Langerhans cell sarcoma (LCS) is a rare aggressive malignancy with a poor prognosis. Our knowledge about this condition is limited and mainly based on case reports, making it challenging to understand its epidemiology, clinical features, and patient outcomes. We conducted a retrospective study of LCS patients diagnosed between 2000 and 2019 using the Surveillance, Epidemiology, and End Results (SEER) database. The data were stratified based on age, race, stage, clinical pattern, and treatment method. Our study found that 57 LCS cases were reported in SEER registries between 2000 and 2019. Among these cases, most patients (50.9%) were over 60 years old and White (71.9%) with almost equal males to females ratio. About 45.6% of cases were localized while 47.4% were at distant stages. Of the patients, 50.9% underwent surgery, 45.6% received chemotherapy, and only 21.1% received radiotherapy. The overall survival rate for patients diagnosed with LCS in the United States is generally low with a 1-year overall rate of 63.8%. Certain factors can negatively impact prognosis, such as advanced stages of the disease, secondary tumors, or more than 1 tumor per patient. LCS is a rare disease with poor survival rates. Future research should incorporate global data for further statistically significant results. Moreover, investigating the molecular, genetic, and pathophysiological backgrounds of these tumors is crucial for developing targeted management strategies and improving prognosis.

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BACKGROUND: Langerhans cell sarcoma (LCS) is a very rare malignant tumor of Langerhans cells that may metastasize to many organs. The diagnosis of this tumor is difficult and its prognosis is poor.
OBJECTIVE: To report the difficulty to diagnose LCS, and discuss therapeutic management of this rare entity.
METHODS: We report a case of LCS in a 52-year-old man who presented with an axillar lymphadenopathy. The diagnosis of nodular sclerosis type Hodgkin\'s disease was established after histologic examination. The patient was treated with chemotherapy (ABVD regimen: Doxorubicin, Bleomycin, Vinblastine, Dacarbazine) and radiotherapy with a partial response. However, disease recurrence was observed and histological analysis confirmed the diagnosis of Langerhans cell sarcoma. A revision of the initial histological examination concluded to the diagnosis of sarcoma from the beginning. We chose the ESHAP (Etoposide, Methylprednisolone, Aracytine, Cisplatin) regimen and clinical improvement of LCS was obtained after 2 cycles but the patient had a fatal outcome and died by disease progression.
CONCLUSIONS: Because of its rarity, diagnosis is difficult and an optimal treatment strategy for this disease has not yet been identified. Polychemotherapy can be an effective modality for the treatment of LCS.

Transformation of follicular lymphoma (FL) to a Langerhans cell (LC) neoplasm is extremely uncommon. The shared IGH::BCL2 rearrangement is a robust finding in most transformed tumors underscoring that the cell of origin is perhaps a pre-B cell harboring IGH::BCL2 with the propensity to undergo further genetic alterations in the germinal centers of lymph nodes: does IGH::BCL2 in pre-B cells set off a plasticity cell state? Do FL and LC neoplasms develop separately through a common progenitor or via a multistep process of transdifferentiation or dedifferentiation/redifferentiation? Here, we review the literature and relevant cases presented in the Society for Hematopathology/European Association of Haematopathology 2021 Workshop to better understand this rare and complex phenomenon. We discuss clinical data, clonal relationship, and the mutational profile of these tumors and review proposed mechanisms of B/myeloid conversion based on in vitro and in vivo models.

