Search

Crystal-storing histiocytosis is a rare entity due to tumorous deposits of histiocytes containing crystalline inclusions, which in a majority of cases are made of immunoglobulins associated with lymphoproliferative disorders, although association with non-neoplastic disorders has also been reported. The histiocytes may be so abundant to obscure the underlying lymphoplasmacytic neoplasm. On the other hand, the Gaucher-like histiocytes might lead to a misinterpretation of granulomatous inflammation or storage disease. Herein, this case study reported clinical, pathological and next generation sequencing (NGS) features of a case of kappa chain myeloma with Gaucher-like crystal-storing histiocytosis in the bone marrow (BM). The methodology included BM aspiration and biopsy, immunohistochemistry, electron microscopy and NGS study by TruSight Oncology 500. Morphologically, the BM smear showed dense infiltration of sea blue histiocytes and atypical plasma cells with rhomboid crystals in cytoplasm. The BM biopsy showed excessive plasmacytic aggregates and dense histiocytic infiltrates with wrinkled paper-like or needle shaped cytoplasm. These plasma cells were positive for CD138 and showed lambda chain restriction. Electron microscopy highlighted the long rhomboid crystals with distinct periodicity consistent with crystalline immunoglobulins in the histiocytes. In addition, the NGS study from the BM aspiration specimen revealed PARP1, MSH6, KDR, CCND3 and STK11 mutations, which might be associated with inferior survival of myeloma patients. Accordingly, this case died of pneumonia with septic shock during treatment. Our findings suggest that the presence of rhomboid crystals in bone marrow smears may alert pathologists to look for the possibility of crystal-storing histiocytosis and the prognosis of patients with multiple myeloma may depend on the genetic features of tumor cells rather than the association with crystal-storing histiocytosis., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier GmbH. All rights reserved.)

Background/aims: Ocular manifestations of histiocytosis and their genetic underpinnings are poorly characterised. This study characterises ocular sites of histiocytosis, notate genetic alterations and correlates to histiocytosis clinical features including subtype and sites of disease., Methods: Prospective registry-based study of predominantly adult histiocytosis patients at a single-institution tertiary referral centre. 180 eyes of 90 patients (46 males, 44 females) with histiocytosis (Erdheim-Chester disease 34, Rosai-Dorfman 20, xanthogranuloma 7, mixed histiocytosis 13, Langerhans cell histiocytosis (LCH) 15, ALK-positive histiocytosis 1). Ocular findings were categorised by the structure involved. Histiocytosis subtype, sites of disease and genetic status were correlated to ocular findings., Results: Ocular disease was present in more than half the histiocytosis patient cohort and occurred with other disease sites. Ocular findings were statistically significantly different across histiocytic subtypes with LCH subtypes having the lowest proportion of ocular findings (7%) and all other subtypes having rates of ocular findings which were five times that of patients with LCH (p=0.0009). Of patients with ocular findings, 41% of patients reported ocular symptoms and were significantly more in the group with ocular disease present versus those patients without ocular involvement. The presence of ocular findings was not statistically different by BRAF V600E, MAP2K1 or RAS isoform mutational status., Conclusions: Ocular disease is a common feature of histiocytosis with significant visual symptomatology and occurrence in tandem with multisystem sites. Ocular findings vary by histiocytic subtype. The mutational profile of the cohort reflects known mutations in this clinical population, with no specific driver mutation associated with ocular disease., Competing Interests: Competing interests: JHF-none, ASR-none, JC-none, RKR-consulting fees from Incyte, Celgene/MS, Blueprint, AbbVie, Promedior, CTI, Stemline, Galecto, Pharmaessentia, Protagonist, Constellation/Morphosys, Novartis, Sierra Oncology/GSK and Servier Research funding from Constellation Pharmaceuticals, Incyte, Zentalis and Stemline Therapeutics, DHA-none, ELD-unpaid editorial support from Pfizer and serves on an advisory board for Day One Biotherapeutics, Springworks Therapeutics and Opna Bio, all outside the submitted work., (© Author(s) (or their employer(s)) 2024. No commercial re-use. See rights and permissions. Published by BMJ.)

