Epidemiology and geographic clustering of Erdheim-Chester disease in Italy and France.

This geoepidemiological study, performed in Italy and France, shows that Erdheim-Chester disease is increasingly diagnosed and cases cluster in specific geographic areas, namely southern Italy and central France. Disease frequency inversely correlates with the Human Development Index.

Unifocal Type-3 Mixed Histiocytosis in a 10-Years Old Child.

BACKGROUND: Histiocytoses patients present with highly heterogeneous clinical and histopathological pictures requiring multidisciplinary management. Mixed histiocytosis is a recently described group of syndromes defined by the histological overlap of Langerhans cell histiocytosis and other histiocytic proliferations that include three clinically and prognostically different conditions (i.e., Type-1-3 mixed histiocytosis). CASE REPORT: We describe a 10 year-old boy with unifocal (type-3) mixed histiocytosis - Langerhans cell histiocytosis combined with a lesion with features intermediate between Rosai-Dorfman disease and reticulohistiocytosis. Sixty months after excision, the child is disease free. DISCUSSION: Cutaneous type-3 mixed histiocytosis (Langerhans cell histiocytosis with Rosai-Dorfman disease/reticulohistiocytosis) may occur in older childhood, be unifocal, and be cured by surgical excision.

Intralymphatic Histiocytosis Associated With Tubo-ovarian High-grade Serous Carcinoma: Case Report and Review of the Literature.

Intralymphatic histiocytosis is a condition characterized by the accumulation of mononuclear phagocytes within lymphatic vessels and lymph nodes that may be isolated or secondary to autoimmune or neoplastic diseases. Secondary intralymphatic histiocytosis frequently involves the skin and is associated with malignancies in up to a tenth of cases. We describe a case of intralymphatic histiocytosis associated with high-grade serous carcinoma and reviewed the literature on neoplasia associated with the broader category of histiocytoses with raisinoid nuclei. Moreover, we try to elucidate the pathogenesis of these rare and intriguing disorders.

Indeterminate cell histiocytosis: A systematic review of the literature with a comprehensive revision of clinical, histopathological, and molecular features.

Indeterminate cell histiocytosis (ICH) is a very rare histiocytic disorder, primarily involving the skin. It affects more frequently adults, often presenting with a generalized papular eruption, and needs to be differentiated from other neoplastic, paraneoplastic, and infectious diseases through clinical and histological examination. The knowledge on ICH is limited to case reports and small series. Thus, the lack of larger multicentric studies has prevented recognizing and addressing the specific clinical need of the entity. In this systematic review, we comprehensively analysed the medical literature describing histologically-confirmed cases of ICH and divided the patients into epidemiologically and clinically different groups. We demonstrate that ICH in adulthood is strongly associated with the development of haematological (and especially myeloid) neoplasms. In this subset of patients, we identify blastic morphology of neoplastic cells as a novel independent prognostic factor and an early histopathological predictor of an associated myeloid neoplasm. Moreover, we highlight that even though ICH may also present in childhood, these patients often show indolent behaviour. Genetically, ICH emerges as a heterogeneous condition. While patients with associated myeloid neoplasms are enriched in pERK pathway gene mutations, in others a specific ETV3::NCOA2 rearrangement is described. We finally reviewe the nosology of ICH since its first description, its possible cell of origin, and summarize the therapeutic options reported for each different clinical subgroup. With this work, we hope to foster studies on rare cutaneous histiocytosis and their comprehensive multidisciplinary characterization.

Bilateral Ovarian Malakoplakia: Case Report and Review of the Literature With Clinical and Diagnostic Considerations.

Malakoplakia is a rare condition in which histiocytic cells accumulate within different organs and tissues, sometimes mimicking neoplasia. Gynecologic involvement is extremely rare and therefore may cause relevant diagnostic confusion for both clinicians and pathologists. In this paper, we described the seventh case of ovarian malakoplakia, and we reviewed the literature to compare it with the previously reported ones. Moreover, we investigated the histologic and molecular differential diagnosis of malakoplakia, with special attention to other histiocytic disorders of gynecologic interest. Finally, we discussed the most relevant points with regard to possible pathogenesis and management. Malakoplakia often represents a forgotten entity that should be remembered preoperatively, when approaching a possible gynecologic neoplasia. Moreover, it is of remarkable importance to differentiate malakoplakia from multisystem histiocytosis involving gynecologic organs. All this would prevent misdiagnosis and overtreatment of such a rare but benign condition.

MAP2K1-driven mixed Langerhans cell histiocytosis, Rosai-Dorfman-Destombes disease and Erdheim-Chester disease, clonally related to acute myeloid leukemia.

