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Hematological neoplasms sharing a blastic morphology may involve the skin. The skin may be either the primary site of occurrence of hematological malignancies with blastic features or cutaneous lesions are the first manifestation of an underlying systemic malignancy. The assessment of skin biopsies of hematological neoplasms with blastic features poses diagnostic problems and requires expert hematopathologists considering a wide range of differential diagnoses. The precise diagnosis of diseases sharing blastic features but with different outcomes and requiring distinct therapies is essential for patient management. The present paper mainly focuses on cutaneous involvement of the blastoid variant of mantle cell lymphoma and lymphoblastic lymphoma of B-cell or T-cell origin. The relevant literature has been reviewed and the clinical aspects, pathological features, prognosis, and therapy of both blastoid mantle cell lymphoma and lymphoblastic lymphoma involving the skin are discussed. A focus on other hematological entities with blastic features, which may involve the skin, to be taken into consideration in differential diagnosis is also given.

Mast cell leukemia (MCL) is the leukemic form of SM with at least 20% mostly immature mast cells on bone marrow aspirate. MCL may develop de novo, in the absence of a prior SM, or it may represent a progression from a previous SM. MCL may be sub-divided into the more frequent, aggressive acute form with signs of organ damage (C-findings) and the chronic form lacking C-findings and presenting a more stable course, although over time, progression to acute MCL is common. The 2022 WHO subtype of MCL with an associated hematological neoplasm was renamed MCL with an associated myeloid neoplasm in the 2022 International Consensus Classification (ICC). The relevance of the distinction between the leukemic and aleukemic forms based on the percentage of circulating mast cells is a matter of debate. The current knowledge on MCL is restricted mainly to single reports or case series with a limited number of larger studies. Our aim is to provide a comprehensive overview of this rare disease in terms of clinical manifestations, morphology, phenotype, molecular characteristics, differential diagnosis, outcome and treatment. A general overview on mastocytosis is also included.

Intravascular lymphoma is a form of lymphoid malignancy characterized by neoplastic cells growing almost exclusively within the lumina of small- to medium-sized blood vessels. Most cases are of B-cell origin with rare cases of natural killer or T-cell lineage. Extranodal sites are affected, mainly the skin and central nervous system, although any organ may be involved. Intravascular NK/T-cell lymphoma deserves special attention because of its clinicopathologic features and the need for adequate immunophenotyping combined with clonality test for a proper diagnosis. Moreover, intravascular NK/T-cell lymphoma is strongly linked to Epstein-Barr virus (EBV), which is considered to play a role in tumorigenesis and to be responsible for the aggressive behavior of the disease. In this paper, we review the current knowledge on this rare lymphoma and, in particular, the most recent advances about its molecular landscape. The main distinguishing features with other EBV-related entities, such as extranodal NK/T-cell lymphoma, EBV-positive primary nodal T/NK-cell lymphoma, and aggressive NK-cell leukemia, are discussed to help pathologists obtain the correct diagnosis and consequently develop an adequate and prompt therapy response.

The recurrent genetic anomalies used to classify prostate cancer (PC) into distinct molecular subtypes have limited relevance for clinical practice. In consideration of WHO 2016 histological classification, which includes the introduction of Gleason Score 4 for patients with cribriform component and the definition of intraductal carcinoma as a new entity, a retrospective pilot study was conducted to investigate, by histological review, if there were any variations of Gleason Score and the incidence of intraductal carcinoma and cribriform pattern, intended as "phenotypic" markers of potentially lethal PC, among metastatic castration-sensitive PC (mCSPC) and metastatic castration-resistant PC (mCRPC) samples. Potentially predictive factors were also assessed. Among 125 cases, a variation in the Gleason Score was reported in 26% of cases. A cribriform (36%) or intraductal (2%) pattern was reported in a higher percentage. Of them, a primary Gleason pattern 4 was reported in 80% of cases. All patients with intraductal carcinoma present a BRCA2 mutation, also found in 80% of cases with a cribriform pattern. This pilot study documented some hypothesis-generating data, as the evaluation of de novo mCSPC and mCRPC as phenotypic/biologic model to be translated in clinical practice. A cribriform pattern/intraductal carcinoma might be a marker of potentially lethal PC. The high incidence of TP53 and BRCA2 mutations in de novo mCSPC may also have a therapeutic implication.

