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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., (© 2016 John Wiley & Sons Ltd.)

Aims: The current WHO classification of thymic epithelial neoplasms describes type A and type AB thymomas as behaving 'like benign neoplasms'. However, recent published data suggest that rare cases may show more aggressive behaviour. The aim of this study was to assess the frequency of atypical cases, and to determine whether atypia is associated with more advanced disease., Methods and Results: One hundred and twenty-one thymomas (type A, n = 68; type AB, n = 53) were retrospectively reviewed for 'atypical' features (nuclear pleomorphism, mitotic activity, and necrosis). Logistic regression was used to ascertain the association with increasing Masaoka-Koga stage. Where available, follow-up data were also reviewed. There were 72 stage I, 42 stage II, five stage III and two stage IV tumours. Only the presence of necrosis showed a significant association with increased stage in univariate and multivariate analysis. Nuclear atypia and increased mitotic activity were not associated with increasing stage of disease., Conclusions: Our data support the concept of there being more aggressive atypical variants of both type A and type AB thymoma, and suggest that the presence of necrosis could be used to predict aggressive behaviour., (© 2014 John Wiley & Sons Ltd.)

Aims: Whilst parenchymal changes in pulmonary sequestrations are well described, there are comparatively little data on associated vascular changes and their extent. The aim of this study was to retrospectively review morphological changes within sequestrations, concentrating on vascular changes and associations with clinical parameters., Methods and Results: Twenty-seven resected cases of sequestrations (intralobar n = 20, extralobar n = 7) showed a male predominance (n = 16) and an age range of 2 months-60 years (average 13 years). Plexogenic vascular changes (medial hypertrophy and intimal fibrosis) were seen in 15 of 27 cases, as well as plexiform lesions in seven cases. Patients with plexogenic changes had a higher mean age compared with those lacking vascular changes (19 versus 6 years) and were more commonly female. Respiratory tract infections were associated solely with intralobar sequestrations. No other associations between presenting symptoms and histopathological parameters were identified. Adjacent lung showed lesser plexogenic changes in six of 22 intralobar cases. There were features of type 2 congenital cystic adenomatoid lesions in 63% of cases. Dissection of the supplying systemic artery (n = 1), intralesional aspergilloma (n = 1) and coexistent lymphangiomatosis (n = 1) were also identified., Conclusions: Hypertensive vascular changes are not uncommon in both intrapulmonary and extrapulmonary sequestrations, although their relative severity seems unrelated to presenting symptoms.