Histiocytic sarcoma as a secondary malignancy: pathobiology, diagnosis, and treatment

One Health: Therapies Targeting Genetic Variants in Human and Canine Histiocytic and Dendritic Cell Sarcomas

The precise cause of HS/DCS is still unknown. The relatively low incidence in humans urges for an animal model with a high incidence to accelerate knowledge about genetics and optimal treatment of HS/DCS. Namely, until now, the therapies targeting genetic variants are still more experimental and sparsely used, while consensus is missing. In addition, the literature about variants and possible mutation-targeted therapies in humans and dogs consists mainly of case reports scattered throughout the literature. Therefore, an overview is provided of all currently known genetic variants in humans and dogs with HS/DCS and its subtypes, their possible mutation-targeted therapies, their efficacy, and a contemplation about the future. Several genetic variants have already been discovered in HS/DCS, of which many are shared between canine and human HS/DCS, but unique variants exist as well. Unfortunately, none of these already found variants seem to be specifically causal for HS/DCS, and the puzzle of its landscape of genetic variation is far from complete. The use of mutation-targeted therapies, including MAPK-/MEK-inhibitors and the future use of PTPN11-, CDK4/6- and PD-1-inhibitors, seems to be promising for these specific variants, but clearly, clinical trials are needed to determine optimal inhibitors and standardised protocols for all variants. It can be concluded that molecular analysis for variants and subsequent mutation-targeted therapy are an essential addition to cancer diagnostics and therapy. A joint effort of humans and dogs in research is urgently needed and will undoubtedly increase knowledge and survival of this devastating disease in dogs and humans.

Clinical, Histopathological and Molecular Spectrum of Cutaneous Lesions in Myelodysplastic Syndrome and Myeloproliferative Neoplasms (MDS/MPN): An Integrative Review

Myeloid neoplasms and acute leukemias include different entities that have been recently re-classified taking into account molecular and clinicopathological features. The myelodysplastic syndrome/myeloproliferative neoplasm (MDS/MPN) category comprises a heterogeneous group of hybrid neoplastic myeloid diseases characterized by the co-occurrence of clinical and pathological features of both myelodysplastic and myeloproliferative neoplasms. The most frequent entity in this category is chronic myelomonocytic leukemia (CMML) which is, after acute myeloid leukemia (AML), the main myeloid disorder prone to develop cutaneous manifestations. Skin lesions associated with myelodysplastic and myeloproliferative neoplasms include a broad clinical, histopathological and molecular spectrum of lesions, poorly understood and without a clear-cut classification in the current medical literature. The aim of this review is to describe and classify the main clinical, histopathological and molecular patterns of cutaneous lesions in the setting of MDS/MPN in order to improve the diagnostic skills of the dermatologists, hematologists and pathologists who deal with these patients.

Favorable outcome of a histiocytic sarcoma patient treated with immune checkpoint inhibitor: a case report

Introduction and Importance

Histiocytic sarcoma (HS) is an extremely rare malignancy in which there has been no standard treatment approach. Some preclinical studies have provided rationales for the application of immunotherapy in advanced HS.

Case Presentation

The authors reported a case of a 61-year-old patient with metastatic HS who had a rapid progression on ifosfamide, carboplatin, and etoposide chemotherapy. The authors performed PD-L1 testing, which showed a strong positivity in 90% of tumor cells. The patient was then treated with pembrolizumab 200 mg every 3 weeks. He refused palliative radiotherapy. A dramatic response in all sites was recorded on the PET-CT scan after three cycles. He was maintained on pembrolizumab, reaching over 30 months without disease progression.

Clinical Discussion

Recent molecular data suggests there could be a role of immunotherapy in HS. In our patient, the disease was refractory to chemotherapy and pembrolizumab has been given based on the strong PD-L1 expression. Response to immunotherapy has also been recorded in several cases with malignant histiocytic neoplasm.

Conclusion

Immunotherapy might bring sustained disease remission in PD-L1 high expression HS and further studies evaluating the role of immune checkpoint inhibitor in this disease are warranted.

Progression in Myeloid Neoplasms: Beyond the Myeloblast

Disease progression in myelodysplastic syndromes (MDS), myelodysplastic-myeloproliferative neoplasms (MDS/MPN), and myeloproliferative neoplasms (MPN), altogether referred to as myeloid neoplasms (MN), is a major source of mortality. Apart from transformation to acute myeloid leukemia, the clinical progression of MN is mostly due to the overgrowth of pre-existing hematopoiesis by the MN without an additional transforming event. Still, MN may evolve along other recurrent yet less well-known scenarios: (1) acquisition of MPN features in MDS or (2) MDS features in MPN, (3) progressive myelofibrosis (MF), (4) acquisition of chronic myelomonocytic leukemia (CMML)-like characteristics in MPN or MDS, (5) development of myeloid sarcoma (MS), (6) lymphoblastic (LB) transformation, (7) histiocytic/dendritic outgrowths. These MN-transformation types exhibit a propensity for extramedullary sites (e.g., skin, lymph nodes, liver), highlighting the importance of lesional biopsies in diagnosis. Gain of distinct mutations/mutational patterns seems to be causative or at least accompanying several of the above-mentioned scenarios. MDS developing MPN features often acquire MPN driver mutations (usually JAK2), and MF. Conversely, MPN gaining MDS features develop, e.g., ASXL1, IDH1/2, SF3B1, and/or SRSF2 mutations. Mutations of RAS-genes are often detected in CMML-like MPN progression. MS ex MN is characterized by complex karyotypes, FLT3 and/or NPM1 mutations, and often monoblastic phenotype. MN with LB transformation is associated with secondary genetic events linked to lineage reprogramming leading to the deregulation of ETV6, IKZF1, PAX5, PU.1, and RUNX1. Finally, the acquisition of MAPK-pathway gene mutations may shape MN toward histiocytic differentiation. Awareness of all these less well-known MN-progression types is important to guide optimal individual patient management.