Anaplastic lymphoma kinase-positive histiocytosis, first reported in 2008, is a rare, novel type of neoplasm. To date, no more than 100 cases of anaplastic lymphoma kinase-positive histiocytosis have been reported. In this retrospective study, 12 cases of anaplastic lymphoma kinase-positive histiocytosis, including clinical symptoms, histological features, molecular pathology, treatment, and prognosis, in children were analyzed to gain a deeper understanding of the disease. All patients were Asian children, aged 2 months to 8 years and 2 months (mean 3.1 years), and the male-to-female ratio was 5:7. All patients were followed up closely. One patient died during the follow-up period, seven (case 1-7) had focal anaplastic lymphoma kinase-positive histiocytosis, and five (case 8-12) had multisystem anaplastic lymphoma kinase-positive histiocytosis. In addition, we report the case of a patient who benefited from anaplastic lymphoma kinase-targeted therapy and a patient with the rare EML4-ALK fusion gene. The current study is expected to substantially contribute to increasing the awareness of anaplastic lymphoma kinase-positive histiocytosis., Competing Interests: Declaration of competing interest All the authors have no conflicts of interest., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Histiocytoses are rare diseases characterised by infiltration of affected organs by myeloid cells with a monocyte or dendritic cell phenotype. Symptoms can range from self-resolving localised forms to multisystemic lesions requiring specific treatment. To demonstrate extremely rare cases of CD68-negative cardiac histiocytosis with expression of SARS-CoV-2 antigen in infiltrate cells. We demonstrated a case of Erdheim-Chester disease in a 67-year-old man with pericardial involvement and positive dynamics with vemurafenib treatment, an autopsy case of xanthogranulomatous myopericarditis in a 63-year-old man, surgical material of xanthogranulomatous constrictive pericarditis in a 57-year-old man, and an autopsy case of xanthogranulomatosis in a 1-month-old girl. In all cases, xanthogranuloma cells expressed CD163, many of them spike protein SARS-CoV-2, while CD68 expression was detected only in single cells. In this article, we demonstrated four cases of extremely rare CD68-negative cardiac xanthogranulomatosis in three adults and one child with expression of the spike protein SARS-CoV-2 in M2 macrophages. This potential indirect association between COVID-19 and the development of histiocytosis in these patients warrants further investigation. To substantiate this hypothesis, more extensive research is needed.

Background: Crystalloid storage histiocytosis (CSH) is a rare clinical condition characterized by abnormally high numbers of histiocytes with a large accumulation of crystalline immunoglobulins. Due to its relative rarity, clinical diagnosis of it is frequently incomplete or incorrect. We report a case with pulmonary crystal-storing histiocytosis that was mistakenly identified as lung carcinoma., Methods: Percutaneous lung biopsy, bronchoscopy., Results: Percutaneous lung biopsy pathology shows granulomatous inflammation with massive eosinophilic infiltration, immunohistochemistry shows CD68, kappa positive, S-100, desmin, myogenin, lambda negative. The final diagnosis is pulmonary crystal-storing histiocytosis., Conclusions: To get pathology tissue for a definitive diagnosis, patients with pulmonary nodules who have changes in tumor markers or nodule size should have bronchoscopy or percutaneous lung biopsy done as soon as possible.

SLC29A3 spectrum disorder, also known as histiocytosis-lymphadenopathy plus syndrome (HLPS), presents a wide variety of multi-systemic manifestations that can be mistaken for other conditions. Herein, we report a 9-year-old girl who presented with a complex clinical presentation since birth, including chronic generalized lymphadenopathy in association with hepatosplenomegaly, short stature, flexion contractures, hearing loss, hyperpigmentation, and heart anomalies. She was ultimately diagnosed with the SLC29A3 spectrum disorder., (© 2024 Wiley Periodicals LLC.)

Aims/Background Indeterminate cell histiocytosis is a rare proliferative histiocytic disease with an unknown aetiology, which shares immunophenotypic features of both Langerhans cells and macrophages. There is a relationship between indeterminate cell histiocytosis and cancer, while there are no reports about indeterminate cell histiocytosis and bullous pemphigoid. In this study, we reported the rare case of a patient with primary cutaneous indeterminate cell histiocytosis who had been diagnosed with oesophagal cancer and later developed bullous pemphigoid. The objective of this clinical case report is to analyse the association between solid tumours and indeterminate cell histiocytosis and focus on the coexistence of indeterminate cell histiocytosis and bullous pemphigoid in a patient with cancer. Case Presentation This study presented the case of a 75-year-old man who exhibited annular erythema lesions of variable size and papules scattered over his chest, abdomen, and limbs, along with four bullae on his thigh, persisting for 1.5 months. The patient also had a 9-month history of oesophageal cancer treated with radical radiotherapy. Histopathology and immunohistochemistry confirmed cutaneous indeterminate cell histiocytosis. Bullae and blisters developed on the lower limbs 38 days after treatment. A diagnosis of bullous pemphigoid was established based on clinical and histopathological features and results of direct immunofluorescence and enzyme-linked immunosorbent assay. Results Histopathological examination of the abdominal lesion revealed an accumulation of mononuclear cells in the dermis, with infiltration of eosinophils and lymphocytes in the superficial dermal layer. The histology of the blister on the thigh indicated the formation of an old subepidermal blister, with slurry and eosinophils present within the blister, and infiltration of eosinophils, lymphocytes, as well as histiocytoid cells in the superficial dermal layer. Immunohistochemical staining was positive for CD1a, S100, and CD68, and negative for CD207. Histopathological examination of blisters and bullae on the lower limbs revealed a subepidermal blister with infiltration of a large number of eosinophils within the blister and the dermis beneath it. Direct immunofluorescence showed that immunoglobulin Gs (IgGs) were linearly deposited in the basal membrane zone. Conclusion The coexistence of oesophageal carcinoma, indeterminate cell histiocytosis, and bullous pemphigoid in a single patient represents a rare case that warrants consideration of possible underlying mechanisms.