Mixed histiocytoses are a rare and recently recognized subset of histiocytic disorders that may involve the skin, characterized by the synchronous or metachronous development of lesions with Langerhans and/or non-Langerhans cell histiocytosis histopathological features. Around 10% of patients diagnosed with histiocytosis may develop a hematological malignancy, often with dramatic prognostic consequences. We hereby describe the exceptional case of a patient developing a MAP2K1-driven mixed histiocytosis with Langerhans cell histiocytosis, Rosai-Dorfman-Destombes disease, and Erdheim-Chester disease features and cutaneous involvement, progressing to a fatal and clonally-related acute myeloid leukemia. We reviewed the literature on similar cases and discussed the histopathological difficulties in their diagnosis and their clinical-pathological features.

Cutaneous-group histiocytoses associated with myeloid malignancies: A systematic review of 102 cases.

BACKGROUND: Histiocytoses are haematological disorders of bone marrow origin that share many biological and clinical features with haematological neoplasms. The association between histiocytoses of the cutaneous-group and myeloid malignancies is a poorly investigated topic of high biological and clinical impact. METHODS: We performed a systematic review of the scientific literature, compliant with PRISMA guidelines, to unravel the clinical and pathological features of this intriguing association. FINDINGS: We gathered and analysed 102 patients. Most were children with generalised cutaneous eruptions and displayed risk organ involvement (i.e. bone marrow, spleen, liver). Interestingly, all these features are uncommonly encountered in C-group histiocytosis not associated with haematological neoplasms. CONCLUSIONS: Our review shows that generalised eruptions and risk organ involvement in cutaneous-group histiocytosis should raise a suspicion for a concomitant myeloid neoplasm both in children and in adults and warrant further investigations. A rapid recognition of this association is required to start a prompt and effective therapeutic management given the aggressive behaviour of the associated myeloid neoplasm in most instances.

Targeted next-generation sequencing reveals molecular heterogeneity in non-chronic lymphocytic leukemia clonal B-cell lymphocytosis.

Non-chronic lymphocytic leukemia (non-CLL) clonal B-cell lymphocytosis (CBL) encompasses a heterogeneous group of hematologic disorders that are still poorly understood. To shed light on their biological aspects, we retrospectively analyzed a highly selected series of 28 patients, who had a clonal B-cell population in the peripheral blood and in the bone marrow, without evidence of lymphoma. Extended targeted next-generation sequencing revealed wide molecular heterogeneity with MYD88 (14%), PDE4DIP (14%), BIRC3 (11%), CCND3 (11%), NOTCH1 (11%), and TNFAIP3 (11%) as the most mutated genes. Mutations of MYD88 were "nonclassic" in most cases. Although some genetic lesions were overlapping with indolent lymphomas, mainly splenic B-cell lymphomas of marginal zone origin and splenic diffuse red pulp small B-cell lymphoma, the genetic profile of our non-CLL CBL series seemed to suggest that various pathways could be involved in the pathogenesis of these disorders, not mirroring any specific lymphoma entity. These data better enlighten the molecular characteristics of non-CLL CBL; however, more efforts are needed in order to improve the diagnostic process, prognostication, and clinical management.

The myeloproliferative neoplasms, unclassifiable: clinical and pathological considerations.

This corrects the article DOI: 10.1038/modpathol.2016.182.

The myeloproliferative neoplasms, unclassifiable: clinical and pathological considerations.

In this study, we investigate in detail the morphological, clinical and molecular features of 71 consecutive patients with a diagnosis of myeloproliferative neoplasms, unclassifiable. We performed a meticulous morphological analysis and found that most of the cases displayed a hypercellular bone marrow (70%) with normal erythropoiesis without left-shifting (59%), increased granulopoiesis with left-shifting (73%) and increased megakaryocytes with loose clustering (96%). Megakaryocytes displayed frequent giant forms with hyperlobulated or bulbous nuclei and/or other maturation defects. Interestingly, more than half of the cases displayed severe bone marrow fibrosis (59%). Median values of hemoglobin level and white blood cells count were all within the normal range; in contrast, median platelets count and lactate dehydrogenase were increased. Little less than half of the patients (44%) showed splenomegaly. JAK2V617F mutation was detected in 72% of all patients. Among the JAK2-negative cases, MPLW515L mutation was found in 17% and CALR mutations in 67% of the investigated cases, respectively. Finally, by multiple correspondence analysis of the morphological profiles, we found that all but four of the cases could be grouped in three morphological clusters with some features similar to those of the classic BCR-ABL1-negative myeloproliferative neoplasms. Analysis of the clinical parameters in these three clusters revealed discrepancies with the morphological profile in about 55% of the patients. In conclusion, we found that the category of myeloproliferative neoplasm, unclassifiable is heterogeneous but identification of different subgroups is possible and should be recommended for a better management of these patients.

Prognostic significance of a comprehensive histological evaluation of reticulin fibrosis, collagen deposition and osteosclerosis in primary myelofibrosis patients.