Histiocytic Sarcoma Secondary to Gastrointestinal Stromal Tumors: A Literature Review

Histiocytic sarcoma (HS) is a rare tumor that may result from the transdifferentiation of preexisting hematolymphoid neoplasms in a subset of patients. There are instances of correlation or concurrence between HS and a number of cancers, particularly B-cell-associated hematopoietic tumors. Only three cases of HS occurring subsequent to or concurrently with gastrointestinal stromal tumors (GIST) have been recorded. Our main objective was to give an overview of demographics, clinical signs and symptoms, histopathological findings, and immunohistochemical and molecular analysis when HS develops secondary to or concurrently with GIST. A search of PubMed, Google Scholar, and ScienceDirect was undertaken using Medical Subject Headings (MeSH) keywords. According to the findings of our review, there were two males (66.6%) and one female (33.3%). The average age of patients at presentation was 59.6 years. On the immunohistochemistry, three patients were positive for cluster of differentiation (CD) 68 (100%), two patients were positive for CD 163 (67%), one patient was positive for leukocyte common antigen (LCA) (33%), and only one patient was positive for CD 4, CD 10, CD 31, CD 45, human leukocyte antigen (HLA)-DR, lysozyme, and vimentin (33%). On molecular investigation, the gastric mass of only one patient (33.33%) contained a KIT mutation on exon 11. Emperipolesis was observed in one patient (33.33%) on histological examination. Our study provides an important overview of the available literature and gives insight into important diagnostic markers of HS when it occurs secondary to or concurrently with GIST.

Multiple disciplinary team management of rare primary splenic malignancy: Two case reports

BACKGROUND

Malignant splenic tumors are rare but fatal, presenting a challenge in diagnosis and management involving hematology, oncology, and general surgery. By contrast, diagnosing and treating other common malignant tumors (such as lung and gastrointestinal cancer) offers multiple strategies for chemotherapy, radiotherapy, targeted therapy, and immunotherapy with the prospect of a cure. With various specialists involved in clinical multiple disciplinary team (MDT) discussion, personal bias can be minimized. It can also ignite important discussion which can benefit not only one patient but many patients.

CASE SUMMARY

Here, we report on the MDT diagnosis and management of the malignant splenic tumors littoral cell angiosarcoma and histiocytic sarcoma. Although only two cases of rare primary splenic malignancy are presented, MDT is a novel means of rare disease treatment.

CONCLUSION

To benefit patients, imaging analysis, safe operation, precise pathology examination, and individualized therapeutic treatment strategies are required. The involvement of various specialists in a clinical MDT discussion minimizes personal bias and can create important ideas to benefit all patients.

Liver cancer concurrent with chronic myelocytic leukemia and extreme thrombocytosis: a rare case report

Chronic myelocytic leukemia (CML) can occasionally occur after long-term chemotherapy for solid tumors; solid tumors secondary to chemotherapy and biotherapy for CML have also been reported. However, concurrence of these two phenomena in an untreated patient has seldom been reported. Herein, we describe the case of a female patient in her early 60 s who was transferred to the liver surgery department after the discovery of a large liver mass and elevated plasma alpha-fetoprotein levels. She was initially diagnosed with liver cancer. Blood tests indicated an increased platelet count (2464 × 10⁹/L). Chromosomal examination from a bone marrow biopsy indicated the presence of the t(9;22) translocation, and subsequent fluorescence in situ hybridization and PCR were positive for the BCR-ABL rearrangement. A diagnosis of CML was made. The patient received hydroxyurea and imatinib to treat CML and underwent subsequent platelet-lowering therapy and a liver biopsy, which suggested moderately poorly differentiated adenocarcinoma or potentially hepatic metastatic carcinoma. However, the patient refused further pathological examination or screening for the site of the primary tumor. She died 6.5 months after discharge. The exact relationship between the two tumors remains unclear, and more patients need to be evaluated.

Application of PD‑L1 blockade in refractory histiocytic sarcoma: A case report

Histiocytic sarcoma (HS) is a rare hematological malignancy, which exhibits morphological and immunophenotypic features of histiocytes. A standard therapy for HS has not yet been established due to its rareness; therefore, disease control is not always possible. A multimodal treatment strategy has been suggested for HS. The present study reported on a case of a 43-year-old female patient who complained of left femoral pain, which was caused by left femoral bone mass. A biopsy of their left femoral bone tumor revealed that the patient had HS. Their sarcoma was localized in the femoral bone and was not considered to be curable, due to local infiltration of the bone tumor beyond the periosteum. The patient then underwent two types of HS-specific chemotherapy; however, both regimens were ineffective. As a result, they underwent radiation therapy at the sites of progressive disease. Because the HS cells of the patient expressed PD-L1, they were treated with nivolumab (240 mg/body, biweekly) for residual diseases in the right occipital bone, multiple lung nodules, intrapelvic right lymph node and primary site. Nivolumab treatment resulted in a complete response at all sites, with the exception of the primary site, which was confirmed by ¹⁸F-fluorodeoxyglucose-positron emission tomography/computed tomography. The patient received additional nivolumab treatment as consolidation therapy for 1 year. In addition, residual disease of the femoral head was completely resected. The surgically resected refractory tumor revealed the tumor cells no longer pathologically expressed PD-L1 . In conclusion, for refractory and recurrent HS in which surgical resection is not appropriate, treatment with immune-checkpoint inhibitors, such as nivolumab, may be considered an optional but promising immunotherapy if the tumor histologically expresses PD-L1. The present study detected one of the refractory mechanisms of ICI treatment.