Background: The SLC29A3 gene, which encodes a nucleoside transporter protein, is primarily located in intracellular membranes. The mutations in this gene can give rise to various clinical manifestations, including H syndrome, dysosteosclerosis, Faisalabad histiocytosis, and pigmented hypertrichosis with insulin-dependent diabetes. The aim of this study is to present two Iranian patients with H syndrome and to describe a novel start-loss mutation in SLC29A3 gene., Methods: In this study, we employed whole-exome sequencing (WES) as a method to identify genetic variations that contribute to the development of H syndrome in a 16-year-old girl and her 8-year-old brother. These siblings were part of an Iranian family with consanguineous parents. To confirmed the pathogenicity of the identified variant, we utilized in-silico tools and cross-referenced various databases to confirm its novelty. Additionally, we conducted a co-segregation study and verified the presence of the variant in the parents of the affected patients through Sanger sequencing., Results: In our study, we identified a novel start-loss mutation (c.2T > A, p.Met1Lys) in the SLC29A3 gene, which was found in both of two patients. Co-segregation analysis using Sanger sequencing confirmed that this variant was inherited from the parents. To evaluate the potential pathogenicity and novelty of this mutation, we consulted various databases. Additionally, we employed bioinformatics tools to predict the three-dimensional structure of the mutant SLC29A3 protein. These analyses were conducted with the aim of providing valuable insights into the functional implications of the identified mutation on the structure and function of the SLC29A3 protein., Conclusion: Our study contributes to the expanding body of evidence supporting the association between mutations in the SLC29A3 gene and H syndrome. The molecular analysis of diseases related to SLC29A3 is crucial in understanding the range of variability and raising awareness of H syndrome, with the ultimate goal of facilitating early diagnosis and appropriate treatment. The discovery of this novel biallelic variant in the probands further underscores the significance of utilizing genetic testing approaches, such as WES, as dependable diagnostic tools for individuals with this particular condition., (© 2024. The Author(s).)

H syndrome is a rare autosomal recessive genodermatosis that falls under the histiocytosis-lymphadenopathy plus syndrome. The term "H syndrome" includes manifestations such as hyperpigmentation, hypertrichosis, hepatosplenomegaly, heart anomalies, hearing loss, hypogonadism, low height, and occasionally hyperglycemia. The syndrome is associated with mutations in the SLC29A3 gene, which encodes the human equilibrative transporter 3 present in endosomes, lysosomes, and mitochondria. The generalized and ubiquitous presence of affected lysosomes and mitochondria contributes to the systemic and phenotypically heterogeneous manifestations of the syndrome. H syndrome manifestations are cutaneous, systemic, and organ-specific. The pathognomonic signs are hypertrichosis and hyperpigmentation in the inner thighs and shins. However, not all patients present with these symptoms. H syndrome management involves a multidisciplinary approach to address specific symptoms and complications. The prognosis of H syndrome depends on several factors, including the extent and severity of clinical manifestations, the presence of complications, and timely diagnosis and management. Further studies are needed to explore the association between prognosis and the different mutations encountered in H syndrome., (Copyright © 2024 Hematology/Oncology and Stem Cell Therapy.)

Crystal-storing histiocytosis (CSH) is a rare condition in which crystals accumulate in the cytoplasm of histiocytes and is usually associated with a lymphoplasmacytic neoplasm. Cutaneous CSH is extraordinarily rare and limited to case reports in the literature. We report two cases of this disease with cutaneous involvement. Case 1 was a 65-year-old male with a 4-month history of a pruritic eruption that started as a solitary pink to skin-colored indurated plaque on the anterior neck before progressing to involve the whole neck, chest wall, and face. Case 2 was a 54-year-old woman with a history of unspecified "lymphoma" who presented with a soft nodule on the forearm. Biopsies from both cases had similar findings and showed a proliferation of epithelioid cells with pink cytoplasm and intracellular crystalline structures infiltrating the dermis and subcutaneous fat. In the first case, the cells were positive for CD43, CD45, CD68, and IgG kappa, and in the second case, the crystals were positive for IgG lambda. Based on these findings, the patients were diagnosed with cutaneous CSH. We highlight this rare diagnosis and the importance of investigating an underlying lymphoplasmacytic neoplasm., (© 2024 The Authors. Journal of Cutaneous Pathology published by John Wiley & Sons Ltd.)

