Cervical lymph nodes in rheumatology: A diagnostic dilemma

The case is presented on a 52-year-old male patient, who was seen in the Rheumatology department. He had painless lymph nodes in the cervical, axillary, supraclavicular, and neck region. He also had a fever, and parotid and submaxillary gland enlargement. Complementary studies were performed, showing normocytic-normochromic anemia, thrombocytopenia and eosinophilia, impaired renal function with hypoalbuminaemia and hematuria, ANA 1/5120, Sm+, ACL+. Biopsies were also performed on the compromised tissues, reaching the diagnosis of Rosai-Dorfman Disease and IgG4-related Disease. Differential diagnoses of cervical, axillary and inguinal lymph nodes, with fever, renal and hematological compromise are discussed.

Se describe el caso de un paciente varón de 52 años que consulta al servicio de reumatología por presentar adenopatías indoloras en las regiones cervical, axilar, supraclaviculares y en la nuca, así como fiebre, aumento de tamaño de parótidas y submaxilares. Se realizan estudios complementarios que arrojan como resultado anemia normocítica-normocrómica, trombocitopenia y eosinofilia, alteración de la función renal con hipoalbuminemia y hematuria, FAN 1/5.120, Sm+, ACL+ y biopsia de los tejidos comprometidos, por lo que se arriba al diagnóstico de enfermedad de Rosai-Dorfman y enfermedad relacionada con IgG4. Se discuten diagnósticos diferenciales de adenopatías cervicales, axilares e inguinales, fiebre, compromiso renal y hematológico.

Reticulohistiocitosis multicéntrica: una gran simuladora dentro de la Reumatología / Multicentric reticulohistiocytosis: a great pretender within Rheumatology

La reticulohistiocitosis multicéntrica (RHM) es una histiocitosis de células no Langerhans, multisistémica, rara, caracterizada por afectación cutánea y articular, que poco frecuentemente afecta a otros órganos. El diagnóstico se basa en hallazgos clínicos y resultados de biopsias de piel o sinovial, sin describirse un parámetro de laboratorio específico. Realizamos una revisión de la literatura en relación a las características clínicas de esta entidad desde el punto de vista reumatológico.

Multicentric reticulohistiocytosis (MHR) is a rare, multisystem, non-Langerhans cell histiocytosis characterized by skin and joint involvement, and rarely involving other organs. Diagnosis is based on clinical findings and results of skin or synovial biopsies; a specific laboratory parameter has not been described. We conducted a review of the literature regarding the clinical characteristics of this entity from a rheumatological point of view.

Enfermedad de Erdheim-Chester: primer caso pediátrico reportado en Colombia / Erdheim-Chester disease: First pediatric case report in Colombia

Resumen | La enfermedad de Erdheim-Chester es una condición extremadamente rara en la edad pediátrica. Se presenta el caso de una niña de 12 años con diagnóstico histológico y radiológico de enfermedad de Erdheim-Chester multisistémica y mutación en el gen BRAF, que requirió tratamiento con dabrafenib. Hasta el momento, se han reportado 22 casos pediátricos en el mundo y este es el segundo en Latinoamérica. Se observó el hallazgo radiológico denominado signo oscuro paraselar, descrito hasta ahora en pacientes con hipofisitis autoinmunitaria para diferenciarlos de aquellos con adenomas hipofisarios. Este reporte contribuye a la literatura médica en dos aspectos fundamentales: las manifestaciones clínicas de la enfermedad y su diagnóstico en la población pediátrica.

Abstract | The Erdheim-Chester's disease is extremely rare in children. We present the case of a 12-year-old girl with histological and radiological diagnosis of this disease and mutation of the BRAF gene, who developed multisystemic compromise requiring treatment with dabrafenib. We identified 22 reports of this condition among children worldwide and this is the second pediatric case in Latin America. Diagnostic imaging is critical to confirm Erdheim-Chester disease and for the surgical planning of the biopsy. Additionally, we identified the parasellar dark sign, which has previously been reported on lymphocytic hypophysitis. This report contributes to the current practice as it shows the clinical presentation and the diagnostic workout of this disease in pediatrics.

