas.

Pancreatic malignant exocrine tumors represent the most important cause of cancer-related death for pancreatic neoplasms. The most common tumor type in this category is represented by pancreatic ductal adenocarcinoma (PDAC), an ill defined, stroma-rich, scirrhous neoplasm with glandular differentiation. Here we present the relevant characteristics of the most important PDAC variants, namely adenosquamous carcinoma, colloid carcinoma, undifferentiated carcinoma, undifferentiated carcinoma with osteoclast-like giant cells, signet ring carcinoma, medullary carcinoma and hepatoid carcinoma. The other categories of malignant exocrine tumors, characterized by fleshy, stroma-poor, circumscribed neoplasms, include acinar cell carcinoma (pure and mixed), pancreatoblastoma, and solid pseudopapillary neoplasms. The most important macroscopic, histologic, immunohistochemical and molecular hallmarks of all these tumors, highlighting their key diagnostic/pathological features are presented. Lastly, standardized indications regarding gross sampling and how to compile a formal pathology report for pancreatic malignant exocrine tumors will be provided.