Objectives: Histiocytic disorders are pathologic expansions of myeloid cells in multiple organs, including the CNS. They share activation of the MAP kinase pathway due to either BRAF V600E variant or other variants in the RAS-RAF-MEK-ERK pathway. The rarity and heterogeneity of the disease only enable therapy through pathophysiologic considerations., Methods: We present 2 histiocytosis cases without BRAF sequence variants that affect the CNS, one with Erdheim-Chester disease and the other with an unspecified histiocytosis, and their diagnostic and therapeutic challenges., Results: In both cases, comprehensive analysis of the RAS-RAF-MEK-ERK signaling pathway secured the diagnosis. Treatment with the MEK inhibitor cobimetinib brought the disease to a complete halt. However, side effects such as thrombosis and serous macular edema made it necessary to reduce cobimetinib dosage. Low-dose cobimetinib maintenance medication was successful in preventing recurrence of histiocytic disease., Discussion: CNS involvement of histiocytic disorders can lead to detrimental neurologic symptoms. MEK inhibitors are effective treatment options for some of these patients. Since side effects are common, according to our cases we propose a low-dose treatment of 20 mg per day to balance treatment effects with side effects., Classification of Evidence: This case report provides Class IV evidence. This is a single observational study without controls.

Background: Histiocytoses are rare disorders characterized by the accumulation of macrophages, dendritic cells, or monocyte-derived cells in various tissues and organs of children and adults, with a wide range of clinical manifestations, presentations, and histology. The histiocytoses are classified according to the WHO Classification, the last version of which was published in 2022, or according to the Histiocyte Society Classification, with the last version published in 2016., Purpose: This text provides an overview of histiocytoses as described in the WHO Classification 2022.

Hereditary progressive mucinous histiocytosis (HPMH) is an extremely rare progressive non-Langerhans cell histiocytic disorder presenting with only cutaneous manifestations. Patients typically present with multiple asymptomatic dome-shaped erythematous papules, usually involving the face and upper extremities. Twenty-six cases have been reported worldwide, with no spontaneous regression. Treatment with thalidomide stopped the progression of the disease in two cases. We report a case of progressive mucinous histiocytosis in a 31-year-old female patient with a history of tuberculosis who presented papular lesions on the face that later extended to the hands. She was treated with isoniazid for tuberculosis and isotretinoin for the skin lesions; the improvement was minimal during the next two months, with new lesions appearing on both hands. Thalidomide stopped the progression of the disease. The cause and pathogenesis of HPMH are undetermined. The pathogenesis of HPMH may be similar to that of lysosomal storage disease, considering the intra-cytoplasmic phospholipid deposition in both diseases, in addition to the likelihood of a role of macrophages in triggering the disease. In our patient, tuberculosis may have contributed.

Background: Crystal-storing histiocytosis (CSH), light chain proximal tubulopathy (LCPT), and light chain crystalline podocytopathy (LCCP) are rare complications of multiple myeloma (MM) or monoclonal gammopathy of renal significance, and their diagnoses are challenging., Case Presentation: In this case, a 69-year-old Chinese woman presented with suspicious Fanconi syndrome with renal insufficiency. Immunofixation electrophoresis of both serum and urine revealed elevated immunoglobulin G kappa (IgGkappa) and kappa light chain. Bone marrow aspirate revealed 15% plasma cells with considerable cytoplasmic granular inclusions and needle-shaped crystals. Renal biopsy confirmed the final pathologic diagnosis of kappa-restricted CSH, combined LCPT and LCCP by immunoelectron microscopy. A number of special casts were present which could easily be misdiagnosed as light chain cast nephropathy. Immunofluorescence on frozen tissue presented false negative for kappa light chain, as ultimately proven by paraffin-embedded tissue after pronase digestion. MM and CSH were diagnosed, and two cycles of chemotherapy were given. The patient subsequently refused further chemotherapy, and her renal function remained relatively stable during a 2.5-year follow-up period., Conclusions: In conclusion, we report a rare case of generalized kappa-restricted CSH involving bone marrow and kidney, combined with LCPT and LCCP, provide a comprehensive summary of renal CSH, and propose a new nomenclature of monoclonal immunoglobulin-induced crystalline nephrology. The presentation of monoclonal immunoglobulin and Fanconi syndrome should suggest the presence of monoclonal immunoglobulin-induced crystalline nephrology. Use of paraffin-embedded tissue after pronase digestion and immunoelectron microscopy is beneficial to improve the sensitivity of diagnosis.