AIMS: To evaluate whether a comprehensive histological evaluation of reticulin fibrosis, collagen deposition and osteosclerosis in bone marrow trephine biopsies (BMBs) of primary myelofibrosis (PMF) patients may have prognostic implications. METHODS AND RESULTS: Reticulin fibrosis, collagen deposition and osteosclerosis were graded from 0 to 3 in a series of 122 baseline BMBs. Then, we assigned to each case a comprehensive score [reticulin, collagen, osteosclerosis (RCO) score, ranging from 0 to 9] that allowed us to distinguish two groups of patients, with low-grade (RCO score 0-4) and high-grade (RCO score 5-9) stromal changes. Of 122 patients, 88 displayed a low-grade and 34 a high-grade RCO score. The latter was associated more frequently with anaemia, thrombocytopenia, peripheral blood blasts and increased lactate dehydrogenase levels. The RCO score was correlated strictly with overall mortality (P = 0.013) and International Prognostic Scoring System (IPSS) risk categories, and was able to discriminate the overall survival of both low- and high-grade patients (log-rank test: P < 0.001). Moreover, it proved to be more accurate than the European Consensus on Grading of Bone Marrow Fibrosis (ECGMF grade) in identifying high-risk patients with poor prognosis. Finally, a combined analysis of RCO scores and IPSS risk categories in an integrated clinical-pathological evaluation was able to increase the positive predictive value (PPV) for mortality in high-risk patients. CONCLUSION: The comprehensive RCO score, obtained by histological evaluation of reticulin fibrosis, collagen deposition and osteosclerosis was prognostically significant and more accurate than ECGMF grade in identifying high-risk patients and improved PPV when applied in addition to IPSS.

Clonal reticulohistiocytosis of the skin and bone marrow associated with systemic mastocytosis and acute myeloid leukaemia.

AIMS: The aims of this study were to define whether diffuse cutaneous reticulohistiocytosis could be underpinned by somatic genetic alterations and represent a precursor of more aggressive forms of disease. METHODS AND RESULTS: A 59-year-old man with diffuse cutaneous reticulohistiocytosis experienced bone marrow localization of the disease, with associated systemic mastocytosis and acute myeloid leukaemia. Cytogenetic analyses of the bone marrow aspirate revealed the presence of a derivative chromosome giving rise to a partial trisomy of chromosome 1q and a partial monosomy of chromosome 9q. Therefore, we characterized the cutaneous lesions before and after chemotherapy by using an integrative approach combining histopathology, electron microscopy, and fluorescence in-situ hybridization. Histologically, the skin lesions belonged to the spectrum of diffuse cutaneous reticulohistiocytoses, as confirmed by immunohistochemistry and ultrastructural analyses. Fluorescence in-situ hybridization in the skin nodules confirmed the presence of the genetic alterations previously detected in the bone marrow. CONCLUSIONS: Here, we provide circumstantial evidence to suggest that at least a subset of cutaneous reticulohistiocytoses harbour clonal molecular alterations. Furthermore, we confirm that these lesions have the potential to arise in the setting of concurrent haematological disorders. In this hypothesis-generating study, two possible tumorigenesis models are proposed.

Whole-exome sequencing is feasible on a fresh-frozen skin sample of intravascular large B cell lymphoma.

Intravascular large B-cell lymphoma (IVLBCL) is a rare aggressive extranodal non-Hodgkin lymphoma. The predominant, if not exclusive, growth of neoplastic cells within the lumina of small-sized vessels represents the hallmark of the disease. Diagnosis is challenging due to the absence of marked lymphadenopathy, the highly heterogeneous clinical presentation, and the rarity of the condition. Clinical presentation is characterized by variable combinations of nonspecific signs and symptoms (such as fever and weight loss), organ-specific focal manifestations due to altered perfusion, and hemophagocytic syndrome. The rarity of this entity and the paucity of neoplastic cells in biopsy samples hamper the study of recurrent molecular abnormalities. The purpose of this study was to explore the feasibility of a different approach to recover a sufficient amount of DNA of acceptable quality to perform next-generation sequencing studies. Here, we report the findings of whole-exome next-generation sequencing performed on a fresh-frozen cutaneous sample of IVLBCL, paired with the patient saliva used as germline DNA. To increase the cancer cell fraction, only the subcutaneous tissue was selected. With this approach, we obtained high-quality DNA and were able to identify oncogenic mutations specific for this entity and recapitulating its post-germinal center origin, even if the tumor fraction was low. Molecular studies performed on fresh-frozen cutaneous sample are feasible in IVLBCL, especially when analysis is restricted to the subcutaneous tissue. Wide adoption of this reproducible and cost-effective approach may foster further studies, which may be of help in supporting diagnosis, providing pathogenetic insights, and guiding treatment decisions.

