Histology Review PDF

Histology Review “THE PROCESS”  The Path of a Tissue Specimen Collection (OR, Clinic, Dr’s Pathology Lab Office) Accessionin Grossing Processing Embedding Microtomy...

Histology Review “THE PROCESS”  The Path of a Tissue Specimen Collection (OR, Clinic, Dr’s Pathology Lab Office) Accessionin Grossing Processing Embedding Microtomy Staining Assigning g Report Pathologist  & SPECIMEN Embedding ORIENTATION Orientation is critical Easiest is larger flat specimens Special instructions  Tubular structures – on end eg. Fallopian tube  Stratified structures – on edge eg skin  Cross section and longitudinal –Muscle or nerve Tubular structures  Embed on end  View from side  Cross section  (x-section)  Show lumen (opening)  View from above Muscle or nerve  Tissue is bisected T view  One piece placed cross-section  One placed longitudinal Striated tissue X Multiple pieces  Place in a straight line along the long axis of the mold or in orderly fashion Multiple pieces X  Tissue angle  Tissue on angle  Tissue straight X  Blade strikes small point first  Blade slams into entire side Embedding  All tissues cut better on an angle  2-4 mm of wax  Too large a mold makes cutting more difficult Several pieces of skin are received in one cassette; how should they be embedded? ON EDGE SO THAT EPIDERMIS, DERMIS & SUBCUTANEOUS LAYERS ARE ALL VISIBLE THE PIECES ARE PLACED SO THAT ALL HAVE THE EPIDERMIS FACING THE SAME DIRECTION Quality control EMBEDDING Quality control  All on same plane  Check for processing problems  Make specimens easy to find  Temperatures  Make discard careful and  Wax controlled  Cooling plate  Follow your SOPs Tiny specimens Not  Alternate tiny & large random specimens  On one plane, central Clean Scrape position forceps well well  Check instructions Open one Prevent cassette transfer only Troubleshooting Embedding Incorrect orientation  Check for special instructions BEFORE you embed  Check embedded specimens BEFORE you cut Tissue Carryover  Clean carefully between specimens  Open on cassette at a time  Alternate tiny and large specimens Embed on one level  Tamp tissue firmly and uniformly  Do not allow wax to cool early  Work quickly Tissue pieces  Number of pieces should be known  Refer to embedding log or cassette  Open cassette carefully and check top before discarding  Carefully open lens paper and keep warm while scraping Cassette not level in mold  Use forceps or spatula and tamp cassette on the mold to ensure it is seated properly Frozen sections Frozen sections OCT compound  Cryostat sections  Generally cut at -20°C  Pathologist dissects specimen  Sample placed on chuck with OCT compound  Freeze, cut  Read & report within 15-20 minutes Cryostat  Best quality sections are produced from unfixed sections  Slow freezing causes artifacts Cryostat  Freezing can be faster  Liquid nitrogen -190°C  Isopentane -150°C  Aerosol sprays -50°C  If specimens are frozen at much lower temperatures extra time must be allowed before cutting or specimen may shatter Temperature for cutting  -20°C  Warmer for water  Avoid shatter or chatter  Colder for fat  Avoid rolling up of sections Bone  Reasonable sections of bone can be obtained without decalcification if the bone is cancellous (spongy)  Useful for diagnosis of bone tumours Rate of cutting  Slow for soft  Hard and fast