Background: Crystal-storing histiocytosis (CSH) is a rare disorder which most commonly occurs in the setting of concurrent lymphoproliferative disease. Morphologically, it consists of aggregates of histiocytes containing eosinophilic crystalline material, which in most cases is composed of aggregated abnormal light chains., Methods: Using histomorphology, immunohistochemistry and in situ hybridization, the authors characterize a rare case of orbital CSH associated with extranodal marginal zone (MALT) lymphoma and report for the first time the frozen section features of CSH., Results: The frozen section featured plump histiocytes with ample weakly basophilic to grayish cytoplasm with a microvacuolated appearance and focal stippling. These features stand in contrast with the formalin-fixed, paraffin embedded histomorphological appearance of aggregates of plump histiocytes with densely eosinophilic crystalline cytoplasmic material., Conclusion: CSH is a challenging diagnosis to make on frozen section. The artifacts that preclude its recognition, as well as differential diagnoses of this entity in the head and neck are discussed., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Histiocytoses are inflammatory myeloid neoplasms often driven by somatic activating mutations in mitogen-activated protein kinase (MAPK) cascade genes. H syndrome is an inflammatory genetic disorder caused by germ line loss-of-function mutations in SLC29A3, encoding the lysosomal equilibrative nucleoside transporter 3 (ENT3). Patients with H syndrome are predisposed to develop histiocytosis, yet the mechanism is unclear. Here, through phenotypic, molecular, and functional analysis of primary cells from a cohort of patients with H syndrome, we reveal the molecular pathway leading to histiocytosis and inflammation in this genetic disorder. We show that loss of function of ENT3 activates nucleoside-sensing toll-like receptors (TLR) and downstream MAPK signaling, inducing cytokine secretion and inflammation. Importantly, MEK inhibitor therapy led to resolution of histiocytosis and inflammation in a patient with H syndrome. These results demonstrate a yet-unrecognized link between a defect in a lysosomal transporter and pathological activation of MAPK signaling, establishing a novel pathway leading to histiocytosis and inflammation., (© 2023 by The American Society of Hematology.)

Aims: The aim was to test the expression of PU.1 on different types of histiocytoses and to test the utility of PU.1 in confirming or excluding a histiocytic origin in tumour samples with suspicion of histiocytosis., Methods and Results: We analysed 66 biopsies of nonmalignant histiocytoses represented by Langerhans-cell histiocytosis (n = 13), Erdheim-Chester disease (ECD) (n = 19), Rosai-Dorfman disease (RDD) (n = 14), mixed ECD-RDD (n = 3), ALK-positive histiocytosis (n = 6), and juvenile xanthogranuloma (n = 11). All cases were positive for PU.1 in reactive and neoplastic histiocytes. In addition, 39 cases of tumours with high-grade cytological atypia were referred to our center as suspicion of malignant histiocytosis/histiocytic sarcoma and only 18 were confirmed. Indeed, more than half of these tumours (21/39) were either undifferentiated malignant tumours with a stroma rich in histiocytes, diffuse large B-cell lymphoma, or high-grade dedifferentiated liposarcoma. PU.1 was useful to distinguish between the negativity of large atypical nuclei and the positivity of stromal reactive histiocytes., Conclusion: PU.1 is expressed by all types of histiocytosis. It distinguishes histiocytosis from histiocyte-rich tumours with an easy interpretation due to its sharp nuclear staining. Its negativity in lesional/tumour cells in histiocyte-like lesions is useful to eliminate a histiocytosis., (© 2023 The Authors. Histopathology published by John Wiley & Sons Ltd.)

A 45-year-old female patient was found to have a nodule in the right lower lobe on physical examination. Chest CT showed the nodule was lobulated measuring 24 mm×23 mm, with obvious enhancement and adjacent pleural traction. As the PET-CT showed increased 18 F-FDG uptake suggesting malignancy, the wedge resection of the right lower lobe was performed. Grossly, the mass was adjacent to the pleural area with indistinct boundary. On cut sections, the lesion was solid and tough, with a greyish-pink colour. Microscopically, the lesion had an ill-defined margin, and was composed of spindle and polygonoid histiocytes with rich eosinophilic cytoplasm similar to rhabdoid muscle cells. The cytoplasm of histiocytes was filled with diamond-shaped or club-shaped crystals. Immunohistochemistry (IHC) showed the histiocytes were positive for CD68, κ, λ, IgG, IgM and IgA. The patient had been followed up for 41 months and had shown neither recurrences nor new diseases. CSH is a rare non-neoplastic histiocytic proliferative disease. Pulmonary CSH should be differentiated from multiple diseases. Accurate pathological diagnosis depends on its morphology and immunophenotype. This disease is often related to potential lymphoproliferative or plasma cell disorder. After diagnosis, a systemic examination is required and long-term follow-up is recommended.