Histiocitosis de células de Langerhans: reporte de caso y revisión de la literatura / Langerhans cell histiocytosis: Case report and literature review

Resumen La histiocitosis de células de Langerhans comprende un grupo heterogéneo de enfermedades inflamatorias cuyos principales componentes celulares son las células dendríticas y los macrófagos. El infiltrado inflamatorio puede afectar la piel y otros órganos, y el resultado clínico varía de leve a letal, dependiendo del subconjunto de células involucradas y el compromiso multisistémico. La demora en el diagnóstico puede ocurrir debido a su presentación inespecífica y a que los médicos tratantes no suelen sospecharla. Se reporta el caso de una lactante mayor a la cual, a pesar de múltiples consultas con síntomas inespecíficos pero característicos de la enfermedad, solamente se le pudo hacer el diagnóstico gracias a los hallazgos histopatológicos.

Abstract Histiocytosis comprises a heterogeneous group of inflammatory diseases whose main cellular components are dendritic cells and macrophages. The inflammatory infiltrate can affect the skin and other organs and the clinical outcome varies from mild to fatal depending on the involved cell subset and multisystemic compromise. Delay in diagnosis may occur due to its non-specific presentation and to a low suspicion on the part of the clinician. We report the case of an infant who despite multiple consultations with nonspecific but characteristic symptoms of the disease was only finally diagnosed thanks to histopathological findings.

Síndrome hematofagocítico como manifestación inicial de linfoma de Hodgkin clásico / Hemophagocytic syndrome as the initial manifestation of Hodgkin lymphoma

Introducción: las histiocitosis son un grupo heterogéneo de enfermedades; una de ellas es el síndrome hematofagocítico (SHF). Sus causas pueden ser infecciosas, neoplásicas, autoinmunes o relacionadas a inmunodeficiencias adquiridas; el linfoma de Hodgkin clásico (LHc) es una causa poco frecuente. Se reporta el caso de un hombre inmunodeprimido de 35 años que ingresa al hospital febril y con insuficiencia respiratoria grave.Métodos: se recopiló información clínica pertinente y se revisó material de biopsia estudiado con tinción de hematoxilina ­ eosina, técnica inmunohistoquímica e hibridación in situ cromogénica. Resultados: estudios de laboratorio muestran pancitopenia, altera-ción de pruebas hepáticas, hipertrigliceridemia, hipoalbuminemia e hiperferritinemia. El estudio de médula ósea hematopoyética con mielograma y biopsia muestran hallazgos compatibles con LHc, signos de hemofagocitosis e infección por virus Epstein-Barr (VEB). Se diagnostica SHF como primera manifestación de LHc e infección por VEB. Conclusiones: a la fecha, se describen 74 pacientes re-portados con SHF como manifestación de LHc; en el 84% fue su primera manifestación. Si bien la presentación clínica presentada es infrecuente, se ha propuesto una asociación en hombres con inmunodeficiencia, SHF, LHc e infección por VEB; por lo que se sugiere una sospecha diagnóstica alta.

