miRNA expression profiling divides follicular dendritic cell sarcomas into two groups, related to fibroblasts and myopericytomas or Castleman's disease

Follicular dendritic cell sarcoma

Follicular dendritic cells (FDC) are mesenchymal-derived dendritic cells located in B-follicles where they play a pivotal role in triggering and maintaining B-cell adaptive immune response. In 1986 Dr. Juan Rosai first reported a series of neoplasms showing features of FDC and defined it as Follicular Dendritic Cell Tumor, subsequently renamed as "sarcoma" (FDCS). In its seminal and subsequent articles Rosai and colleagues highlighted the heterogeneous microscopic appearance of FDCS and its immunohistochemical and ultrastructural features.

FDCS mostly occurs in extranodal sites (79.4% of cases) and lymph nodes (15.1%); in about 7%-10% of cases it is associated with hyaline-vascular Castleman disease. Given its significant growth pattern and cytological variability, FDCS can be confused with various neoplasms and even inflammatory processes. The diagnosis requires the use of a broad spectrum of FDC markers (e.g. CD21, CD23, CD35, clusterin, CXCL13, podoplanin), particularly considering that tumor antigen-loss is frequent. The inflammatory-pseudotumor-like (IPT-like) variant of FDCS, in addition to its peculiar histopathological and clinical features, is characterized by positivity of tumor cells for Epstein-Barr virus, representing a diagnostic requisite.

No distinctive genetic and molecular anomalies have been identified in FDCS. It often carries an aberrant clonal karyotype and chromosomal structural alterations, frequently involving onco-suppressor genes. Direct or next generation sequencing showed alterations on genes belonging to the NF-κB regulatory pathway and cell-cycle regulators. In contrast to hematopoietic-derived histiocytic and dendritic cells tumors, FDCS typically lacks mutations in genes related to the MAPK pathway.

FDCS recurs locally in 28% and metastasizes in 27% of cases. Extent of the disease, surgical resectability and histopathological features are significantly associated with the outcome. IPT-like FDCS behaves as an indolent tumor, even if it often recurs locally over years.

Complete surgical excision is the gold standard of treatment. Data on targeted therapies (e.g.: tyrosine kinase inhibitors) or immune checkpoint inhibitors are very limited and responses are variable. A better understanding of the molecular drivers of this tumor may lead to potential new therapeutic strategies.

Extranodal Follicular Dendritic Cell Sarcoma-A Review: "What the Mind Does Not Know the Eye Does Not See"

Follicular dendritic cell sarcoma (FDCS) is an intermediate-grade malignancy of follicular dendritic cells, which are derived from mesenchymal stem cells. Nodal FDCS is well-recognized. However, when it occurs at an extranodal site, it may not be recognized and is often misdiagnosed. These tumors exhibit a variable spindle to epithelioid cell morphology with a lymphocytic infiltrate and a distinct immunophenotype. The World Health Organization has classified this entity under tumors of hematopoietic and lymphoid tissue, that is, histiocytic and dendritic cell neoplasms. However, its occurrence at extranodal sites and its behavior and management more closely resemble that of a soft tissue tumor. Increased awareness about the existence of FDCS at extranodal sites may aid in the reduction of diagnostic errors. We wish to draw attention to this entity by reporting our experience of 54 cases of extranodal FDCS encountered over a period of 14 years and present a review of the literature of this underrecognized entity. We also describe the ontogeny and molecular pathogenesis of this uncommon lesion.

Follicular dendritic cell sarcoma presenting as a thyroid mass: an unusual case report and literature review

Thyroid follicular dendritic cell sarcoma (FDCS) is an extremely rare malignancy that originates from follicular dendritic cells of the germinal centers and is characterized by the neoplastic proliferation of spindled to ovoid cells. As there have been only five cases reported in the literature until now, the diagnostic and therapeutic information available to clinicians regarding thyroid FDCS is fairly limited. To our knowledge, this is the first case report of thyroid FDCS without a history of Hashimoto’s thyroiditis. A 48-year-old woman was found to have a slow-growing mass in the left thyroid. After total thyroidectomy and left modified radical neck dissection, the specimen demonstrated morphologic and immunohistochemical features of FDCS. The patient had a favorable prognosis with no evidence of disease 11 months after tumor excision.

Clinical and pathologic analysis of myopericytoma in the oral and maxillofacial region

OBJECTIVE

The aim of this study was to analyze myopericytoma in the oral and maxillofacial region in terms of clinical appearance, diagnosis, treatment, and outcomes.

STUDY DESIGN

Data on 5 new patients with myopericytoma in the oral and maxillofacial region treated at our department were collected and analyzed.