Crystal-storing histiocytosis (CSH) is a rare disease associated with the accumulation of histiocytes containing crystalline matter within their cytoplasm. Herein, we present the case of a female patient who was diagnosed with Tolosa-Hunt syndrome at 45 years of age and idiopathic retroperitoneal fibrosis when she was 48 years. She developed portal hypertension (PH), but did not present with cirrhosis; as such, the cause of PH was not identified. Her PH gradually worsened when she was 54 years, and at the age of 60 years, she died from an acute subdural hematoma. Autopsy revealed retroperitoneal fibrosis with severe fibrosis extending around the hepatic veins and into the porta hepatis. Histologically, the retroperitoneal tissue showed a dense infiltrate of eosinophilic histiocytes with crystal structures in the cytoplasm, which was pathologically diagnosed as CSH. Nodular regenerative hyperplasia was observed in the liver parenchyma, whereas cirrhosis was not. In the present case, CSH caused fibrosis, which was believed to be the cause of PH. In addition, we considered that nodular regenerative hyperplasia caused by the altered hepatic blood flow due to treatment of gastric varices contributed to worsening PH. Hence, CSH should be considered as an underlying disease in noncirrhotic portal hypertension., (© 2023. Japanese Society of Gastroenterology.)

Background: Anaplastic lymphoma kinase (ALK)-positive histiocytosis, a novel rare histiocytic proliferation, was first described in 2008; it occurs in early infancy with liver and hematopoietic involvement. The spectrum was subsequently broadened to include localized diseases in older children and young adults. However, its full clinicopathological features and molecular lineage have not been fully elucidated., Results: Here, we report four cases of multisystem ALK-positive histiocytosis without hematopoietic involvement. Clinically, three patients were adults aged between 32 and 51 years. Two patients', whose main manifestations were intracranial mass and numerous micronodules in the thoracoabdominal cavity organs and skin papules respectively, had a partial response to ALK inhibitors after surgery. One patient presented with mediastinal neoplasm without surgical treatment, and progressive disease occurred after two years of ALK inhibitor therapy. The fourth patient was a 17-month-old male with a large intracranial mass and presented with a poor response to ALK inhibitor and chemoradiotherapy; he died eight months after surgery. Pathologically, the histiocytes were large, with abundant eosinophilic cytoplasm, and mixed with variable numbers of foamy cells and Touton giant cells. Interstitial fibrosis was also observed. Histiocytes were positive for macrophage markers (CD68 and CD163) and ALK. KIF5B-ALK fusions were detected in two cases, EML4-ALK in one, and both DCTN1-ALK and VRK2-ALK fusions were detected in one case., Conclusions: We observed that ALK inhibitors present robust and durable responses in adult patients but a poor response in young children with central nervous system involvement. There is no consensus on the optimal treatment regimen and long-term prognosis requires further observation. Moreover, every unusual histiocytic proliferative lesion, especially unresectable and multisystem involvement, should be routinely tested for ALK immunohistochemical staining to identify this rare disease., (© 2023. The Author(s).)

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., Competing Interests: The authors declare no conflict of interest., (Copyright © 2022 by the International Society of Gynecological Pathologists.)

Histiocytes and dendritic cells may display cytological atypia and an aberrant immunophenotype even in reactive processes. Herein, we describe two cases of "Hodgkinoid histiocytosis" that show distinctive clinicopathological features, mimicking morphologically classic Hodgkin lymphoma (CHL), but suggesting reactive histiocytic/dendritic cell proliferation in lymph nodes. Both the patients presented with peripheral lymphadenopathy and blood eosinophilia with skin manifestations. Lymph node biopsy revealed scattered large histiocytes resembling Hodgkin cells with a round or stellate shape, abundant cytoplasm, and distinct nucleoli admixed in a predominant inflammatory background. The Hodgkinoid histiocytes occasionally showed emperipolesis. They expressed CD30, S100, and PD-L1 proteins but lacked PAX5 and CD1a expressions, Epstein-Barr association, BRAF V600E mutation, and PD-L1 gene amplification. Neither of the patients showed overt progression to malignant haematopoietic neoplasms during the disease course. An identical case series of four patients has been reported to date. Both these series highlight the potential of being interpreted as CHL due to the presence of Hodgkinoid histiocytes with CD30 positivity., (© 2022 John Wiley & Sons Ltd.)