Introduction: histiocytosis are a heterogeneous group of diseases; one of them is the hemophagocytic syndrome (HS). Its causes can be infectious, neoplastic, autoimmune or related to acquired immunodeficiencies; classic Hodgkin lymphoma (cHL) is a rare cause.We present the case of an immunosuppressed 35-year-old male who was admitted with fever and acute respiratory failure. Methods:pertinent clinical reports and biopsy material were reviewed; including hematoxylin-eosin stained slides from formalin-fixed and pa-raffin-embedded tissue blocks and immunohistochemical and chromogenicin situhybridisation studies. Results:laboratory studies revealed pancytopenia, abnormal liver functions, hypertriglyceridemia, hypoalbuminemia e hyperferritinemia. Bone marrow aspiration smear and biopsy showed a malignant lymphoid neoplasm consistent with cHL, signs of hemophagocytosis, and Epstein-Barr virus (EBV) infection. HS, as an initial manifestation of cHL, was diagnosed.Conclusions:to our best knowledge, there are 74 reported cases of cHL with HS; in 84% it was the initial clinical manifestation. Though this is an unusual presentation, an association between immu-nodeficiency, HS, cHL, and EBV infection has been proposed; so a high diagnostic suspicion is suggested.

Traversing the spectrum of non-Langerhans Cell Histiocytosis: A case of Rosai-Dorfman Disease with features of Necrobiotic Xanthogranuloma

Introduction@#Non-Langerhans cell histiocytoses (non-LCH) are a group of rare diseases with varied clinical manifestations and overlapping features seen among the subtypes. Here, we present a case of Rosai-Dorfman disease with features of necrobiotic xanthogranuloma. @*Case@#A 45-year-old female presented with a 10-year history of an enlarging neck mass with normal overlying skin accompanied by dysphagia and multiple asymptomatic pink to yellowish-brown papules, nodules, and plaques on the face, trunk and extremities. Biopsies of a skin nodule and plaque revealed granulomatous dermal infiltrates (lymphocytes, foamy histiocytes, and Touton giant cells), emperipolesis and areas of necrosis. CD1A and Fite-Faraco staining showed negative results while CD68 and S100 positively stained the tissues of interest. Histopathology of the neck mass paralleled these findings in addition to being negative for lymphoid markers. Patient had monoclonal gammopathy and thyromegaly with enlarged cervical lymph nodes on further tests and imaging. Intralesional and systemic steroids were given which led to flattening of skin lesions and improvement in dysphagia, respectively. @*Conclusion@#Diagnosis and classification of a particular type of non-LCH may be difficult due to similarities across its subtypes. Hence, it is our belief that these diseases may occur on a spectrum. Treatment involves a multidisciplinary approach for the best possible care.

Xantogranuloma juvenil del adulto con presentación única en el conducto auditivo externo, una entidad poco común y una localización infrecuente: reporte de caso / Juvenile xanthogranuloma in an adult with a single manifestation in the external auditory canal, an uncommon entity and unusual localization: Case report

La xantogranulomatosis juvenil es una patología infrecuente que se presenta predominantemente en la primera infancia, ya que los adultos pueden verse afectados con poca frecuencia. La manifestación cutánea se da en la mayoría de los casos como un nódulo rojo-amarillo indurado y solitario, que con frecuencia se presenta a nivel de cabeza y cuello, seguido del tronco, extremidades inferiores y superiores. Aunque infrecuentes, las manifestaciones extracutáneas pueden presentarse con principal compromiso oftalmológico (1). En el artículo se presenta el caso de un hombre de 42 años que consultó por la aparición de una lesión en el conducto auditivo externo derecho, con un aumento progresivo del tamaño asociado con otorrea serohemática intermitente e hipoacusia. El diagnóstico se realizó por medio de hallazgos clínicos, histopatológicos e inmunohistoquímicos. Se realizó escisión total de la lesión; posteriormente, el paciente presentó una evolución adecuada y mejoría de la sintomatología. Se presenta este caso por lo infrecuente de la entidad y por lo inusual de su localización.