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Malignant histiocytoses (MHs), or the \'M group\' of the Histiocyte Society classification, are characterized by neoplastic histiocytes with large pleomorphic nuclei. MH encompasses the diagnoses of histiocytic sarcoma, interdigitating dendritic cell sarcoma, and Langerhans cell sarcoma. We aimed to define the phenotypic spectrum of MH and examine the genotypic features across this spectrum. Using immunohistochemistry, we arranged the 22 cases into 4 subtypes that correspond to the lines of differentiation from monocytic and dendritic cell precursors as follows: (1) macrophage (n = 5): CD68+, CD163+, CD14+, and Factor 13a+; (2) monocyte-macrophage (n = 5): CD68+, CD163+, CD14+, S100+, and OCT2+; (3) dendritic cell (n = 6): CD68+, CD11c+, S100+, lysozyme+, ZBTB46+, and CD1a/langerin < 5%; and (4) Langerhans cell (n = 6): CD68+, CD11c+, S100+, ZBTB46+, CD1a+, and langerin+. The phenotypic subtypes align with those seen in low-grade histiocytic neoplasms as follows: MH-macrophage type correlates with Erdheim-Chester disease phenotype; MH-monocyte-macrophage type with Rosai-Dorfman disease phenotype, and MH-Langerhans cell type with Langerhans cell histiocytosis. Activating mutations in MAPK-pathway genes were identified in 80% of MH cases; 29% had mutations in the PI3k-AKT-mTOR pathway and 59% had mutations in epigenetic modulating genes. Strong expression of cyclin D1 was present in all cases, whereas p-ERK and p-AKT were not uniformly expressed. Eight of 22 (36%) MH cases were proven to be clonally related to a prior B-cell lymphoma. Defining the phenotypic spectrum of MH provides a guide to diagnosis and allows further exploration into the potential biological and clinical significance.

Langerhans cell sarcoma (LCS) is a rare malignancy of dendritic cells and usually results in a poor oncological outcome. Thus, LCS is usually given a positive administration. Herein, we presented the first case of primary LCS in the urinary bladder staged T1N0M0 and treated by TURBT and short-term local chemotherapy. Our experience in this unique case may suggest that LCS in the urinary bladder with a non-muscle-invasive stage may be managed according to the treatment model of non-muscle-invasive urothelial carcinoma of the urinary bladder.

UNASSIGNED: Langerhans cell sarcoma (LCS) is an extremely rare type of malignant tumor that originates from Langerhans cells (LC). It is characterized by the malignant proliferation and dissemination of LC and is extremely invasive, with rapid progression and a poor prognosis. Treatment includes resection of lesions, radiotherapy, chemotherapy, immunotherapy, and transplantation of hematopoietic stem cells. However, a unified and optimized treatment plan is lacking, and individualized treatment is accepted.
UNASSIGNED: We report an 18-year-old man with intracranial and extracranial communicative LCS that occurred in only the left forehead without metastasis to other regions. Clinical and hematological data were normal. We undertook complete resection of diseased tissue, which was pathologically examined. Staining (hematoxylin and eosin) showed positivity for cluster of differentiation (CD)1a (++), S-100 protein (++), P53 (++), CD68 (+), cyclin D1 (+), cyclin A (+), cyclin B1 (+), IGF2BP3 (+), and Ki-67 (45%-50%). Recurrence or metastasis were not observed after long-term follow-up.
UNASSIGNED: LCS is a rare malignant tumor, and one that occurs with intracranial and extracranial communication is even rarer. Active adoption of an individualized treatment plan is crucial.

Langerhans cell sarcoma (LCS) is a rare malignant tumor of Langerhans cells and uncommonly involves head and neck regions. Unlike Langerhans cell histiocytosis (LCH), it has an aggressive clinical course with malignant cytological features. Till now, a handful of cases have been reported and the common anatomical sites involved are skin, lymph node, and bone in loco - regional cases and lymph node, lung, liver, spleen, and bone in disseminated disease. Due to its rarity, standard protocols of treatment for these patients are not yet well established. Herein, we report such a case in a 25-year-old male presenting with a bilateral submandibular swelling, which was diagnosed as LCH on Fine Needle Aspiration Cytology (FNAC) and later confirmed to be a case of LCS in histopathological examination and immunohistochemistry. The authors are aware of only a single similar case being reported in the English literature.

Langerhans cell sarcoma (LCS) is a rare high-grade neoplasm of langerhans cell phenotype having unambiguous malignant cytological features. We report such a rare case in a 20-year-old man who presented with dyspnea and high-grade fever. On evaluation, he had generalized lymphadenopathy, hepatosplenomegaly, and a large anterior mediastinal mass. Fine needle aspiration from the mediastinal mass and bone marrow aspirate showed numerous atypical cells, many of which showed grooved nuclei. In addition, the bone marrow showed prominent hemophagocytosis. The patient had a stormy hospital stay and succumbed to the illness. The autopsy revealed a rare multisystem involvement by LCS involving the lymph nodes, liver, spleen, lungs, and intestine, which harbored a BRAFV600E mutation and was associated with hemophagocytosis.