Abstract: Indeterminant cell histiocytosis (ICH) is a rare lymphoproliferative disorder that demonstrates features of Langerhans and non-Langerhans cell histiocytoses and diagnosis can be challenging. We present a case of a 62 year old woman with a generalized eruption of erythematous papules on the face, trunk and extremities. Skin biopsies demonstrated a dermal mononuclear cell infiltrate with monocytic (CD4, CD33), histiocytic (CD68, CD163), and dendritic cell (CD1a) immunophenotype but negative for Langerhans' cell marker (CD207). The differential diagnosis included leukemia cutis and ICH, and further workup revealed a normal bone marrow biopsy. To confirm the diagnosis of ICH, next generation sequencing with ETV3-NCOA2 gene fusion was performed and was positive. The patient's condition improved with methotrexate and narrow band UVB phototherapy. Our case adds to the existing literature supporting the use of next-generation sequencing to test for ETV3-NCOA2 gene fusion in suspected cases of ICH., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Background: Among the histiocytic disorders, anaplastic lymphoma kinase (ALK)-positive histiocytosis emerged in 2008. As more and more cases of the novel entity are reported, our understanding of it is deepened. However, only a few cases with central nervous system (CNS) involvement have been reported. Furthermore, the lesion in the suprasellar region has not been documented.  CASE PRESENTATION: We presented a case of ALK-positive histiocytosis involving the suprasellar region of a one-year-and-four-month-old boy. Through clinical, neuropathological, and genomic analyses, the patient was diagnosed with ALK-positive histiocytosis. After lesions were resected he started treatment with a combination of the three compounds vincristine, prednisolone, and crizotinib, but they did not work. Cytarabine was then added as an additional chemotherapy drug for him, and the lesions in the brain and lungs were shrunk by combining treatment of crizotinib, dexamethasone, vincristine, and cytarabine according to the RECIST (esponse Evaluation Criteria In Solid Tumours)., Conclusions: Additional adjuvant chemotherapy drugs are needed when ALK-inhibitor treatment is ineffective., (© 2022. The Author(s).)

Purpose: To describe and illustrate recent reclassification and clinical descriptions of the histiocytoses, diagnosis and management, and effects on the eye and adnexae., Patients and Methods: Literature review with an illustrative case series of seven patients with histiocytosis and ophthalmic involvement from a single tertiary centre., Results: Skin lesions with signs including eyelid mass, orbital bone destruction, bizarre keratic precipitates, limbal or iris mass, haemorrhagic anterior uveitis, subretinal lesions of uncertain etiology, ischaemic retinopathy, optic neuropathy, and apparent steroid-resistant inflammations should be comprehensively investigated., Conclusions: Ophthalmic involvement in histiocytosis is rare. Clinical manifestations vary from limited single-organ disease to lethal systemic infiltration or malignancy. Radiology may identify lesions for biopsy. Histology with appropriate markers is essential. Oncology advice may be required.

Histiocytic proliferations are heterogeneous lesions with distinct pathogenic and clinical-pathological features. While many of these conditions are nonspecific immune responses to variable causes, a minority of them is associated with specific etiological factors and unique clinical-pathological pictures. By presenting a rare case of Whipple adenopathy, we address the peculiar histological features of this condition and the differential diagnosis of nodal histiocytosis in general.

Rosai-Dorfman-Destombes histiocytosis is a rare histiocytosis characterized by an accumulation of histiocytes within the tissues. It is a heterogeneous entity with various clinical phenotypes: isolated lymph nodes, in association with extranodal involvement, autoimmune disease or neoplasm. These extra nodal lesions mainly affect the skin, the nasal cavity, orofacial sinuses, or are lytic bone lesions or even damage to the central nervous system. The diagnosis is histopathological. We present here the case of a histiocytosis of Rosai-Dorfman-Destombes in a 46-year-old patient with a lesion of the left palate. Our observation discuss the diagnostic hypotheses in front of a lytic lesion of the ENT sphere predominantly histiocytic., (Copyright © 2021 Elsevier Masson SAS. All rights reserved.)

Introduction: Histiocytic disorders pose significant diagnostic and management challenges for the clinicians due to diverse clinical manifestations and often non-specific histopathologic findings. Herein, we report the tumor board experience from the first-of-its-kind Histiocytosis Working Group (HWG)., Materials and Methods: The HWG was established in June 2017 and consists of experts from 10 subspecialties that discuss cases in a multidisciplinary format. We present the outcome of tumor board case discussions during the first 2 years since its inception (June 2017-June 2019)., Results: Forty cases with a suspected histiocytic disorder were reviewed at HWG during this time period. Average number of subspecialties involved in HWG case discussion was 5 (range, 2-9). Histiocytosis Working Group tumor board recommendations led to significant changes in the care of 24 (60%) patients. These included change in diagnosis (n = 11, 27%) and change in treatment (n = 13, 33%)., Conclusion: Our report highlights the feasibility of a multidisciplinary tumor board and its impact on outcomes of patients with histiocytic disorders., (© The Author(s) 2022. Published by Oxford University Press.)