Juvenile xanthogranulomatosis, an unusual pathology that occurs predominantly in early childhood, adults can be affected infrequently, the skin manifestation occurs in most cases, as a solitary, indurated red-yellow papule or nodule, with a highest frequency occurs at head and neck level, followed by the trunk and the lower and upper extremities. Extracutaneous manifestations are uncommon, however they can be present with principal ocular level involvement (1). We present the case of a 42-year-old man who consulted due to an appearance of a lesion in the right external auditory canal with a progressive increase in size associated with intermittent otorrhea and hearing loss. The diagnosis was made by clinical, histopathological and immunohistochemical findings. Excision of the entire lesion was performed, after which the patient presented adequate evolution and improvement of symptoms. This case is presented due to the infrequency of the entity and the unusual localization

Histiocitosis congénita de células de Langerhans / Congenital Langerhans cell histiocytosis

La histiocitosis de células de Langerhans es una enfermedad poco frecuente, cuyas manifestaciones clínicas pueden aparecer en el periodo neonatal y varían desde lesiones óseas aisladas hasta un compromiso sistémico. Se describe un caso de histiocitosis de células de Langerhans y se revisa la literatura médica sobre las manifestaciones clínicas, el diagnóstico y el tratamiento. El paciente de un mes de nacido fue llevado a consulta por presentar adenopatías y lesiones en la piel que, inicialmente, fueron tratadas como reacción a una infección. La enfermedad continuó su progresión sin que hubiera mejoría con el tratamiento, hasta que el paciente falleció por falla respiratoria. La biopsia de ganglio linfático y la de piel revelaron infiltración de células atípicas, y la inmunohistoquímica resultó positiva para las proteínas S1OO, CD1 y CD68, con lo cual se confirmó el diagnóstico de histiocitosis de células de Langerhans. Esta alteración representa un gran desafío clínico, por lo que es importante alertar y sensibilizar al equipo médico para lograr un diagnóstico y un tratamiento más oportunos.

Langerhans cell histiocytosis is a rare pathology with different clinical manifestations in the neonatal period ranging from isolated bone lesions to systemic compromise. We report a case of Langerhans cell histiocytosis including a literature review focused on the clinical manifestations, diagnosis, and treatment. A one-month-old patient was brought to medical consultation with lymphadenopathy and skin lesions, which were initially managed as an infectious pathology. The disease continued its progression without improvement with the treatment until the patient died due to respiratory failure. The lymph node and skin biopsies revealed infiltration of atypical cells with positive immunohistochemistry for S1OO, CD1, and CD68 confirming Langerhans cell histiocytosis. This disorder represents a great challenge and, therefore, it is important to alert and sensitize medical teams about it for timely diagnosis and management.

Enfermedad de Erdheim-Chester: Serie de diecinueve casos y un diagnóstico diferencial de relevancia / Erdheim-Chester Disease: Series of nineteen cases and a relevant differential diagnosis

La enfermedad de Erdheim-Chester (EEC) es una histiocitosis de células no Langerhans de presentación proteiforme y escaso conocimiento. Se presenta una serie de 19 casos de 4 centros, registrados de junio de 2012 a junio de 2019. Se incluyeron aquellos pacientes con clínica, anatomía patológica e inmunohistoquímica característica de la enfermedad. Se excluyeron pacientes con hallazgos indefinidos. Resultados: al igual que en la literatura, el compromiso más frecuente fue el óseo por imagenología, la mitad de estos sintomático. Nuestra serie presenta mayor incidencia de mujeres (casi 70%). Siete pacientes presentaron nódulo mamario como forma de presentación. La mayoría recibieron dosis media de esteroides asociado a otra droga inmunosupresora. La mortalidad fue del 16%. Conclusión: comunicamos una serie de pacientes con la EEC mencionando las características más destacables. Es llamativo el número de pacientes con afectación mamaria, por lo cual proponemos téngase en cuenta en el diagnóstico diferencial de la patología tumoral mamaria.