Background: Para-aortic lymph node (PALN) metastases represent patterns of initial recurrence in only 2-6% CRC patients, after an estimated 23-28 month time interval. An increasing trend towards curative surgery has been witnessed in patients presenting with controlled PALN recurrence. Nevertheless, lack of consensus has impaired an unambiguous statement for PALN recurrence resection., Methods: We performed a systematic literature review following the Preferred Reporting Items for Systematic Reviews and Meta-Analyzes (PRISMA) guidelines, which led us to gain deeper insight into the prognostic factors and long-term outcomes after resection for synchronous or metachronous pathologically confirmed CRC isolated para-aortic lymph node metastases (PALNM). Pubmed/MEDLINE, Embase, Scopus, Cochrane Library and Web of Science databases were used to search all related literature., Results: The nine articles included covered a study period of 30 years (1988-2018), with a total of 161 patients. At presentation, most primary CRCs were located in the colon (74%) and 95.6%, 87.1% and 76.9% patients had T3-T4, N1-N2 and well/moderately differentiated CRC, respectively. We identified a 59.4-68% 3-year OS rate and 53.4-87.5% 5-year OS rate, with a 25-84 months median OS, 26.3-61% 3-year DFS rate and 0-60.5% 5-year DFS rate, with a 14-24 month median DFS. Overall, 62.1% re-recurrence rate ranged from 43.8% to 100%., Conclusions: Although PALNMs resection in CRC patients may be considered a feasible and beneficial option, no conclusions or recommendations can be made taking into account the current evidence. Therefore, further randomized, possibly multicenter trials are strongly recommended and mandatory if we want to have our results confirmed and patient selection criteria clearly identified.

EBV is the first known oncogenic virus involved in the development of several tumors. The majority of the global population are infected with the virus early in life and the virus persists throughout life, in a latent stage, and usually within B lymphocytes. Despite the worldwide diffusion of EBV infection, EBV-associated diseases develop in only in a small subset of individuals often when conditions of immunosuppression disrupt the balance between the infection and host immune system. EBV-driven lymphoid proliferations are either of B-cell or T/NK-cell origin, and range from disorders with an indolent behavior to aggressive lymphomas. In this review, which is divided in three parts, we provide an update of EBV-associated lymphoid disorders developing in the gastrointestinal tract, often representing a challenging diagnostic and therapeutic issue. Our aim is to provide a practical diagnostic approach to clinicians and pathologists who face this complex spectrum of disorders in their daily practice. In this part of the review, the chronic active EBV infection of T-cell and NK-cell type, its systemic form; extranodal NK/T-cell lymphoma, nasal type and post-transplant lymphoproliferative disorders are discussed.

EBV is the most common persistent virus in humans. The interaction of EBV with B lymphocytes, which are considered the virus reservoir, is at the base of the life-long latent infection. Under circumstances of immunosuppression, the balance between virus and host immune system is altered and hence, EBV-associated lymphoid proliferations may originate. These disorders encompass several entities, ranging from self-limited diseases with indolent behavior to aggressive lymphomas. The virus may infect not only B-cells, but even T- and NK-cells. The occurrence of different types of lymphoid disorders depends on both the type of infected cells and the state of host immunity. EBV-driven lymphoproliferative lesions can rarely occur in the gastrointestinal tract and may be missed even by expert pathologists due to both the uncommon site of presentation and the frequent overlapping morphology and immunophenotypic features shared by different entities. The aim of this review is to provide a comprehensive overview of the current knowledge of EBV-associated lymphoproliferative disorders, arising within the gastrointestinal tract. The review is divided in three parts. In this part, the available data on EBV biology, EBV-positive mucocutaneous ulcer, EBV-positive diffuse large B-cell lymphoma, not otherwise specified and classic Hodgkin lymphoma are discussed.

