A Novel EPC1::KDM2B Fusion in High-grade Endometrial Stromal Sarcoma.

The spectrum of endometrial stromal sarcoma (ESS) has expanded substantially since the publication of the most recent World Health Organisation (WHO) Classification of Female Genital Tumours and the advent of widely available genomic testing. We describe a uterine mesenchymal tumor harboring a novel EPC1::KDM2B fusion, best classified within the umbrella of high-grade endometrial stromal sarcoma (HGESS). This tumor was composed of a uniform population of spindled cells with some myxoid stroma, a mitotic rate of up to 21/10 high-power fields, and a largely pushing margin with focal vascular invasion. Immunohistochemistry showed strong and diffuse cyclin D1 positivity while CD10, WT1, DOG1, CD117, CD34, CD99, S100, MelanA, SMA, desmin, and h-caldesmon were negative. The tumor was confined to the uterus and no recurrence has been detected thus far, albeit with a short follow-up interval of 9 mo.

Parallel evolution of two distinct lymphoid proliferations in clonal haematopoiesis.

AIMS: Angioimmunoblastic T-cell lymphoma (AITL) is genetically characterized by TET2 and DNMT3A mutations occurring in haematopoietic progenitor cells, and late events (e.g. the RHOA-G17V mutation) associated with malignant transformation. As TET2/DNMT3A-mutated progenitor cells can differentiate into multilineage progenies and give rise to both AITL and myeloid neoplasms, they may also have the potential to lead to other metachronous/synchronous neoplasms. We report two cases showing parallel evolution of two distinct potentially neoplastic lymphoid proliferations from a common mutated haematopoietic progenitor cell population. METHODS AND RESULTS: Both cases presented with generalized lymphadenopathy. In case 1 (a 67-year-old female), an initial lymph node (LN) biopsy was dismissed as reactive, but a repeat biopsy showed a nodal marginal zone lymphoma (NMZL)-like proliferation with an increase in the number of T-follicular helper (TFH) cells. Immunohistochemistry, and clonality and mutational analyses by targeted sequencing of both whole tissue sections and microdissected NMZL-like lesions, demonstrated a clonal B-cell proliferation that harboured the BRAF-G469R mutation and shared TET2 and DNMT3A mutations with an underlying RHOA-G17V-mutant TFH proliferation. Review of the original LN biopsy showed histological and immunophenotypic features of AITL. In case 2 (a 66-year-old male), cytotoxic T-cell lymphoma with an increase in the number of Epstein-Barr virus-positive large B cells was diagnosed on initial biopsy. On review together with the relapsed biopsy, we identified an additional occult neoplastic TFH proliferation/smouldering AITL. Both T-cell proliferations shared TET2 and DNMT3A mutations while RHOA-G17V was confined to the smouldering AITL. CONCLUSIONS: In addition to demonstrating diagnostic challenges, these cases expand the potential of clonal haematopoiesis in the development of different lineage neoplastic proliferations.

Ovarian Clear Cell Tumors Associated With Seromucinous Borderline Tumor: A Case Series.

Ovarian seromucinous borderline tumors (SMBT) and clear cell tumors are both closely associated with endometriosis and share, in a proportion of cases, a molecular pathway involving ARID1A mutations, but they have been rarely described in association. We report a case series of 4 clear cell tumors (3 carcinomas, 1 borderline adenofibroma) coexisting in the same ovary with SMBT. In all cases, the SMBT was the predominant component and we highlight that adequate sampling of these tumors is important to detect small clear cell carcinomas, thus potentially altering the treatment and prognosis.

Biomarkers for site-specific response to neoadjuvant chemotherapy in epithelial ovarian cancer: relating MRI changes to tumour cell load and necrosis.

BACKGROUND: Diffusion-weighted magnetic resonance imaging (DW-MRI) potentially interrogates site-specific response to neoadjuvant chemotherapy (NAC) in epithelial ovarian cancer (EOC). METHODS: Participants with newly diagnosed EOC due for platinum-based chemotherapy and interval debulking surgery were recruited prospectively in a multicentre study (n = 47 participants). Apparent diffusion coefficient (ADC) and solid tumour volume (up to 10 lesions per participant) were obtained from DW-MRI before and after NAC (including double-baseline for repeatability assessment in n = 19). Anatomically matched lesions were analysed after surgical excision (65 lesions obtained from 25 participants). A trained algorithm determined tumour cell fraction, percentage tumour and percentage necrosis on histology. Whole-lesion post-NAC ADC and pre/post-NAC ADC changes were compared with histological metrics (residual tumour/necrosis) for each tumour site (ovarian, omental, peritoneal, lymph node). RESULTS: Tumour volume reduced at all sites after NAC. ADC increased between pre- and post-NAC measurements. Post-NAC ADC correlated negatively with tumour cell fraction. Pre/post-NAC changes in ADC correlated positively with percentage necrosis. Significant correlations were driven by peritoneal lesions. CONCLUSIONS: Following NAC in EOC, the ADC (measured using DW-MRI) increases differentially at disease sites despite similar tumour shrinkage, making its utility site-specific. After NAC, ADC correlates negatively with tumour cell fraction; change in ADC correlates positively with percentage necrosis. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov NCT01505829.