Erdheim-Chester disease (ECD) is a non-Langerhans histiocytosis, protein manifestations at start and little known. We included 19 patients from June 2012 to June of 2019. Inclusion criteria: clinical features, histopathology and immunostaining compatible with ECD. We excluded patients with undefined features. Results: Bones were the most frequent affected, half of them were asymptomatic. Seventy per cent of the patients were women, and 7 of them developed a nodule breast as first manifestation of ECD. The patients were treated with corticosteroids associated or not with immunosuppressants. The mortality rate was 16%. Conclusion: We reported a series of patients with ECD, enhancing the most frequent features. It is striking the number of patients with breast involvement; we propose to include the Erdheim-Chester disease in differential diagnosis of breast tumor.

Intravascular histiocytosis: case report of a rare disease probably associated with silicone breast implant

Abstract Intravascular histiocytosis is a rare condition characterized by the aggregate of histiocytes within dilated dermal vessels. The diagnosis is mainly histophatological and immunohistochemical. We describe a case of a 55 year-old female patient presenting erythematous/purple patches on the breasts, back and limbs. She previously presented ductal carcinoma in the right breast in 2006 which was treated with mastectomy and proceeded to silicone breast implant in 2009. Clinical hypothesis was telangiectatic metastatic carcinoma. Histopathology showed vascular ectasia, thrombosis and recanalization of upper dermis small vessels. On immunohistochemistry, intravascular cells were CD 68+ and negative for estrogen and progesterone receptors, CK7, EMA and AE1/AE3 and endothelial cells were CD64+, leading to the diagnosis of intravascular histiocytosis.

Síndrome de Rosai-Dormfan associada a Lúpus eritematoso sistêmico: relato de caso / Rosai-Dorfman syndrome associated with systemic erythematous lupus: case report

Objetivo: Relatar um caso de associação de Síndrome de Rosai-Dorfman e Lúpus Eritematoso Sistêmico acompanhado no ambulatório de Clínica Médica de nosso Hospital Universitário. Metodologia: O estudo é em formato de relato de caso, realizado a partir de revisão de prontuário e exames complementares. O termo de consentimento livre e esclarecido foi assinado pela paciente. Resultados: Paciente do sexo feminino, 37 anos, com quadro de pneumonia associada a derrame pleural recorrente e linfonodomega-lia generalizada. Na investigação clínica, foi realizado diagnóstico de Lúpus Eritematoso Sistêmico. Os exames anatomopatológico e imuno-histoquímico da biópsia linfonodal foi compatível com Síndrome de Rosai-Dorfman. Conclusões: A Síndrome de Rosai-Dorfman é uma doença benigna que pode mimetizar neoplasias. A progressão da doença é variável e não há tratamento efetivo estabelecido atualmente, sen-do o seguimento regular importante para avaliar compressão de estruturas vitais. Lúpus eritematoso sistêmico é uma doença inflamatória crônica com acometimento multissistêmico. Seu tratamento adequado costuma resultar em sobrevida longa e com qualidade. Importância do problema e comentários: De acordo com nosso levantamento bibliográfico, este é o quarto artigo relatando a ocorrência concomitante de Síndrome de Rosai-Dorfman e Lúpus Eritematoso Sistêmico em um paciente (AU)

Objective: To report a case of association of Rosai-Dorfman syndrome and Systemic Lupus Erythema-tosus followed at the Internal Medicine ambulatory of our University Hospital. Methodology: This stu-dy is in a case report format, carried out from a review of medical records and complementary exams. The consent form was signed by the patient. Results: Female patient, 37 years old, with a history of pneumonia associated with recurrent pleural effusion and generalized lymphadenopathy. In the clini-cal investigation, Systemic Lupus Erythematosus was diagnosed. The anatomopathological and im-munohistochemical exams of lymph node biopsy were compatible with Rosai-Dorfman Syndrome. Conclusions: Rosai-Dorfman Syndrome is a benign disease that can mimic neoplasms. The disease progres-sion is variable and, currently, there is no effective treatment established. Regular follow-up is important to assess vital structures compression. Systemic Lupus Erythematosus is a chronic inflammatory disease with multisystem affection. The appropriate treatment usually results in long-term and high-quality survival. Pro-blem impact and comments: According to our bibliographic survey, this is the fourth article reporting the concomitant occurrence of Rosai-Dorfman Syndrome and Systemic Lupus Erythematosus in a patient (AU)

Crystal-Storing Histiocytosis with Plasma Cell Neoplasm in the Setting of Chronic Carbamazepine Exposure

No abstract available.

