Pathology for clinicians and medical students: Difference between revisions

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Sampling
 
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Important points for everyone who may send specimens to pathology:
Following are important points for everyone working clinically, and who may therefore be involved with pathology. Still, the main advice is to '''ask a pathologist''' if unsure about anything pathology-related.
 
==Notice==
Advance notice allows the pathologist to prepare accordingly.
*Provide the main condition(s) or feature(s) that you want the pathologist to '''look for''' whenever feasible.
*Whenever there is a specimen type or circumstances thereof that is presumably '''unusual''', give advance notice to the pathology department so that they can prepare accordingly.
*Advance notice also generally gives you a better reply to '''any questions''', such as before a tumor conference rather than putting the pathologist on the spot during it.
*For tumor specimens, state significant cuts or other '''iatrogenic disruptions''' in the vicinity of the tumor if they may otherwise be misinterpreted as tumor perforation.
 
==Biopsy versus aspiration==
Generally order biopsy rather than aspiration, unless you know from the pathology department that they approve of the latter for the purpose at hand. Even if there are studies of promising aspiration results for any particular purpose, such studies are generally performed by subspecialty enthusiasts in the subject at hand, and their expertise and enthusiasm is not to be compared to that of your local cytotechnicians and pathologists.
 
==Sampling==
For cystic lesions, it is generally the ''cyst lining'' that is most helpful for the pathologist to make an optimal diagnosis, especially if there are nodules on the lining. Likewise, for seemingly necrotic lesions, try to find adjacent viable material to sample.
 
==Staples==
[[File:True and reported surgical margin.jpg|thumb|220px|Margins of a [[lobectomy]]. A stapled portion is being cut off from the true bronchial margin, in order to take sections for microscopy from the underlying tissue, which therefore will be a few millimeters more proximal on the specimen than the true margin.]]
If feasible, limit the amount of staples in essential diagnostic tissue if there is a limited amount thereof (as staples need to be removed before microtomy, and the removal may tear the tissue). If multiple staples are necessary on a surgical margin (such as both ends of an intestinal segment), keep in mind that the pathologist may have to cut away the entire stapled portion before taking sections, and therefore the section for microscopy is a few millimeters more proximal on the specimen than the true margin.


==Fixation==
==Fixation==
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-->Within an hour after removal from the body,<ref>{{cite web|url=https://www.uclahealth.org/pathology/workfiles/Education/Residency%20Program/Gross%20Manual/Mastectomy%2006.03.20.pdf|title=Breast pathology grossing guidelines|website=UCLA Health|accessdate=2021-09-09}}</ref> tissue samples should generally be placed in vessels with the correct fixing solution, with a volume that allows them to lie freely in the solution.<ref name=kvast>{{cite web|url=http://www.svfp.se/foreningar/uploads/L15178/kvast/hud/Handlaggning%20av%20hudprover%20%20provtagningsanvisningar%20utskarningsprinciper%20och%20snittning%2020150325.pdf|title=Handläggning av hudprover – provtagningsanvisningar, utskärningsprinciper och snittning (Handling of skin samples - Instructions for sampling, cutting and incision|author=Katarzyna Lundmark, Krynitz, Ismini Vassilaki, Lena Mölne, Annika Ternesten Bratel|accessdate=2019-09-09|website=KVAST (Swedish Society of Pathology)}}</ref> The standard fixation fluid is generally 10% neutral buffered '''formalin''', which is roughly equivalent to 4% formaldehyde.<ref>{{cite web|url=https://microscopy.duke.edu/guides/paraformaldehyde-formaldehyde-formalin|title=Paraformaldehyde, Formadehyde and Formalin|website=Duke University|accessdate=2019-12-17}}</ref>  
-->Within an hour after removal from the body,<ref>{{cite web|url=https://www.uclahealth.org/pathology/workfiles/Education/Residency%20Program/Gross%20Manual/Mastectomy%2006.03.20.pdf|title=Breast pathology grossing guidelines|website=UCLA Health|accessdate=2021-09-09}}</ref> tissue samples should generally be placed in vessels with the correct fixing solution, with a volume that allows them to lie freely in the solution.<ref name=kvast>{{cite web|url=http://www.svfp.se/foreningar/uploads/L15178/kvast/hud/Handlaggning%20av%20hudprover%20%20provtagningsanvisningar%20utskarningsprinciper%20och%20snittning%2020150325.pdf|title=Handläggning av hudprover – provtagningsanvisningar, utskärningsprinciper och snittning (Handling of skin samples - Instructions for sampling, cutting and incision|author=Katarzyna Lundmark, Krynitz, Ismini Vassilaki, Lena Mölne, Annika Ternesten Bratel|accessdate=2019-09-09|website=KVAST (Swedish Society of Pathology)}}</ref> The standard fixation fluid is generally 10% neutral buffered '''formalin''', which is roughly equivalent to 4% formaldehyde.<ref>{{cite web|url=https://microscopy.duke.edu/guides/paraformaldehyde-formaldehyde-formalin|title=Paraformaldehyde, Formadehyde and Formalin|website=Duke University|accessdate=2019-12-17}}</ref>  


