Fibrous dysplasia is an uncommon bone disease. The diagnosis is usually not difficult, given the symptoms, radiology, and histology. The gene involved is the α subunit of the G-protein receptor. Recent innovation in molecular pathology has helped us understand the mechanism of disease pathogenesis. The treatment of fibrous dysplasia is limited to maintenance of maximum bone density. Surgical reinforcement is used to treat bowing deformities and fractures as they occur. Malignant transformation of fibrous dysplasia is rare. Currently, there is no therapy for preventing the disease from advancing or for malignant transformation.

Extraskeletal mesenchymal chondrosarcoma is a rare soft tissue sarcoma arising from soft tissues, mainly of the lower extremities, meninges, and orbits. It usually presents during the second to third decades of life, and has a slight predominance in females. Histologically, it has a typical biphasic pattern comprising small cells and islands of hyaline cartilage. It can pose a diagnostic challenge in small biopsy specimens where 1 of the 2 components can be absent. The prognosis is extremely variable; survival varies depending on the location of the tumor.

Professional medical conferences over the past five years have seen an enormous increase in the use of Twitter in real-time, also known as "live-tweeting". At the United States and Canadian Academy of Pathology (USCAP) 2015 annual meeting, 24 attendees (the authors) volunteered to participate in a live-tweet group, the #InSituPathologists. This group, along with other attendees, kept the world updated via Twitter about the happenings at the annual meeting. There were 6,524 #USCAP2015 tweets made by 662 individual Twitter users; these generated 5,869,323 unique impressions (potential tweet-views) over a 13-day time span encompassing the dates of the annual meeting. Herein we document the successful implementation of the first official USCAP annual meeting live-tweet group, including the pros/cons of live-tweeting and other experiences of the original #InSituPathologists group members. No prior peer-reviewed publications to our knowledge have described in depth the use of an organized group to "live-tweet" a pathology meeting. We believe our group to be the first of its kind in the field of pathology.

Gene fusion characterisation of rare aggressive prostate cancer variants-adenosquamous carcinoma, pleomorphic giant-cell carcinoma, and sarcomatoid carcinoma: an analysis of 19 cases Aims: To evaluate the molecular underpinnings of the rare aggressive prostate cancer variants adenosquamous carcinoma, pleomorphic giant-cell carcinoma, and sarcomatoid carcinoma. Methods and results: We retrieved 19 tumours with one or more variant(s), and performed ERG immunohistochemistry, a next-generation sequencing assay targeting recurrent gene fusions, and fluorescence insitu hybridisation (FISH) for ERG and BRAF. Divergent differentiation included: sarcomatoid carcinoma (n = 10), adenosquamous carcinoma (n = 7), and pleomorphic giant-cell carcinoma (n = 7). Five patients had more than one variant. Four had variants only in metastases. ERG rearrangement was detected in nine (47%, seven via sequencing, showing TMPRSS2-ERG fusions and one GRHL2-ERG fusion, and two via FISH, showing rearrangement via deletion). ERG was immunohistochemically positive in the adenocarcinoma in eight of nine (89%) patients, but was immunohistochemically positive in the variant in only five of nine patients (56%, typically decreased). One patient had a false-positive ERG immunohistochemical result in the sarcomatoid component despite a negative FISH result. Two (11%) harboured BRAF fusions (FAM131A-BRAF and SND1-BRAF).