Primary Necrobiotic Xanthogranulomatous Sialadenitis with Submandibular Gland Localization without Skin Involvement

Necrobiotic xanthogranulomatous reaction is a multiorgan, non-Langerhans cell histiocytosis with an unknown etiology. Occurrence in the salivary gland is extremely rare. We recently identified a case of necrobiotic xanthogranulomatous sialadenitis in a 73-year-old Korean woman who presented with a painless palpable lesion in the chin. There was no accompanying cutaneous lesion. Partial resection and subsequent wide excision with neck dissection were performed. Pathological examination showed a severe inflammatory lesion that included foamy macrophages centrally admixed with neutrophils, eosinophils, lymphocytes, plasma cells, and scattered giant cells, as well as necrobiosis. During the 12-month postoperative period, no grossly remarkable change in size was noted. Necrobiotic xanthogranulomatous inflammation may be preceded by or combined with hematologic malignancy. Although rare, clinicians and radiologists should be aware that an adhesive necrobiotic xanthogranuloma in the salivary gland may present with a mass-like lesion. Further evaluation for hematologic disease and close follow-up are needed when a pathologic diagnosis is made.

A Stepwise Diagnostic Approach to Cystic Lung Diseases for Radiologists

Lung cysts are commonly seen on computed tomography (CT), and cystic lung diseases show a wide disease spectrum. Thus, correct diagnosis of cystic lung diseases is a challenge for radiologists. As the first diagnostic step, cysts should be distinguished from cavities, bullae, pneumatocele, emphysema, honeycombing, and cystic bronchiectasis. Second, cysts can be categorized as single/localized versus multiple/diffuse. Solitary/localized cysts include incidental cysts and congenital cystic diseases. Multiple/diffuse cysts can be further categorized according to the presence or absence of associated radiologic findings. Multiple/diffuse cysts without associated findings include lymphangioleiomyomatosis and Birt-Hogg-Dubé syndrome. Multiple/diffuse cysts may be associated with ground-glass opacity or small nodules. Multiple/diffuse cysts with nodules include Langerhans cell histiocytosis, cystic metastasis, and amyloidosis. Multiple/diffuse cysts with ground-glass opacity include pneumocystis pneumonia, desquamative interstitial pneumonia, and lymphocytic interstitial pneumonia. This stepwise radiologic diagnostic approach can be helpful in reaching a correct diagnosis for various cystic lung diseases.

A Case of Rosai-Dorfman Disease Presented with Neck Mass / 대한이비인후과학회지

Rosai-Dorfman disease, also known as the sinus histiocytosis with massive lymphadenopathy, is a rare and benign histioproliferative disease in which lymphadenopathy results from infiltration and dilatation of lymph node sinuses by large histiocytes. We experienced a case of a 59-year-old man, presenting bilateral cervical masses with pain since one month ago. Radiologically, there were multiple enlarged lymph nodes with homogenous contrast enhancement at both cervical areas. Excisional biopsy revealed that the tumor was consistent with the Rosai-Dorfman disease. The patient was treated successfully with corticosteroid. Herein, we report our experiences with literature reviews.

