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The diagnosis of central nervous system tumours has been transformed in recent years from a microscopic morphology-based process to one dominated by the identification of somatic genetic alterations in tumour cells. This switch requires implementing radically different methods, for which appropriate training and financial resources must be allocated. The Canadian Association of Neuropathologists (CANP) has followed a process based on the scientific literature and consensus to develop recommendations for molecular testing of tumours of the brain and spinal cord, aiming to balance the need for treatment-determinant accurate diagnosis and the current limitations inherent in the transition to a new paradigm. The Professional Affairs Committee was charged with this task. A draft was discussed during the CANP general assembly, along with presentations from groups who had implemented molecular technologies, as well as others who relied on external laboratories. The Professional Affairs Committee summarised the consensus and submitted their recommendation to the CANP's Executive Committee. A final report was posted on the CANP website for a month to allow all members to comment. The recommendations below apply to intrinsic tumours of the central nervous system and do not include metastatic disease or tumours impinging upon the nervous system from outside. These recommendations should be considered clinically relevant, as the results have direct consequences on the patient's treatment, either through the use of targeted therapies or the trial-proven best application of radiation and/or chemotherapy.

Background: Fibro-adipogenic progenitors (FAP) are muscle resident mesenchymal stem cells pivotal for regulation of myofiber repair. Experimental results show in addition involvement in a range of other pathological conditions and potential for pharmacological intervention. FAP histopathology in human muscle biopsies is largely unknown, but has potential to inform translational research. Methods: CD10+ FAPs in 32 archival muscle biopsies from 8 groups (normal, dermatomyositis, inclusion body myositis (IBM), anti-synthetase syndrome, immune-mediated necrotizing myopathy (IMNM), denervation, type 2 atrophy, rhabdomyolysis) were visualized by CD10 immunohistochemistry and their histology compared. Groups are compared by semi-quantitative scoring. Results: Histological activation of endomysial CD10+ FAPs includes prominent expansion of a network of cell processes surrounding muscle fibers, as well as endomysial cell clusters evidencing proliferation. Prominence of periarteriolar processes is a notable feature in some pathologies. FAP activation is often associated with fiber degeneration/regeneration, foci of inflammation, and denervation in keeping with experimental results. Type 2 atrophy shows no evidence of FAP activation. Dermatomyositis and anti-synthetase syndrome associated myositis demonstrate diffuse activation. Conclusion: Assessment of CD10+ FAP activation is routinely possible using CD10 immunohistochemistry and demonstrates several patterns in keeping with preclinical results. Prominent expansion of FAP processes surrounding myofibers suggests enhanced interaction between myofiber/basement membranes and FAPs during activation. The presence of diffuse FAP activation in dermatomyositis biopsies unrelated to fiber repair raises the possibility of FAP activation as part of the autoimmune process. Future diagnostic applications, clinical significance and therapeutic potential remain to be elucidated.