Histiocytic Sarcoma: Clinical Features and Outcomes of Patients Treated at a Tertiary Cancer Care Center

Histiocytic sarcoma (HS) is an extremely rare histiocytic disorder of unknown etiology. It is not a true sarcoma and is named so, due to the pathological resemblance to mature histiocytes. The clinical presentation of HS is diverse and is related to the involved organs. Due to its aggressive nature, with poor prognosis and lack of a standard treatment regimen of choice, its diagnosis and management pose a challenge to the clinician. Limited literature is available on the management of this entity. Here, we report four patients with HS, diagnosed over 15 years in a tertiary cancer center, with varied clinical presentation, management, and outcomes. The first patient presented with a localized unresectable esophageal mass. He was treated with cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) combination chemotherapy and attained complete remission. The second patient had a painless mass of the hand, treated with wide excision and adjuvant Radiotherapy. She is disease-free for the past 12 years. The third patient had presented with an anterior mediastinal mass. He had progressive disease on chemotherapy. The fourth patient had multifocal disease with generalized lymphadenopathy. She was treated with CHOP chemotherapy and is now disease-free at 13 months. To summarize, the patients with the localized resectable disease did well, with surgical excision and adjuvant radiotherapy, while patients with the multifocal disease did well on CHOP chemotherapy. The take-home message from this case series is - CHOP off whenever you can and if not give CHOP to chop off the disease.

A case of primary histiocytic sarcoma arising from a neck lymph node

Histiocytic sarcoma (HS) is an aggressive and rare hematological malignancy. Its treatment has not been established, and most patients die within 2 years of diagnosis. Resection can provide a favorable prognosis for solitary lesions. We present the case of an 80-year-old Japanese man with HS. He presented a history of a slow-growing painless mass in the lower part of his right jaw. Ultrasonography showed a swollen lymph node in the vicinity of the right submandibular gland. Contrast-enhanced computed tomography revealed a heterogeneous, low-contrast mass on the right of the neck. Magnetic resonance imaging revealed a heterogeneously enhanced mass in gadolinium-enhanced T1-weighted images. The fine needle biopsy showed spindle-shaped cells and HS was suspected. Fluorodeoxyglucose positron emission tomography revealed uptake by the tumor alone. The patient underwent right upper neck dissection and resection of the submandibular salivary glands. No postoperative adjuvant treatment was administered, but 2-year survival was achieved. Histopathological examination showed proliferation of large, pleomorphic atypical cells without differentiation into lymphocytes, which proved their differentiation into histiocytes. A bone marrow biopsy showed no evidence of monocytic leukemia. Thus, a diagnosis of HS was made. With local treatment alone, our patient achieved long-term survival, maintaining his quality of life.

Increased tumor-infiltrating lymphocyte density is associated with favorable outcomes in a comparative study of canine histiocytic sarcoma

Histiocytic sarcoma (HS) is a rare and aggressive tumor in humans with no universally agreed standard of care therapy. Spontaneous canine HS exhibits increased prevalence in specific breeds, shares key genetic and biologic similarities with the human disease, and occurs in an immunocompetent setting. Previous data allude to the immunogenicity of this disease in both species, highlighting the potential for their successful treatment with immunotherapy. Quantification of CD3 tumor-infiltrating lymphocytes (TIL) in five cases of human HS revealed variable intra-tumoral T cell infiltration. Due to the paucity of human cases and lack of current model systems in which to appraise associations between anti-tumor immunity and treatment-outcome in HS, we analyzed clinical data and quantified TIL in 18 dogs that were previously diagnosed with localized HS and treated with curative-intent tumor resection with or without adjuvant chemotherapy. As in humans, assessment of TIL in biopsy tissues taken at diagnosis reveal a spectrum of immunologically "cold" to "hot" tumors. Importantly, we show that increased CD3 and granzyme B TIL are positively associated with favorable outcomes in dogs following surgical resection. NanoString transcriptional analyses revealed increased T cell and antigen presentation transcripts associated with prolonged survival in canine pulmonary HS and a decreased tumor immunogenicity profile associated with shorter survivals in splenic HS. Based on these findings, we propose that spontaneous canine HS is an accessible and powerful novel model to study tumor immunology and will provide a unique platform to preclinically appraise the efficacy and tolerability of anti-cancer immunotherapies for HS.

Successful Treatment of Incidental Histiocytic Sarcoma Concomitant with Laryngeal Carcinoma

Histiocytic sarcoma (HS) is an extremely rare non-Langerhans cell disorder with an aggressive course and limited treatment options. HS most often presents at an advanced clinical stage, with a limited response to chemotherapy and high mortality. No standard treatment has been established for HS. We herein describe the first case of HS concomitant with laryngeal carcinoma that was promptly diagnosed and successfully treated; the condition of the patient has remained stable for 4 years with no recurrence.