Epstein-Barr virus (EBV) is a common pathogen infecting people primarily early in life. The virus has the ability to persist throughout a person's life, usually in B lymphocytes. Conditions of immunodeficiency as well as the introduction of immunosuppressive therapies and the advent of transplant technologies has brought immunodeficiency-associated lymphoproliferative disorders into view, which are often driven by EBV. The group of EBV-associated lymphoproliferative disorders includes different entities, with distinct biological features, ranging from indolent disorders, which may even spontaneously regress, to aggressive lymphomas requiring prompt and adequate treatment. These disorders are often diagnostically challenging due to their overlapping morphology and immunophenotype. Both nodal and extra-nodal sites, including the gastrointestinal tract, may be involved. This review, divided in three parts, summarizes the clinical, pathological, molecular features and treatment strategies of EBV-related lymphoproliferative disorders occurring in the gastrointestinal tract and critically analyzes the major issues in the differential diagnosis. In this part of the review, we discuss plasmablastic lymphoma, extra-cavitary primary effusion lymphoma and Burkitt lymphoma.

Mastocytosis represents a heterogeneous group of neoplastic mast cell disorders. The basic classification into a skin-limited disease and a systemic form with multi-organ involvement remains valid. Systemic mastocytosis is a disease often hard to diagnose, characterized by different symptoms originating from either the release of mast cell mediators or organ damage due to mast cell infiltration. Gastrointestinal symptoms represent one of the major causes of morbidity, being present in 60-80% of patients. A high index of suspicion by clinicians and pathologists is required to reach the diagnosis. Gastrointestinal mastocytosis can be a challenging diagnosis, as symptoms simulate other more common gastrointestinal diseases. The endoscopic appearance is generally unremarkable or nonspecific and gastrointestinal mast cell infiltration can be focal and subtle, requiring an adequate sampling with multiple biopsies by the endoscopists. Special stains, such as CD117, tryptase, and CD25, should be performed in order not to miss the gastrointestinal mast cell infiltrate. A proper patient's workup requires a multidisciplinary approach including gastroenterologists, endoscopists, hematologists, oncologists, and pathologists. The aim of this review is to analyze the clinicopathological features of gastrointestinal involvement in systemic mastocytosis, focusing on the relevance of a multidisciplinary approach.

Background: Rarely, T-lymphoblastic lymphoma (T-LBL) may develop in the setting of myeloid/lymphoid neoplasms with eosinophilia (M/LNs-Eo), a group of diseases with gene fusion resulting in overexpression of an aberrant tyrosine kinase or cytokine receptor. The correct identification of this category has relevant therapeutic implications. LIM domain only 2 (LMO2) is overexpressed in most T-LBL, but not in immature TdT-positive T-cells in the thymus and in indolent T-lymphoblastic proliferations (iT-LBP)., Methods and Results: We retrospectively evaluated 11 cases of T-LBL occurring in the context of M/LNs-Eo. Clinical, histological, immunohistochemical and molecular features were collected and LMO2 immunohistochemical staining was performed. The critical re-evaluation of these cases confirmed the diagnosis of T-LBL with morphological, immunohistochemical and molecular features consistent with T-LBL occurring in M/LNs-Eo. Interestingly, LMO2 immunohistochemical analysis was negative in 9/11 cases, whereas only 2 cases revealed a partial LMO2 expression with a moderate and low degree of intensity, respectively., Conclusions: LMO2 may represent a potentially useful marker to identify T-LBL developing in the context of M/LNs-Eo. In this setting, T-LBL shows LMO2 immunohistochemical profile overlapping with cortical thymocytes and iT-LBP, possibly reflecting different molecular patterns involved in the pathogenesis of T-LBL arising in the setting of M/LNs-Eo.

iTLPD-GI is a low-grade clonal T-cell lymphoproliferative disease arising in GI organs. It is an uncommon disease, and only recently has it been enlisted as a distinct provisional entity in the current WHO Classification. Data from the literature disclose high heterogeneity in terms of pathological and molecular features; on the other hand, establishing an accurate diagnosis of iTLPD-GI is of pivotal importance, since treatment options are different from that of other, more frequent lymphomas that arise in the gastrointestinal tract. In this review, we aimed to better define this novel entity, and to identify useful diagnostic biomarkers; moreover, we provide a biomarker-based approach to the diagnosis and describe the most common issues in differentiating iTLPD-GI from other neoplastic and non-neoplastic disorders.