RESULTS

There were 2 males and 3 females (age range 10-62 years; mean age 43.8 years). All of the 5 patients presented with masses showing benign biologic behavior. Imaging examinations with use of computed tomography or magnetic resonance imaging showed heterogeneous regions with internal contrast-enhancement or cystic change in 3 cases. All of the patients underwent surgery. Histologic examination showed a broad morphologic spectrum characterized by concentric and perivascular growth of ovoid, plump spindled, and/or round myoid tumor cells. Immunohistochemical examination showed positive staining for vimentin and smooth muscle actin, and negative for CD34 and desmin. During the follow-up period (8-56 months), there was no tumor recurrence.

CONCLUSIONS

Myopericytoma in the oral and maxillofacial region always exhibits benign biologic behavior and a heterogeneous region with internal contrast-enhancement or cystic change on imaging examinations. Surgery is the first choice of treatment and results in good clinical outcomes.

Mediastinal follicular dendritic cell sarcoma: a rare, potentially under-recognized, and often misdiagnosed disease

Background

Mediastinal follicular dendritic cell sarcoma (FDCS) is extremely rare. Due to potential under-recognization of this disease, it happens to be misdiagnosed, especially on core needle biopsy. We report 3 cases of mediastinal FDCS and provide a literature review to improve better understanding of the tumor and to reduce misdiagnosis.

Methods

Three cases of mediastinal FDCS in our clinic practice were studied, including their core needle biopsy and resected specimens, and those cases reported previously in English literature were retrieved and analyzed.

Results

The core needle biopsy of case 1 showed a tumor reminiscent of classical Hodgkin’s lymphoma (CHL), while the resected mass was finally diagnosed with FDCS combined with hyaline-vascular Castleman’s disease. Both the biopsy and resected tissue of case 2 were constitutive of the clear epithelioid cells with marked atypia. In both cases, definitive diagnoses were not made on core needle biopsy. In case 3, there were some areas morphologically similar to CHL, and some areas contained ovoid to spindle-shaped tumor cells with fascicular pattern. The analysis of 43 cases of mediastinal FDCS showed the age of patients were from 16 to 76 years old, the male to female ratio was 1.5:1, the maximal tumor diameters were 3–17 cm. 18 cases were underwent preoperative biopsy, whereas 15 (83.3%) of which were misdiagnosed initially, often as lymphoma. 32 patients had available follow-up data, the rates of recurrence, metastasis, and mortality were 12.5, 18.8 and 28.1%, respectively. Current limited data suggested no statistical differences between adverse prognosis and gender, age, tumor size, necrosis, or different therapeutics, respectively.

Conclusions

Mediastinal FDCS is a rare malignancy that has yet not been fully understood and been often misdiagnosed, particularly when making a diagnosis on core needle biopsy. Increased awareness of this enigmatic tumor is crucial to avoid diagnostic pitfalls.

Profiles of genomic alterations in primary esophageal follicular dendritic cell sarcoma: A case report

RATIONALE

Follicular dendritic cell (FDC) sarcoma is a rare tumor with FDC differentiation that typically arises within lymph nodes but can also occur extranodally. To date, the primary esophageal FDC sarcoma has not been reported in the English literature.

PATIENT CONCERNS

We described a 67-year-old female who foremostly presented with dysphagia, and the patient was readmitted due to a dry cough and pain of his right shoulder 2 years after initial treatment.

DIAGNOSES

Primary esophageal FDC sarcoma with the right superior mediastinal lymph node metastasis.

INTERVENTIONS

The esophageal tumor was removed by endoscopic submucosal dissection at the first hospitalization. At the second hospitalization 2 years after the initial visit, the tracheal stent loaded with (125) iodine radioactive seeds was placed. The profiles of genetic variations and immunotherapeutic biomarkers were also explored by next-generation sequencing protocol from the patient's blood, esophageal primary, and mediastinal metastatic tumor samples.

OUTCOMES

The patient's symptom transitorily relieved, but she gave up further treatment and died 2 months after the tracheal stent was placed. As for the genomic alterations, we found 9 gene mutations in all the samples, including checkpoint kinase 2(CHEK2), FAT atypical cadherin 1 (FAT1), tumor protein 53 (TP53), DPYD, ERBB2 interacting protein (ERBB2IP), FBXW7, KMT2D, PPP2R1A, TSC2, whereas amplification of MYC was only in the metastatic example. The analysis of clonal evolution and phylogenetic tree showed the propagation and replay of polyclonal esophageal FDC sarcoma. At the same time, the detection of biomarkers for immunotherapy revealed microsatellite stable and mismatch repair-proficient (pMMR), which predicted a relatively poor anti-programmed death (PD-1)/programmed death ligand (PD-L1) immunotherapy outcome. On the contrary, the tumor mutational burdens were 10 mutations per 1 million bases in both the primary and metastatic tumor sample, which ranked the top 23.3% in solid tumors mutational burdens database of Geneseeq and might be a good predictor of the efficacy of anti-PD-1/PD-L1 immunotherapy.

LESSONS

To the best of our knowledge, this case report announced the first case of extranodal primary esophageal FDC sarcoma in the world, and firstly revealed its unique genetic alterations profiles, which might contribute to further in-depth study of this rare disease.

[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 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.