Disseminated mucocutaneous trichosporonosis in a patient with histiocytic sarcoma

Trichosporon asahii is the causal agent of trichosporonosis. Patients with immunosuppression or hematological malignancies are at higher risk of infection. Skin and mucosal involvement appear as fast-growing papulonodular lesions and necrotic ulcers. Internal organ dissemination is lethal. Therapeutic success depends on the underlying disease. Here, the authors present the first case of disseminated mucocutaneous trichosporonosis in a patient with a post-mortem diagnosis of histiocytic sarcoma, a rare and aggressive haematolymphoid neoplasm. Regretfully, death occurred despite treatment with liposomal amphotericin B and supportive measures, showcasing the fatality of both diseases.

A Pedigree Analysis and Clonal Correlations of the Coexistence of B-Cell Lymphoma and Histiocytic/Dendritic Cell Tumor

Histiocytic/dendritic cell tumors are rare in clinical practice. It is postulated that they originate from bone marrow stem cells. Accumulating evidence has established the existence of immunoglobulin gene and T-cell receptor gene rearrangements in these tumors. Cases of transdifferentiation across lineages from follicular lymphoma to histiocytic/dendritic cell tumors have also been reported. Herein, we report 2 adult males with histiocytic neoplasms coexisting with B-cell lymphoma. Laser capture microdissection and capillary electrophoresis polymerase chain reaction analysis revealed comparable immunoglobulin gene rearrangement in both patients. In one case, chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), Langerhans cell sarcoma, and histiocytic sarcoma coexisted in the lymph nodes. 11q22 deletion often present in CLL/SLL and expression of the BRAF V600E gene was detected in all the 3 components. In the other case, there diffuse large B-cell lymphoma and histiocytic sarcoma coexisted in the spleen. Forty-seven mutated genes commonly found in B-cell lymphoma were detected by next-generation sequencing. In the same line, DTX1, IRF8, KMT2D, MAP2K1, and TET2 genes were found to have similar mutation sites. The results of this study will contribute in providing new ideas for targeted treatment of these diseases.

A Rare Case of Histiocytic Sarcoma Secondary to Gastrointestinal Stromal Tumor in the Stomach: Transdifferentiation or Synchronicity?

Histiocytic sarcoma is a rare malignant histiocytic neoplasm composed of cells with morphologic and immunophenotypic features of mature tissue histiocytes. It occurs anywhere in the body and behaves aggressively. However, its etiology is unknown. Here, we report a 68-year-old female who developed histiocytic sarcoma following chemotherapy with imatinib (Gleevec) for gastrointestinal stromal tumor. Possible mechanisms of transdifferentiation from gastrointestinal stromal tumor to histiocytic sarcoma are discussed based on the features of our case and other two similar cases in the literature.

Case Report: Myeloid Sarcoma Development During Treatment for B Cell Lymphoblastic Lymphoma in a Boy with KRAS/NRAS Gene Mutations

Here, we report a rare case of a 12-year-old boy who was initially diagnosed with B cell lymphoblastic lymphoma (BLBL) and developed myeloid sarcoma (MS) eight months after chemotherapy. Next-generation sequencing (NGS) showed mutations of KRAS and NRAS genes in both the bone marrow and lymph node. He presented an abnormal karyotype of 46, XY, -9, der (16) t (9; 16) (q13; q12), +mar. He received chemotherapy according to the South China Children's Leukemia Group 2016 protocol. Complete remission was achieved by the 15th day post-treatment. Eight months later and immediately prior to the start of maintenance therapy, the patient developed fever, skin nodules in both upper arms, and enlargement of bilateral testes. Pathological analysis of skin and testicular biopsies suggested the diagnosis of myeloid sarcoma (MS). Again, NGS examination showed mutations of KRAS and NRAS genes. The patient underwent haploidentical hematopoietic stem cell transplantation but unfortunately did not survive. The interval of eight-month interval between the initial disease onset and MS brings into question whether MS developed as part of the initial onset of disease or as a secondary tumor in association with chemotherapy. Thus, understanding the pathogenesis of MS involving abnormalities of lymphoid progenitors may assist in the prediction of prognosis and development of novel target therapies.

Histiocytic and dendritic cell neoplasms: Reappraisal of a Japanese series based on t(14;18) and neoplastic PD-L1 expression

Histiocytic and dendritic cell (H/DC) neoplasms are heterogeneous, originating from myeloid- or stromal-derived cells. Multiple reports describe the cross-lineage transdifferentiation of neoplastic B cells into H/DC neoplasms. Most such cases are from Western countries, and rarely from Japan or East Asia. Here we report 17 cases of H/DC neoplasms in Japanese patients, with analysis of t(14;18) by fluorescence in situ hybridization, and of neoplastic programmed death-ligand 1 (PD-L1) expression by immunostaining (clones SP142, E1J2J, and 28-8). These 17 cases were diagnosed according to the 2017 World Health Organization (WHO) classification, and included two histiocytic sarcomas (HS), two interdigitating cell (IDC) sarcomas, one Langerhans cell sarcoma, two dendritic cell sarcomas, and 10 follicular dendritic cell (FDC) sarcomas. No case had any past history of follicular lymphoma (FL). Two cases of HS and one IDC sarcoma, all of which were myeloid-driven, were found to exhibit t(14;18). In the latter case, at 30 months after IDC sarcoma diagnosis, FL development was detected. Three (30%) FDC sarcoma cases exhibited neoplastic PD-L1 expression with all the three PD-L1 antibody clones. This is the first report of t(14;18) and neoplastic PD-L1 expression on H/DC neoplasms among Japanese patients, each of which appeared to be associated with HS and FDC sarcoma, respectively.

