Pathology for clinicians and medical students

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Revision as of 07:31, 28 October 2022 by Mikael Häggström (talk | contribs) (→‎Skin: conveniently)
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Author: Mikael Häggström [note 1]
Important points for everyone who may send specimens to pathology:

Advance notice

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.

Staples

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 possible, limit the amount of staples in essential diagnostic tissue if there is a limited amount thereof (as staples need to be removed for 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

Within an hour after removal from the body,[1] 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.[2] The standard fixation fluid is generally 10% neutral buffered formalin, which is roughly equivalent to 4% formaldehyde.[3]

The main exception to using formalin are mainly: edit

  • Intraoperative consultation. If a specimen has several parts, and you only want intraoperative consultations on some of them, hold the rest back to avoid potential delays. For all fresh specimens, communicate clearly (such as on a requisition form with the specimen) whether intraoperative consultation is requested or not.
  • A tophus or other specimen suspicious for gout versus pseudogout should be sent in alcohol or dry, since formalin will dissolve the crystals.
  • Lymph nodes (or other lymphoid aggregates) with a suspicion of lymphoma, where samples are generally put in a special solution for flow cytometry.
  • Products of conception in cases where there is a need to take samples for genetic testing.
  • Cytology specimens, which are preferably sent fresh (such as in red top tubes) to be processed within a few hours. If processing may be after a few hours, put tubes on ice, or add 50% alcohol.[4]

If you don't know, and if you cannot soon get in touch with anyone who can guide you, specimens can generally be stored in a fridge in the meantime, even overnight if it is late (but make sure to follow-up as soon as possible in the morning). Until then, don't put the specimen in formalin and don't freeze the specimen. Further information: Fixation

Skin

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 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.

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.[5]

Notes

  1. For a full list of contributors, see article history. Creators of images are attributed at the image description pages, seen by clicking on the images. See Patholines:Authorship for details.

Main page

References

  1. . Breast pathology grossing guidelines. UCLA Health. Retrieved on 2021-09-09.
  2. Katarzyna Lundmark, Krynitz, Ismini Vassilaki, Lena Mölne, Annika Ternesten Bratel. Handläggning av hudprover – provtagningsanvisningar, utskärningsprinciper och snittning (Handling of skin samples - Instructions for sampling, cutting and incision. KVAST (Swedish Society of Pathology). Retrieved on 2019-09-09.
  3. . Paraformaldehyde, Formadehyde and Formalin. Duke University. Retrieved on 2019-12-17.
  4. . How to send fluid and make good cytology slides. Tufts University.
  5. Jennifer E. Frank, MD. Post-transfusion HbA1c. ClinicalAdvisor.

Image sources