The main exception to using formalin are mainly:
{{formalin exceptions}}
*A '''[[tophus]]''' or other specimen suspicious for gout versus pseudogout should be sent in alcohol or dry, since formalin will dissolve the crystals.
{{further|Fixation}}
*[[Lymph node]]s (or other lymphoid aggregates) with a suspicion of '''lymphoma''', where samples are generally put in a special solution for flow cytometry.
*[[Products of conception]] with a need to take samples for '''genetic testing'''.


==Skin==
==Skin==
[[File:Recommended marking stitch.jpg|thumb|190px|When marking the orientation of specimens, including skins, make the knot away from the tissue so that the pathologist can remove it without potentially cutting through the tissue.]]
[[File:Recommended marking stitch.jpg|thumb|190px|When marking the orientation of specimens, including skins, make "air knots", away from the tissue so that the pathologist can conveniently remove it without potentially cutting through the tissue.]]
'''Orientation''' of skin excisions should generally be marked when there is a substantial likelihood of needing to excise further, and it is in a location where it is inconvenient to perform re-excision in all directions indiscriminately. Otherwise, skin lesions with only a mild suspicion of cancer (such as [[dark skin focalities]] in general) can usually be excised unoriented. Orientation can be made with one or two (one short and one long) sutures, designated lateral, medial etc, or o’clock positions. The direction of the margin marked by any suture should not be ambiguous (like on the border between two of them).
'''Orientation''' of skin excisions should generally be marked when there is a substantial likelihood of needing to excise further in a location where it is inconvenient to perform re-excision in all directions indiscriminately. On the other hand, skin lesions with a low to intermediate suspicion of cancer (such as [[dark skin focalities]] in general) can usually be excised unoriented with a close margin, allowing for a later extended excision in case the initial pathology shows a malignancy. Orientation can be made with one or two (one short and one long) sutures, designated lateral, medial etc, or o’clock positions. The direction of the margin marked by any suture should not be ambiguous (like on the border between two of them).
 
==Report interpretation==
*Longer discussions in the report and/or the presence of ''"Correlate clinically"'' essentially mean that the pathologist is not sure. Still, ''"Correlate clinically"'' implies that the pathologist has hope that a specific diagnosis can be reached by considering the whole clinical picture.
 
==Clinical pathology==
*When ordering vitamin D levels, generally order '''calcifediol (25-hydroxycholecalciferol)''' and/or '''25-hydroxyergocalciferol''', and '''not calcitriol''' (also known as 1,25-dihydroxycholecalciferol). The latter is reserved for specific endocrinology purposes.
*Don't order '''HbA1c''' in a patient who was '''transfused''' in the last 3 months, and consider a recent transfusion if a patient has a surprisingly normal HbA1c. In such patients, a fructosamine (glycosylated albumin) level is an alternative that is unaffected by transfusion, and reflects blood sugar control over the previous couple of weeks.<ref>{{cite web|url=https://www.clinicaladvisor.com/home/features/advisor-forum/post-transfusion-hba1c/|title=Post-transfusion HbA1c|author=Jennifer E. Frank, MD|website=ClinicalAdvisor}}</ref>
*See also: [https://www.choosingwisely.org/wp-content/uploads/2015/02/ASCP-Choosing-Wisely-List.pdf Thirty five major recommendations on test ordering (Choosing Wisely initiative 2020)]
*When ordering '''platelets''' or '''red blood cells''', the patient will generally be transfused faster if you abide by the recommended dosage (generally one dose at a time, followed by a blood test to see the effect), rather than ordering excess units. With excess units ordered, even the first unit might be held up until blood bank staff has looked into the case in order to approve or reject the additional units.
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