Progression, transformation, and unusual manifestations of myelodysplastic syndromes and myelodysplastic-myeloproliferative neoplasms: lessons learned from the XIV European Bone Marrow Working Group Course 2019

Disease progression in myelodysplastic syndromes (MDS) and myelodysplastic-myeloproliferative neoplasms (MDS/MPN) is a major source of mortality. The European Bone Marrow Working Group organized a dedicated workshop to address MDS and MDS/MPN progression, and myeloid neoplasms with histiocytic and lymphoblastic outgrowths in 2019 in Frankfurt, Germany. In this report, we summarize clinical, histopathological, and molecular features of 28 cases. Most cases illustrate that prognostic mutational profiles change during follow-up due to accumulation of high-risk mutations in the trunk clone, and that results from repeated molecular testing can often explain the clinical progression, suggesting that regular genetic testing may predict transformation by early detection of aggressive clones. Importantly, identical mutations can be linked to different clinical behaviors or risks of fibrotic progression and/or transformation in a context-dependent manner, i.e., MDS or MDS/MPN. Moreover, the order of mutational acquisition and the involved cell lineages matter. Several cases exemplify that histiocytic outgrowths in myeloid neoplasms are usually accompanied by a more aggressive clinical course and may be considered harbinger of disease progression. Exceptionally, lymphoblastic transformations can be seen. As best estimable, the histiocytic and lymphoblastic compounds in all occasions were clonally related to the myeloid compound and-where studied-displayed genomic alterations of, e.g., transcription factor genes or genes involved in MAPK signaling that might be mechanistically linked to the respective type of non-myeloid outgrowth.

Primary Histiocytic Sarcoma Presenting as a Breast Mass: A Case Report

Histiocytic sarcoma is a rare hematologic malignancy, with very few cases of primary histiocytic sarcoma of the breast described in English scientific literature. Herein, we describe a case of primary histiocytic sarcoma of the breast in a 75-year-old woman, with no clinical history of malignant tumors, who presented with a palpable solitary breast mass. Microscopically, the resected breast mass showed large pleomorphic cells, some multinucleated giant cells, and admixed inflammatory components. The pleomorphic tumor cells further showed a diffuse, noncohesive growth pattern, an abundant eosinophilic cytoplasm, and strong and diffuse immunoreactivity for cluster of differentiation (CD) 68 and CD163. Furthermore, a whole-body positron-emission tomography/computed tomography using deoxy-2-[¹⁸F]fluoro-D-glucose performed after surgery showed no other masses or lesions. After surgical excision, the patient was followed up, and no evidence of tumor recurrence or metastasis was noted.

A Case of Histiocytic Sarcoma Arising from Mycosis Fungoides

Histiocytic sarcoma (HS) is an uncommon malignant neoplasm arising from mature histiocytes and most commonly characterized by the immunophenotypic expression of CD68, CD163, or lysozyme. Although rare, HS arising as a second primary malignancy following hematolymphoid neoplasms has been reported. To our knowledge, this is the first reported case of HS occurring as a second primary malignancy in a patient with mycosis fungoides (MF), with the retained immunophenotype markers CD30 and CD4.

Combined Tumors in Hematolymphoid Neoplasms: Case Series of Histiocytic and Langerhans Cell Sarcomas Arising From Low-Grade B-Cell Lymphoma

We report an index case of histiocytic sarcoma arising in a 70-year-old patient with long-standing chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL). The patient presented in 2017 with painful, enlarging swelling of the left neck. He had remote history of cutaneous squamous cell carcinoma with no sign of recurrence, and his CLL/SLL was thought to be in remission. Computed tomography showed mild splenomegaly and multifocal lymphadenopathy including a 3-cm left neck mass. Biopsy of the left neck mass showed CLL/SLL with associated histiocytic sarcoma. Flow cytometry demonstrated a B cell neoplasm with CLL/SLL phenotype. Despite radiation therapy, he expired 3 months after presentation. Two similar cases (CLL/SLL and histiocytic sarcoma, follicular lymphoma and Langerhans cell sarcoma) from another institution are also illustrated. The pathological features of combined tumors in lymphoid neoplasms, a general framework to the work-up to determine interrelatedness of tumor components, and the clinical relevance are discussed.

Identification of diverse activating mutations of the RAS-MAPK pathway in histiocytic sarcoma

Recent studies have demonstrated recurrent activating mutations involving the classical MAPK and PI3K signaling pathways in a large proportion of histiocytic neoplasms, such as Langerhans cell histiocytosis. However, very little is known about the molecular genetics of histiocytic sarcoma, a rare aggressive malignant neoplasm that shows pathologic characteristics of mature macrophages. Here we report the genomic characteristics of a large cohort of histiocytic sarcomas (n = 28) using a targeted next-generation sequencing approach to identify driver alterations. We identified recurrent mutations involving the RAS-MAPK signaling pathway (MAP2K1, KRAS, NRAS, BRAF, PTPN11, NF1, CBL) in a majority (57%) of histiocytic sarcoma cases and report a clinical response to a MEK inhibitor (Cobimetinib) in a patient with a NF1-mutated histiocytic sarcoma. A smaller subset of cases (21%) also showed mutations resulting in activation of the PI3K signaling pathway (PTEN, MTOR, PIK3R1, PIK3CA). In addition, the tumor-suppressor gene CDKN2A was the most frequently altered gene (46%). Further, a subset of histiocytic sarcoma cases shows striking molecular genetic similarities to B cell lymphomas, supporting a clonal relationship between B cell neoplasms and a subset of histiocytic sarcomas. These findings support a cooperative role for MAPK, PI3K, and cyclin-CDK4/6-INK4 signaling in the pathogenesis of histiocytic sarcoma and provide a rational basis for targeting these pathways.