NPM1 -mutated ( NPM1 mut) acute myeloid leukemia (AML) comprises about 30% of newly diagnosed AML in adults. Despite notable advances in the treatment of this frequent AML subtype, about 50% of NPM1 mut AML patients treated with conventional treatment die due to disease progression. CD123 has been identified as potential target for immunotherapy in AML, and several anti-CD123 therapeutic approaches have been developed for AML resistant to conventional therapies. As this antigen has been previously reported to be expressed by NPM1 mut cells, we performed a deep flow cytometry analysis of CD123 expression in a large cohort of NPM1 mut and wild-type samples, examining the whole blastic population, as well as CD34 + CD38 - leukemic cells. We demonstrate that CD123 is highly expressed on NPM1 mut cells, with particularly high expression levels showed by CD34 + CD38 - leukemic cells. Additionally, CD123 expression was further enhanced by FLT3 mutations, which frequently co-occur with NPM1 mutations. Our results identify NPM1 -mutated and particularly NPM1/FLT3 double-mutated AML as disease subsets that may benefit from anti-CD123 targeted therapies.

Primary pulmonary B-cell lymphomas (PP-BCLs) comprise a group of extranodal non-Hodgkin lymphomas of B-cell origin, which primarily affect the lung without evidence of extrapulmonary disease at the time of diagnosis and up to 3 months afterwards. Primary lymphoid proliferations of the lung are most often of B-cell lineage, and include three major entities with different clinical, morphological, and molecular features: primary pulmonary marginal zone lymphoma of mucosa-associated lymphoid tissue (PP-MZL, or MALT lymphoma), primary pulmonary diffuse large B cell lymphoma (PP-DLBCL), and lymphomatoid granulomatosis (LYG). Less common entities include primary effusion B-cell lymphoma (PEL) and intravascular large B cell lymphoma (IVLBCL). A proper workup requires a multidisciplinary approach, including radiologists, pneumologists, thoracic surgeons, pathologists, hemato-oncologists, and radiation oncologists, in order to achieve a correct diagnosis and risk assessment. Aim of this review is to analyze and outline the clinical and pathological features of the most frequent PP-BCLs, and to critically analyze the major issues in their diagnosis and management.

Preoperative radiotherapy is a widely accepted treatment procedure in rectal cancer. Radiation-induced changes in the tumor are well described, whereas less attention has been given to the non-neoplastic mucosa. Our aim is to provide a detailed analysis of the morphological features present in non-neoplastic mucosa that pathologists need to be familiar with, in order to avoid misdiagnosis, when evaluating rectal cancer specimens of patients preoperatively treated with radiotherapy, especially with short-course regimen. We compared 2 groups of 95 rectal cancer patients treated preoperatively with either short-course (45 patients) or long-course radiotherapy (50 patients). Depending on the type of protocol, different histopathological features, in terms of inflammation, glandular abnormalities and endocrine differentiation were seen in the non-neoplastic mucosa within the irradiated volume. Of note, features mimicking dysplasia, such as crypt distortion, nuclear and cytoplasmic atypia of glandular epithelium, were identified only in the short-course group. DNA mutation analysis, using a panel of 56 genes frequently mutated in cancer, and p53 immunostaining were performed on both tumor and radiation-damaged mucosa in a subset of short course cases. Somatic mutations were identified only in tumors, supporting the concept that tissues with radiation-induced "dysplastic-like" features are not genetically transformed. Pathologists should be aware of the characteristic morphological changes induced by radiation. The presence of features simulating dysplasia in the group treated with short-course radiotherapy may lead to serious diagnostic mistakes, if erroneously interpreted. Next generation sequencing (NGS) analysis further validated the morphological concept that radiation-induced abnormalities do not represent pre-neoplastic lesions.