Cutaneous involvement in Ph-negative myeloproliferative neoplasms: from extramedullary hematopoiesis to myeloid metastasis with histiocytic differentiation. A systematic review of the literature.

Myeloid neoplasms may metastasize to the skin, presenting a wide range of clinical-pathological features that often lead to a reduction in patients' survival. The presentation varies depending on the category of myeloid neoplasm and its prognostic significance. The literature has specifically focused on the features of acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), and chronic myelomonocytic leukemia (CMML). In this article, we aimed to uncover the peculiarities of clonal skin proliferations in the course of Ph-negative myeloproliferative neoplasms (MPNs). We conducted a systematic review and statistical analysis of the literature data. MPN patients mainly exhibited cutaneous extramedullary hematopoiesis, while a minority displayed cutaneous histiocytic lesions. Furthermore, these patients showed lower survival rates compared to the median survival of MPN patients, especially when calculating survival from the appearance of cutaneous lesions. Our work highlights, for the first time, the prognostic relevance and histological heterogeneity of cutaneous lesions in MPN. Moreover, it emphasizes the importance of dermatological and histological examinations when cutaneous lesions are present.

CSF3R-mutant chronic myelomonocytic leukemia is a distinct clinically subset with abysmal prognosis: a case report and systematic review of the literature.

Chronic myelomonocytic leukemia (CMML) is a myelodysplastic syndrome/myeloproliferative neoplasm (MDS/MPN) chacaterized by persistent peripheral blood monocytosis, hypercellular bone marrow and dysplasia at least in one myeloid lineage. CMML shares much of its molecular landscape with other myeloid neoplasms, while differs from others such as chronic neutrophilic leukemia (CNL), given the high frequency of CSF3R mutations in the latter. In this article, we report a case of CSF3R-mutated CMML and dissect this rare entity by reviewing the medical literature, with the intent to understand how this rare mutation shapes CMML's clinical and morphological phenotype. CSF3R-mutated CMML emerges as a rare entity meeting the ICC/WHO diagnostic criteria for CMML and simultaneously showing clinical-pathological and molecular traits of CNL and atypical chronic myeloid leukemia, rising an important and difficult diagnostic and therapeutical issue.

Primary Large B-Cell Lymphoma of Immune-Privileged Sites of the Cerebellum: A Case Series and Review of the Literature.

Primary large B-cell lymphoma of immune-privileged sites (IP-LBCL) is a rare malignant hematological neoplasm. Involvement of the cerebellum is even rarer and its diagnosis is often difficult to make due to its non-specific clinical and radiological presentation. METHODS: We reported 3 cases of cerebellar IP-LBCL followed at our hospital and reviewed the medical literature to unravel the peculiarities of this poorly studied entity. OUTCOMES: Analyzing our cases and reviewing the literature, we could collect and study 26 cases of cerebellar IP-LBCL. To the best of our knowledge, this is the largest cohort of such patients currently published. CONCLUSION: Cerebellar IP-LBCL presents more often in adult females with cerebellum-related focal neurological signs such as ataxia, headache, and nausea. Histological confirmation is mandatory for a correct diagnosis and treatment and all cases feature diffuse large B-cell lymphoma histopathology. Compared to other encephalic IP-LBCL, cerebellar cases seem to include a higher number of cases with germinal center B-cell phenotype and better survival. These differences may be related to a different immune microenvironment and especially immunoregulation that distinguishes the cerebellum from other areas of the CNS.

Arginase-1+ bone marrow myeloid cells are reduced in myeloproliferative neoplasms and correlate with clinical phenotype, fibrosis, and molecular driver.

INTRODUCTION: Philadelphia-negative myeloproliferative neoplasms (MPN) are clonal myeloid proliferative disorders characterized by sustained systemic inflammation. Despite its renowned importance, the knowledge concerning the inflammatory pathophysiology of these conditions is currently limited to studies on serum cytokines, while cellular immunity has rarely been investigated. METHODS: In the present study, we targeted Arginase-1 immunosuppressive myeloid cells in the bone marrow of MPN patients and healthy controls and investigated their clinical and prognostic significance. We demonstrated that MPN are characterized by a significant reduction of bone marrow immunosuppressive cells and that the number of these cells significantly correlates with several clinical and histopathological features of diagnostic and prognostic importance. Moreover, we identified an unreported correlation between a reduction of Arginase-1+ bone marrow cells and the presence of CALR mutations, linking tumor-promoting immunity and molecular drivers. Finally, we postulate that the reduction of bone marrow Arginase-1+ immunosuppressive cells may be due to the migration of these cells to the spleen, where they may exert systemic immunomodulatory function. CONCLUSION: Altogether, this study preliminary investigated the contribution of cellular immunity in the pathogenesis of myeloproliferative neoplasms and identified a possible interesting therapeutic target as well as a set of new links that may contribute to unraveling the biological mechanisms behind these interesting hematological neoplasms.