Putative histiocytic sarcoma in redfin needlefish Strongylura notata (Beloniformes: Belonidae) in Florida, USA

Redfin needlefish Strongylura notata from Florida coastal waters were observed with unusual neoplastic lesions. Affected specimens were collected from 1 Atlantic estuary (Indian River Lagoon, prevalence = 0.32%, n = 5314) and 2 Gulf of Mexico estuaries (Tampa Bay, prevalence = 0.02%, n = 10762; Charlotte Harbor, prevalence = 0.02%, n = 5112) during routine fisheries-independent monitoring surveys conducted from 1999-2009. Grossly, each lesion manifested as a large (18-30 mm × 20-50 mm), raised (approximately 10 mm), white, creamy, or pinkish nodule on the flank, dorsal trunk, base of the pectoral fin, or head. Multiple small (<5 mm) nodules possessing poorly demarcated borders with neighboring tissues on the external jaw surface and at the base of the teeth were also observed. Histopathologically, neoplastic cells were found in the dermis, beneath the skeletal muscle, and in the soft tissue at the base of teeth of the premaxilla and the dentary jaw processes. Neoplastic cells usually had prominently invaded among the myosepta of the skeletal muscle. Neoplastic parenchymal cells had the basic characteristics of atypical, mononuclear, round, histiocytic cells with an eccentric, reniform nucleus and abundant cytoplasmic vacuolation, while some exhibited bizarre nuclear pleomorphism. Transmission electron microscopy revealed that neoplastic cells had a grooved nucleus and cytoplasmic organelles with rough endoplasmic reticulum, mitochondria, Golgi apparatus, and lysosomes. Neoplastic cells had possibly metastasized to liver, spleen, and kidney. Positive immunohistochemical staining with Ki67, p53, S-100, and CD163 support neoplastic features and a putative diagnosis of histiocytic sarcoma.

Histiocytic Sarcoma: Review, Discussion of Transformation From B-Cell Lymphoma, and Differential Diagnosis

Context.—

Histiocytic sarcoma is a rare neoplasm of mature histiocytes with an aggressive clinical course that can arise de novo or from a low-grade B-cell lymphoma. In particular, chronic lymphocytic leukemia/small lymphocytic lymphoma is a very common malignancy in the Western hemisphere, and most cases of chronic lymphocytic leukemia/small lymphocytic lymphoma have an indolent course and behavior. However, 2% to 8% of chronic lymphocytic leukemia/small lymphocytic lymphoma cases transform. Histiocytic sarcomatous transformation is rare and portends poor prognosis.

Objective.—

To review the clinical features, morphology, and key points related to the differential diagnosis for histiocytic sarcoma. We discuss recent understanding of the biology underlying transformation.

Data Sources.—

University of Michigan case and review of pertinent literature about histiocytic sarcoma and morphologic differential diagnosis.

Conclusions.—

Histiocytic sarcoma is a rare histiocytic neoplasm that can arise as a result of transdifferentiation from low-grade B-cell lymphomas, and has a wide differential diagnosis including other histiocytic/dendritic cell neoplasms, myeloid neoplasms, lymphomas, melanoma, and carcinoma. However, some key morphologic and immunohistochemical features allow for accurate classification.

Histiocytic cell neoplasms involving the bone marrow: summary of the workshop cases submitted to the 18th Meeting of the European Association for Haematopathology (EAHP) organized by the European Bone Marrow Working Group, Basel 2016

The bone marrow is a preferential site for both reactive and neoplastic histiocytic proliferations. The differential diagnosis ranges from reactive histiocyte hyperplasia in systemic infections, vaccinations, storage diseases, post myeloablative therapy, due to increased cell turnover, and in hemophagocytic lymphohistiocytosis, through extranodal Rosai-Dorfman disease to neoplasms derived from histiocytes, including histiocytic sarcomas (HS), Langerhans cell histiocytoses (LCH), Erdheim-Chester disease (ECD), and disseminated juvenile xanthogranuloma (JXG). One of the most important recent developments in understanding the biology of histiocytic neoplasms and in contributing to diagnosis was the detection of recurrent mutations of genes of the Ras/Raf/MEK/ERK signaling pathway, in particular the BRAF^V600E mutation, in LCH and ECD. Here, we summarize clinical and pathological findings of 17 histiocytic neoplasms that were presented during the bone marrow symposium and workshop of the 18th European Association for Haematopathology (EAHP) meeting held in Basel, Switzerland, in 2016. A substantial proportion of these histiocytic neoplasms was combined with clonally related lymphoid (n = 2) or myeloid diseases (n = 5, all ECD). Based on the latter observation, we suggest excluding co-existent myeloid neoplasms at initial staging of elderly ECD patients. The recurrent nature of Ras/Raf/MEK/ERK signaling pathway mutations in histiocytic neoplasms was confirmed in 6 of the 17 workshop cases, illustrating their diagnostic significance and suggesting apotential target for tailored treatments.

[Histiocytic and dendritic cell neoplasms: Review of the literature]

Histiocytic and dendritic cell neoplasms (HDN) are rare and their biology, prognosis, treatment and terminology are still under discussion. They are composed of macrophage and dendritic-derived cells and show a wide range of clinical, morphological and prognostic features. Clinicopathological correlation and a broad immunohistochemical panel are required to establish a correct diagnosis. After the detection of BRAF mutations in Langerhans cell histiocytosis, the potential role of other molecular alterations is being studied. We have reviewed the literature published in the last 10 years to provide an overview of NHD, with particular emphasis their molecular features.