Purpose: To report a rare case of crystal-storing histiocytosis associated with solitary extramedullary plasmacytoma of the lacrimal sac and to review literature on the 2 entities to summarize important diagnostic, management, and prognostic considerations., Methods: A case report of the ophthalmologic presentation, pathology workup, and oncologic management is presented. Literature search with focus on lesions occurring in ophthalmic sites and management guidelines from expert panels and working groups., Results: Crystal-storing histiocytosis associated with solitary extramedullary plasmacytoma arose within the lacrimal sac of a previously healthy middle-aged woman and presented as a painless nodule with epiphora. The biopsy tissue showed sheets of crystal-filled histiocytes, interspersed with monoclonal plasma cells and rarely demonstrated plasma cell phagocytosis. Imaging and laboratory studies confirmed the localized nature., Conclusions: Crystal-storing histiocytosis is an uncommon entity in which crystals, most commonly arising from altered immunoglobulins, aggregate within histiocytes and form symptomatic mass lesions. It has been reported in ophthalmic regions in patients with a concurrent lymphoproliferative or plasma cell disorder and can rarely predate a malignancy. The current case is notable because crystal-storing histiocytosis occurs with a localized process, solitary extramedullary plasmacytoma, and presents in an unusual site, the lacrimal sac. Tissue biopsy with multimodal pathological evaluation is necessary to make the diagnosis. Ophthalmologists should recognize that crystal-storing histiocytosis is commonly associated with a hematologic malignancy and, when appropriate, refer the patient for oncologic management. Surveillance may be indicated in cases with no established etiology. Solitary extramedullary plasmacytoma should also be monitored, as a proportion of cases progress to multiple myeloma., Competing Interests: The authors have no financial or conflicts of interest to disclose., (Copyright © 2021 The American Society of Ophthalmic Plastic and Reconstructive Surgery, Inc.)

Anaplastic lymphoma kinase (ALK)-positive histiocytosis is a rare emerging entity characterized by systemic or localized proliferation of histiocytes harboring ALK rearrangements. Breasts are reportedly affected by ALK-positive histiocytosis. Here, we evaluated 2 localized cases of breast ALK-positive histiocytosis through a comprehensive clinicopathologic, molecular, and genomic analysis to further delineate this entity and better understand its pathogenesis. The cases involved 2 undiagnosed ALK-positive spindle-cell breast lesions. Both cases were Asian women aged 30s to 40s who underwent excisions for asymptomatic breast masses. Macroscopically, both lesions were well-circumscribed, solid masses. Microscopically, both lesions were predominantly composed of fascicles with uniform, bland spindle cells, admixed with epithelioid histiocyte-like cells and lymphoid aggregates. Immunohistochemically, the spindle and epithelioid cells coexpressed ALK and histiocytic markers (eg, CD68, CD163). Genetically, both lesions harbored KIF5B-ALK, confirmed by fluorescence in situ hybridization and polymerase chain reaction-direct sequencing analyses. Combining these results, both cases were successfully diagnosed as ALK-positive histiocytosis. Furthermore, no common or previously annotated somatic alterations were identified by whole-exome sequencing. One case harbored clonal immunoglobulin gene rearrangements according to the polymerase chain reaction-based BIOMED-2 protocol. Therefore, ALK-positive histiocytosis can be accurately diagnosed through a combination of morphologic, immunohistochemical, and molecular analyses. In this entity, breast cases may have distinct clinicopathologic features: Asian women aged 30s to 40s, asymptomatic masses, and predominant spindled morphology. For pathogenesis, ALK rearrangements could be the driver alteration, and a subset of ALK-positive histiocytosis may harbor a lymphoid lineage. These findings can be utilized to improve the diagnosis of ALK-positive histiocytosis and better understand its pathogenesis., Competing Interests: Conflicts of Interest and Source of Funding: The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Abstract: Cheilitis granulomatosa (CG) is an idiopathic, rare, and chronic granulomatous disorder involving the lips. We characterized the pathological and immunohistopathological findings of these granulomas and their relationship with the lymphatic vessels. Pathologically confirmed cases of primary CG from 2001 to 2016 were collected. Cases of inflammatory cheilitis without the presence of granuloma were included in the control group. Demographic data, clinical presentation, response to therapy, and pathological differences were compared. Periodic acid-Schiff and acid-fast stains excluded patients having infections. CD68, CD163, and D2-40 stains demonstrated features of granuloma, macrophage polarization, and the relationship between granuloma and lymphatic vessels. Thirteen patients diagnosed with CG were enrolled. Thirteen people were enrolled in the control group. The granulomas were either mononuclear or sarcoidal. They were predominantly positive for CD68 but negative for CD163. Perilymphatic granulomas were found in all patients. Intralymphatic histiocytosis and lymphatic dilatation were more commonly observed in patients diagnosed with CG than those in controls (54% vs. 15%, P = 0.03 and 92% vs. 23%, P < 0.01). TH1 immune response due to CD68+ M1 macrophages results in CG. Perilymphatic aggregation of macrophages and intralymphatic histiocytosis were important pathological clues for diagnosis., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)