Ovarian Extravascular Papillary Endothelial Hyperplasia (Masson Tumor) Mimicking a Primary Gynecologic Malignancy.

Papillary endothelial hyperplasia or Masson tumor most commonly occurs within the extremities and head and neck. It is usually of intravascular type, associated with thrombus formation and organization within a preexisting vessel or vascular malformation, but rarely can be extravascular. We describe the first 2 cases of this extravascular type to occur within the ovary, one of which mimicked malignancy radiologically. This condition is thought to represent a reactive phenomenon with reparative response secondary to thrombosis although with an unclear underlying pathogenesis. The prognosis is generally good, with complete surgical resection usually representing adequate treatment.

Sarcomatous Transformation in Undifferentiated/Dedifferentiated Endometrial Carcinoma: An Underrecognized Phenomenon and Diagnostic Pitfall.

Undifferentiated/dedifferentiated carcinoma is an aggressive endometrial carcinoma which remains underrecognized but may account for up to 9% of all endometrial malignancies. We describe 3 cases in which the undifferentiated component was associated with sarcomatous differentiation, characterized by spindled cells in 2 cases and heterologous malignant cartilage in 1 case. Two of the 3 cases demonstrated mismatch repair deficiency by immunohistochemistry. This phenomenon has not previously been formally reported and increases the likelihood of misdiagnosis, especially within biopsy samples; differential diagnoses may include endometrial stromal sarcoma and grade 3 endometrioid adenocarcinoma with spindled morphology. We review the current literature and provide strategies for resolving the differential diagnoses, with a suggested panel of antibodies which includes EMA, E-cadherin, and mismatch repair proteins as approximately 50% of cases show loss of mismatch repair expression.

Follicular dendritic cell tumour/sarcoma: a commonly misdiagnosed tumour in the thorax.

AIMS: Follicular dendritic cell sarcoma is a rare tumour reported to occur occasionally in association with the hyaline-vascular type of Castleman's disease (HVCD). Most cases arise in lymph nodes, although extranodal presentation is described. METHODS AND RESULTS: Clinical, radiological and histological characteristics, including diagnosis on pre-resection material, were assessed in seven intrathoracic cases from five males and two females with a median age of 38 years. Clinical symptoms were related to mass location, six cases presenting within central and/or posterior mediastinal compartments and one within the lungs. Positron emission tomography-computed tomography demonstrated marked fluoro-deoxy-glucose avidity and the prominent vessels traversing the lesions. Four of six cases (67%) were misdiagnosed initially. HVCD was present in three cases. Two cases with high mitotic rates recurred after resection. All were positive for at least one of the follicular dendritic cell markers (CD21, CD35 and CD23). Six of seven cases (86%) show cyclin D1 expression ranging from 5% to 90%. CONCLUSIONS: Follicular dendritic cell sarcoma is often misdiagnosed on biopsy and pathologists need to be aware of the tumour to request the relevant immunohistochemistry, especially in masses presenting in the central/posterior mediastinum with high vascularity and standardized uptake values. Background HVCD appears more common than previously thought.

Pleomorphic dermal sarcoma: Clinicopathological features and outcomes from a 5-year tertiary referral centre experience.

BACKGROUND: Pleomorphic dermal sarcoma (PDS) describes rare dermal-based malignant tumours that are morphologically similar to atypical fibroxanthoma (AFX). PDS may be differentiated from AFX by the presence of one or more of the following histologic features: subcutaneous invasion, tumour necrosis, lymphovascular invasion (LVI), and/or perineural infiltration (PNI). AIMS: To further define the clinicopathological features, surgical management, and outcomes of PDS primary tumours. METHODS AND RESULTS: This study was a retrospective observational case series using a database search from 2012 to 2017. Inclusion criteria required all cases to meet the histopathologic criteria for PDS as confirmed by a specialist soft-tissue histopathologist. A total of n = 17 cases were included with a median age of 78 years (range 66-85). All tumours were located on the head and neck, with 13/17 located on the scalp. Primary treatment was with wide local excision (WLE) in all cases. Median follow-up was 48 months. Local recurrence occurred in 4/17 cases (24%) and distant metastasis in 2/17 cases (12%). CONCLUSION: PDS behaves more aggressively than atypical fibroxanthoma with which it shares a biologic continuum. The optimal surgical management approach is yet to be determined.