Histiocytic sarcoma in a child-successful management and long-term survival with cytoreductive surgery and hyperthermic intraperitoneal chemotherapy

Histiocytic sarcoma is an extremely rare tumor in children. It may occur sporadically or in association with other hematological malignancies. It arises most commonly in the lymph nodes but may occur anywhere in the body and clinical presentation is usually with advanced disease. Following tissue diagnosis and staging, management is with chemotherapy though there are no standard regimes. Surgery has been used successfully for local control. This is the first description of the use of peritonectomy and hyperthermic intraperitoneal chemotherapy to treat histiocytic sarcoma. The 4-year-old patient has been disease free for 6 years.

High frequency of clonal IG and T-cell receptor gene rearrangements in histiocytic and dendritic cell neoplasms

The 2008 World Health Organization (WHO) diagnostic criteria of histiocytic and dendritic cell neoplasms from hematopoietic and lymphoid tissues no longer required the absence of clonal B-cell/T-cell receptor gene rearrangements. It is true that the clonal B-cell/T-cell receptor gene rearrangements have been identified in rare cases of histiocytic and dendritic cell neoplasms, such as those with or following lymphoma/leukemia or in some sporadic histiocytic/dendritic cell sarcomas, but the clonal features of such group of tumor are still not clear. Here we investigated the clonal status of 33 samples including Langerhans cell histiocytosis (LCH), Langerhans cell sarcoma (LCS), follicular dendritic cell sarcoma (FDCS), interdigitating dendritic cell sarcoma (IDCS) and histiocytic sarcoma (HS). Among them, twenty-eight cases were sporadic without current or past lymphoma/leukemia. Three cases were found with a past history of T-cell lymphoma, one case was followed by extraosseous plasmacytoma, and one case was found with diffuse large B-cell lymphoma (DLBCL). Our results showed that there was a high frequency of clonal IG and T-cell receptor gene rearrangements in these cases. Notably, 4 cases of LCH and 2 cases of FDCS showed both B and T cell receptor gene rearrangements concurrently. One case of FDCS synchronous with DLBCL showed identical clonal IGH in both tumor populations and clonal TCRβ in FDCS alone. No matter if the presence of clonal receptor gene rearrangements was associated with the tumor origin or tumorigenesis, it might serve as a novel tumor marker for developing target therapy.

Myeloid transformation of plasma cell myeloma: molecular evidence of clonal evolution revealed by next generation sequencing

Background

Plasma cell myeloma (PCM) is a neoplasm of terminally differentiated B lymphocytes with molecular heterogeneity. Although therapy-related myeloid neoplasms are common in plasma cell myeloma patients after chemotherapy, transdifferentiation of plasma cell myeloma into myeloid neoplasms has not been reported in literature. Here we report a very rare case of myeloid neoplasm transformed from plasma cell myeloma.

Case presentation

A 60-year-old man with a history of plasma cell myeloma with IGH-MAF gene rearrangement and RAS/RAF mutations developed multiple soft tissue lesions one year following melphalan-based chemotherapy and autologous stem cell transplant. Morphological and immunohistochemical characterization of the extramedullary disease demonstrated that the tumor cells were derived from the monocyte-macrophage lineage. Next generation sequencing (NGS) studies detected similar clonal aberrations in the diagnostic plasma cell population and post-therapy neoplastic cells, including IGH-MAF rearrangement, multiple genetic mutations in RAS signaling pathway proteins, and loss of tumor suppressor genes. Molecular genetic analysis also revealed unique genomic alterations in the transformed tumor cells, including gain of NF1 and loss of TRAF3.

Conclusion

To our knowledge, this is the first case of myeloid sarcoma transdifferentiated from plasma cell neoplasm. Our findings in this unique case suggest clonal evolution of plasma cell myeloma to myeloma neoplasm and the potential roles of abnormal RAS/RAF signaling pathway in lineage switch or transdifferentiation.

A "Yellow Submarine" in Dermoscopy

BACKGROUND

Histiocytic sarcoma (HS) is an extremely rare, non-Langerhans cell tumor. HS affects especially adults, its etiology is unknown yet. Skin could be interested by papules or nodules, single or multiple.

CASE REPORT

A Caucasian man in his late 40s came to our clinic for a naevi evaluation. During the visit, a rose papulonodular lesion was observed in the lumbar region. This lesion was completely asymptomatic, and it had been there for an indefinite period. The clinical evaluation revealed that the lesion appeared elevated, of 9 x 15 mm in dimension, symmetrical and of a homogeneous pinkish colour. The videodermoscopical evaluation revealed a homogeneous yellow central pattern, polymorphic vessels, an eccentric peripheral pigmentation and a white collar. An excisional biopsy was performed. The morphology and the expression of CD163, CD68 and/or lysozyme to the immunophenotypic analysis, revealed the true nature of the lesion.

CONCLUSION

HS is usually diagnosed at an already advanced clinical stage and it has a high mortality rate even today. Dermoscopy, showing a yellow and distributed homogeneously colour, can facilitate its hard diagnosis.

