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Exocytosis in a Skeletal Muscle Biopsy

Exocytosis, Neuro Notes, arkana laboratories, muscle biopsy
This electron micrograph of two adjacent skeletal muscle cells demonstrates simultaneous exocytosis.  Exocytosis in this case shows extravasation of lysosomes from inside the muscle fiber's cytoplasm by fusion with the plasma membrane (aka sarcolemma) and being expelled into the extracellular space beneath the basement membrane (aka basal lamina).  Exocytosis is one mechanism for remodeling of the sarcolemmal membrane that takes place under physiological and pathophysiological conditions, including trafficking of transmembrane machinery, muscle fiber regeneration following injury, and denervation.  Much has been written on this topic, but the details at the molecular level are still being elucidated.  (Electron micrograph original magnification:...

Sarcoidosis in a Skeletal Muscle Biopsy

sarcoidosis, neuro notes, arkana laboratories
These images show skeletal muscle from the thigh of an African-American patient with muscle weakness and elevated CPK levels.  Occasional well-formed non-caseating granulomota with mild surrounding chronic lymphoid inflammation are present. These morphologic findings are consistent with the presence of granulomatous myositis, and compatible with sarcoidosis: clinical correlation is required. (hematoxylin and eosin stained frozen section 100x and 200x magnification).    

Lipid Storage Myopathy

Lipid Storage Myopathy, Arkana Laboratories, neuro notes, neuropathology, molecular pathology
This adult patient presented with progressive muscle weakness, elevated CK, and was admitted for rhabdomyolysis. Skeletal muscle biopsy was performed of the quadriceps (Image 1, Hematoxylin and eosin-stained frozen section, original magnification x200). What is your diagnosis?   Answer:  Lipid Storage Myopathy Optically clear spaces within muscle may be due to lipid or glycogen.  Optically clear spaces may also occur due to ice crystal formation when muscle biopsy tissue is frozen too slowly or is edematous (so-called "freezing artifact").  In this case, the vacuoles are due to abnormal accumulation of lipid (i.e. Lipid Storage Myopathy), see Image 2.  (Figure 2:  Oil-red-O...

Diffuse Astrocytoma IDH-Mutant

brain biopsy, Diffuse Astrocytoma IDH-Mutant, neuro notes, neuropathology
The field of neuropathology is currently in a state of exponential growth and increased understanding of the pathogenesis of brain tumors, which has been heralded in the literature by the Consortium to Inform Molecular and Practical Approaches to CNS Tumor Taxonomy, Not Official WHO (cIMPACT-NOW) working groups.  For example, in this case of a diffusely infiltrating glioma in an adult patient, MRI neuroimaging shows mild T2 hyperintensity and increased FLAIR signal in the left parietal-occipital lobes with extension across the midline at the genu of the corpus callosum (Figures 1 and 2, respectively).  Stereotactic brain biopsy with neuronavigation yields hypercellular...

Pituitary Gland

pituitary adenoma, pituitary gland tumor, arkana laboratories, neuro notes, neuropathology
Using the Wilder's reticulin special silver stains, can you spot which image shows pathologic change in this endoscopic transnasal transsphenoidal resection of a pituitary gland tumor?   Answer:  The first image is from normal adenohypophyseal (anterior) lobe pituitary gland tissue, while the second image is from a pituitary adenoma (SF1+ gonadotroph adenoma in this case, stains not shown).  Reticulin staining is very useful in identifying destruction of the normal reticulin network characteristic of the acinar architecture observed in anterior lobe tissue of the pituitary gland.

Perifascicular Atrophy in Dermatomyositis

Perifascicular Atrophy, neuro notes, Arkana Laboratories, muscle biopsy
What histologic finding is observed in this case?     Answer:  Perifascicular Atrophy in Dermatomyositis   This case shows an acquired inflammatory myopathy with well-developed perifascicular atrophy.  Generally speaking, acquired inflammatory myopathies may be morphologically grouped into three categories: Polymyositis, Dermatomyositis, and Inclusion Body Myositis.  The classification of acquired inflammatory myopathies has undergone recent refinement, and additional entities show characteristic morphologic and clinical features (see Pestronk reference).  In the realm of acquired inflammatory myopathies, perifascicular atrophy is characteristic of dermatomyositis. The finding of skin rash in a characteristic distribution on physical exam is helpful, but is not always present (i.e. involvement...