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A systematic literature review revealed 88 Rosai-Dorfman Disease (RDD) cases affecting the orbit. We present a review of the literature on orbital RDD in addition to two brothers with isolated bilateral extra-nodal orbital RDD cases associated with G-6PD deficiency. The disease manifested as asymmetric extensive orbital and paranasal sinus infiltration, with orbital bone destruction. Orbital mass debulking and steroids improved the condition in both patients. This is the most extensive case series of orbital RDD reported, including clinical manifestation, imaging, pathologic results, management, and outcome. Vigilant follow-up is essential to monitor for potential malignant transformation, systemic manifestations, potential vision loss, or life-threatening recurrences.

Rosai-Dorfman disease (RDD), also known as sinus histiocytosis with massive lymphadenopathy, is an uncommon benign disorder characterized by the accumulation of activated histiocytes in affected tissues. While RDD typically involves lymph nodes, it may manifest as extranodal involvement. Breast involvement is an exceedingly rare presentation of this condition with <100 reported cases worldwide. This report presents a case of RDD in a 58-year-old male patient who presented with a palpable breast mass. Mammography and ultrasound imaging studies raised concerns for malignancy, prompting a breast biopsy. Histopathological examination revealed S100-positive pale histiocytes exhibiting emperipolesis, consistent with RDD. The management of extranodal RDD is individualized, as no standardized guidelines are currently available. However, surgical excision is recommended for unicentric breast lesions, which was performed in our case, resulting in complete remission. The patient has remained disease-free under surveillance with computed tomography scans. Our case underscores the importance of considering RDD in the differential diagnoses of breast masses and highlights the utility of surgical excision as an effective treatment option, especially for unicentric breast lesions of RDD.

Histiocytosis is a group of rare diseases characterized by inflammation and accumulation of cells derived from monocytes and macrophages in different tissues. The symptoms are highly variable, from mild forms with involvement of a single organ to severe multisystem forms that can be life compromising. The diagnosis of histiocytosis is based on the clinic, radiological findings and pathological anatomy. A biopsy of the affected tissue is recommended in all cases as it may have therapeutic implications. During the last decade, some mutations have been identified in the affected tissue that condition activation of the MAPK/ERK and PI3K/AKT pathway, in a variable proportion depending on the type of histiocytosis. In this review we mainly focus on Langerhans Cell Histiocytosis, Erdheim-Chester Disease and Rosai-Dorfman Disease.

Melanoma and benign histiocytic proliferations can sometimes show considerable clinical and histopathologic overlap. Recently, cases of melanomas resembling xanthogranuloma and Rosai-Dorfman disease have been reported, and herein we report a case of melanoma closely mimicking reticulohistiocytoma. An 84-year-old man presented with a 1 cm purple-red nodule on his arm concerning for squamous cell carcinoma. While the biopsy findings resembled reticulohistiocytoma, the clinical context and regression changes at the lesion perimeter raised stronger concern for melanoma, which was confirmed with immunohistochemistry. We review prior rare reports of melanomas resembling non-Langerhans cell histiocytic proliferations and summarize helpful clinical and histopathologic clues to avoid a diagnostic pitfall when confronted with this unusual quandary.

Rosai-Dorfman Disease (RDD), also known as sinus histiocytosis with massive lymphadenopathy, is an uncommon histiocytic condition characterized by massive histopathological aggregation of CD1-a negative, CD68-positive, and S100-positive histiocytes. It was initially described by Destombes in 1965 under the term \"adenitis with lipid excess.\" However, it is named after Rosai and Dorfman who reported further histopathological features of the disease in 1969. The diagnosis of this non-Langerhans cell histiocytosis can be challenging and requires high clinical suspicion. The diagnostic process usually involves imaging, tissue biopsies, and genetic testing as needed. In this case series, we are presenting three cases of rare disease. Case 2 had both nodal and extranodal forms, which makes this case rarer than cases 1 and 3, which present with extranodal lesions.

Three cases of primary Rosai-Dorfman disease of the thymus and lung are presented. The patients are 3 men between the ages of 42 and 47 years who presented with non-specific symptoms including cough, chest pain, and shortness of breath. Clinically, the patients did not have any other pertinent clinical history. Diagnostic imaging revealed in one patient a cystic anterior mediastinal mass, while in two other patients the imaging was that of an intrapulmonary mass, one in the right upper lobe and the other in the left lower lobe. The three patients undergo surgical resection of the mass. In the cases in which the tumor mass was in the lung, both patients had a lobectomy while in the patient with anterior mediastinal mass, surgical resection via thoracotomy was performed. The intrapulmonary tumors were described as soft and yellowish measuring 2.5 and 3.0 cm in greatest diameter, while the mediastinal mass was described as cystic measuring 4.0 cm in diameter. Histologically, all tumors show similar features in terms of a proliferation of large histiocytes admixed with an inflammatory component composed predominantly of plasma cells. Immunohistochemical stains show positive staining for CD68 and S-100 protein, while negative for keratin, CD1a, and langerin. The cases herein presented highlight the ubiquitous distribution of Rosai-Dorfman disease and the importance of keeping this entity in the differential diagnosis of histiocytic proliferation in the thymus or lung.

Rosai-Dorfman disease (RDD), otherwise known as sinus histiocytosis with massive lymphadenopathy (SHML), is a very rare and typically benign disorder of unknown etiology with <10% bone involvement. The report is of a case seen at the authors\' hospital of a patient presenting with several months\' onset unspecified nontraumatic ankle pain. There was no physical mass or lymphadenopathy appreciated on examination. Plain radiographs and magnetic resonance images demonstrated an osteolytic lesion at the medial malleolus. Biopsy revealed the diagnosis of intraosseous manifestation of Rosai-Dorfman disease.

Non-Langerhans cell histiocytosis, including Rosai-Dorfman disease (RDD) and xanthogranuloma are rare disorders with occasional overlapping in the histopathological and immunohistochemical (IHC) findings. We report the case of a 53-year-old woman with erythematous-violaceous plaques on the cheeks and edema in the auricular pavilions. A biopsy was performed and the histopathological examination revealed a histiocytic proliferation with emperipolesis characteristic of RDD and lymphoplasmocitic infiltrate. IHC analysis showed S100 and CD68 positivity in the histiocytes but was negative for CD1a, supporting the diagnosis of RDD. Molecular analysis failed to detect BRAF-V600, NRAS or KRAS mutation. We discuss the differential diagnosis of cutaneous non-Langerhans cell histiocytosis. Pathologist must be aware of unusual presentations of RDD and further treatment options must be explored for patients with unresectable lesions and/or resistance to the classical management of RDD.

An 81-year-old man presented with anemia, fatigue, weight loss, and recurrent urinary tract infections and was found to have diffuse large adenopathy and infiltrating renal masses. Surgical excision of a lymph node and histologic evaluation led to the diagnosis of Rosai-Dorfman disease, a rare histioproliferative condition that classically presents with enlarged cervical lymph nodes bilaterally. It also can involve additional nodal chains and/or have extranodal manifestations. The condition can self-resolve or have periods of remission and reactivation.