Pediatric intracerebral histiocytic sarcoma with rhabdoid features: Case report and literature review

A 16-year-old boy presented with marked weight loss, weakness of the left extremities and dizziness of 2 months duration and vomiting for 2 days. Brain MRI showed an approximately 6.5 × 5.3 cm-sized huge heterogeneous enhancing mass located in the corpus callosum, extending into the lateral ventricle. Open biopsy showed that the lesion consisted of lymphoplasmacytes and plump histiocytes with rhabdoid morphology, which were stained with S-100 protein, CD68 (KP1) and negative for CD1a. Histiocytic tumor was initially diagnosed. Chemotherapy using methotrexate, 6-mercaptopurine, vinblastine, interferon-alpha and dexamethasone was performed. After 5 months, partial removal was done. Microscopically, plump and bizarre tumor cells as well as rhabdoid features were found. Occasional spindle cells and necrosis were also found. These cells were positive for CD163, CD68, lysozyme, CD4, INI-1 and BRG1. BRAF V600E mutation was detected. The lesion was finally diagnosed as histiocytic sarcoma. Radiotherapy (6000 cGy in 30 fractions) was done. Both cerebral and extracerebral histiocytic sarcomas have long been diagnosed by unclarified criteria; its rarity as well as previously unclarified criteria can easily lead to a misinterpretation. Histiocytic sarcoma of the CNS is exceptionally rare in children, associated with an exceptionally poor prognosis. To date, only seven cases of pediatric cerebral histiocytic sarcomas have been reported. The present case is the first pediatric case showing BRAF V600E-mutated intracerebral histiocytic sarcoma.

Histiocytic and dendritic cell neoplasms: what have we learnt by studying 67 cases

Tumors derived from histiocytic and dendritic cells encompass a large and heterogeneous group of neoplastic and reactive conditions, and their diagnosis is challenging both for pathologists and clinicians. Diagnosis is based on morphological and phenotypical findings, but hybrid features are not uncommon. Furthermore, recent studies uncovered the molecular mechanisms driving some of these tumors, improving diagnostic adequacy, and providing the basis for effective therapeutic breakthroughs.Sixty-seven cases were submitted to the accessory cell and histiocytic neoplasms session at the European Association of Haematopathology/Society for Hematopathology workshop 2016 held in Basel, Switzerland. The cases included histiocytic sarcomas (HS), Langerhans cell tumors (LCT), Erdheim-Chester disease, interdigitating dendritic cell sarcomas (IDCS), indeterminate dendritic cell tumors (IND-DCT), follicular dendritic cell sarcomas, and blastic plasmacytoid dendritic cell neoplasms. Rosai-Dorfman disease and, more rare, conditions such as ALK-positive histiocytosis were also submitted. These cases illustrated classical and unexpected features at morphological, phenotypical, and molecular levels, providing a valuable compendium for pathologists confronting with these tumors.The paper summarizes the most notable features of every single group of diseases, with comments about the most challenging issues, in the attempt to provide practical indications for their recognition.

BRAF V600E expression in histiocytic sarcoma associated with splenic marginal zone lymphoma: a case report

Background

Histiocytic sarcoma is a rare histiocytic neoplasm of unknown etiology that constitutes less than 1% of hematologic malignancies. A few cases of histiocytic sarcoma harboring the BRAF^V600E mutation have been reported, but this finding has not been confirmed in all studies.

Case presentation

We report the case of a 63-year-old white woman with a history of splenic marginal zone lymphoma who presented with 2 weeks of right-sided neck swelling. Positron emission tomography revealed an intensely hypermetabolic and destructive soft tissue mass in her right skull base. A bone marrow biopsy was performed, which revealed an infiltrate of malignant cells characterized as large pleomorphic cells with frequent folded/irregular nuclei, variably prominent nucleoli, fine chromatin, and abundant amounts of eosinophilic cytoplasm. The malignant cells were positive for CD163, CD68 (granular), lysozyme (granular), CD4, and CD45 (partial). Based on the biopsy findings, she was diagnosed as having histiocytic sarcoma. The malignant cells tested positive for the BRAF^V600E protein using immunohistochemistry. Before treatment of her histiocytic sarcoma could be initiated, she developed disseminated intravascular coagulation and acute hypoxemic respiratory failure secondary to non-cardiogenic pulmonary edema. She decided to pursue comfort care and died in our hospital 2 weeks following admission.

Conclusions

Our case illustrates the aggressive nature of histiocytic sarcoma, and provides rare evidence that histiocytic sarcoma associated with indolent lymphomas may harbor the BRAF^V600E mutation. Further research is needed to clarify the role of targeted therapies such as vemurafenib in the treatment of patients with this disorder.

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.

Histiocytic sarcoma with bladder involvement: Case report and literature review

We report an unusual case of histiocytic sarcoma with bladder involvement. An 80 year-old man with a previous history of diffuse large B-cell malignant lymphoma presented with hematuria and back pain. Serial urine cytologies revealed no urothelial malignant cells, but cystoscopy showed a large intravesical mass. The patient underwent transurethral resection (TUR) of the tumor. The bladder TUR specimen showed a widely infiltrating epithelioid neoplasm, with intense immunohistochemical positivity for CD45 and histiocytic markers (CD68, lysozime and fascin). Histopathological diagnosis was histiocytic sarcoma. As the patient's condition was progressively deteriorating, only palliative care was indicated and he died one month after TUR. Although histiocytic sarcoma can often be widespread at the time of diagnosis, to our knowledge, this is the first report of a case presenting with urinary symptoms. Histiocytic sarcoma can mimic many other malignant lesions, and only immunohistochemistry can define the tumor cells, allowing correct therapy. We discuss the differential diagnosis and possible associations.