Langerhans Cell Histiocytosis as Cause of Central Diabetes Insipidus: Case Report

Langerhans cell histiocytosis (LCH) is a rare disease of the monocyte-macrophage system, characterized by the aberrant proliferation of specific dendritic cells. The clinical presentation ranges from a single bone lesion to widespread multiorgan involvement. This disease is usually considered to be a disease of childhood; however, the diagnosis is frequently made in adulthood. The course of the disease is fairly unpredictable and varies from spontaneous resolution to progress into a debilitating form, which compromises the vital functions with occasional fatal consequences. Langerhans cell histiocytosis exhibits a predilection for the hypothalamic-pituitary-axis, with diabetes insipidus being the most common endocrine consequence related to the disease, which may be prior to diagnosis or develop at any time during the course of the disease. The diagnosis of LCH should be based on histologic and immunophenotypic examination of a lesional biopsy, although other testing may be done, depending on the symptoms. There is no established, widely agreed-upon treatment of LCH, in general. The treatment depends upon the individual patient and the extent and areas of involvement. The present article aims to describe the case of a 26-year-old male patient whose symptoms started with a headache and occipital bone lesion that progressed later with diabetes insipidus.

A histiocitose de células de Langerhans (HCL) é uma rara doença do sistema monocítico-macrofágico, caracterizada pela proliferação aberrante de células dendríticas específicas. As manifestações clínicas variam de uma única lesão óssea a um acometimento extenso de múltiplos órgãos. Esta doença geralmente é considerada uma doença da infância; no entanto, o diagnóstico é frequentemente feito na idade adulta. O curso da doença é bastante imprevisível e varia de resolução espontânea a progressão para uma forma debilitante, com comprometimento de funções vitais e ocasionais consequências fatais. A HCL exibe uma predileção pelo eixo hipotálamohipofisário, sendo o diabetes insípido a consequência endócrina mais comum relacionada à doença, podendo ser anterior ao diagnóstico ou se desenvolver a qualquer momento durante o curso da doença. O diagnóstico de HCL deve basearse nos exames histológico e imunofenotípico de uma biópsia lesional, embora outros exames possam ser feitos a depender dos sintomas apresentados pelo paciente. Não existe um tratamento estabelecido, amplamente aceito para a HCL, em geral. O tratamento depende individualmente do paciente, da extensão e das áreas de envolvimento. O presente artigo tem como objetivo descrever o caso de um paciente do sexo masculino de 26 anos de idade que iniciou o quadro com uma cefaleia e lesão óssea occipital que evoluiu posteriormente com quadro de diabetes insípido.

Erdheim-Chester Disease Involving Lymph Nodes and Liver Clinically Mimicking Lymphoma: A Case Report

Erdheim-Chester disease (ECD) is a rare non-Langerhans cell histiocytosis and multisystem disease. First described in 1930, there are no more than 750 cases reported. The etiology remains unknown, but a majority of cases of ECD and Langerhans cell histiocytosis were found to have clonal mutations involving genes of the mitogen-activated protein kinase pathway. We recently encountered a 53-year-old male patient with extensive ECD involving the systemic lymph nodes, pleura, liver, and long bones clinically mimicking malignant lymphoma. Biopsies were performed at multiple sites, including a pleural mass, an external iliac lymph node, bone marrow, and the liver. Based on histopathological and immunohistochemical findings of positivity for CD68 and negativity for CD1a and S-100, the patient was diagnosed with ECD. Interferon-α was administered as the first-line treatment, but the patient rapidly progressed to hepatic failure after 2 months of treatment. We report this rare case of ECD clinically mimicking malignant lymphoma and diagnosed by careful pathological review.

Erdheim-Chester Disease Presenting as an Anterior Mediastinal Tumor without Skeletal Involvement

Erdheim-Chester disease (ECD) is a form of non–Langerhans cell histiocytosis that most commonly involves the skeletal system. We report an unusual case of ECD presenting as an anterior mediastinal tumor without skeletal involvement. A 60-year-old man with no remarkable medical history was referred for evaluation of a mediastinal mass. The patient underwent surgical excision of the tumor via video-assisted thoracoscopic surgery. Histologic examination revealed marked proliferation of atypical histiocytes with sclerosis, and the results of immunohistochemical staining were suggestive of ECD.