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    Thymus and mediastinal masses

    Background

    Thymectomy may be undertaken for the removal of benign and malignant tumours or for the treatment of myasthenia gravis.1-5


    Record the patient identifying information and any clinical information supplied together with the specimen description as designated on the container. See overview page for more detail on identification principles.

    The International Thymic Malignancy Interest Group (ITMIG) recommends detailed operative notes that include:4

    • Extent of resection performed (e.g. complete thymectomy)
    • Presence and location of any residual tumour in the patient
    • Presence and locations of any adhesions that were not suspicious for involvement
    • Any additional structures and/or organs removed (e.g. mediastinal pleura, pericardium, phrenic nerve, innominate vein and/or lung)
    • Any sites of intraoperative concern; method of marking in specimen and in the patient
    • Lymph nodes explored and extent of assessment (e.g. sampling or complete dissection)
    • Whether pleural and pericardial spaces were able to be assessed for metastases
    • No
      • Non-routine fixation (not formalin), describe.
    • Yes
      • Special studies required, describe.
      • Ensure samples are taken prior to fixation.
    • Not performed
    • Performed, describe type and result
      • Frozen section
      • Imprints
      • Other, describe

    See general information for more detail on specimen handling procedures.

    Inspect the specimen and dictate a macroscopic description.


    External Inspection

    Orientate and identify the anatomical features of the specimen.

    Record additional orientation or designation provided by operating clinician:

    • Absent
    • Present
      • Method of designation (e.g. suture, incision)
      • Featured denoted

    Anterior, posterior, and right and left aspects should be identified by the surgeon.2

    A standard approach to surgical orientation and marking is recommended by the International Thymic Malignancy Interest Group.

    Indicate with sutures (through loose tissue and into substantial deeper tissue to prevent disruption):

    • Any margin(s) of concern
    • Surface adjacent to the pericardium and innominate vein (or the structures if resected)
    • Surface adjacent to the vena cava (larger tumours, if nearby)
    • Right and left pleural surfaces (larger tumours if resected)

    The specimen should be orientated by the surgeon and orientation communicated clearly to the Pathologist. The ITMIG recommends the following methods:4

    • Mounting the unfurled specimen on a board
    • A diagram of the specimen with adjacent structures and marking sutures
    • A digital photograph of the mounted specimen

    Photograph the intact specimen.

    Describe the following features of the specimen:

    Procedure

    Record as stated by the clinician.

    • Biopsy, refer to instructions for respiratory small biopsies
    • Thymectomy
    • Partial thymectomy
    • Mediastinal mass resection (other than thymus)
    • Other, describe

    Anatomical components included (more than one may apply) and specimen dimensions (mm)

    Record the components present and measure as applicable.

    • Total specimen, in three dimensions2,3
    • Thymus
    • Other, describe
    • Separate nodules, specify2
      • Number
      • Sites
      • Size of each in three dimensions

    Weight (g)

    • Record the weight of the total specimen.3,5

    Specimen integrity3

    • Intact
    • Disrupted, describe surface and area involved
    • Fragmented

    Dissection

    Paint the specimen with coloured inks indicating any orientated margins or specific landmarks (it may not be necessary to paint the entire specimen).

    Serially section the specimen from superior to inferior at 3-4mm intervals.2

    After opening, the specimen may require longer fixation in larger quantity of formalin.


    Internal Inspection

    Describe the internal or cut surface appearance including the following items:

    Tumour

    • Absent
    • Present
      • Number; if more than one tumour, designate and describe each tumour separately

    If only one tumour nodule is identified, it is assumed to represent the primary tumour. If >1 separate tumour nodules are identified, the primary tumour should be separately designated from other tumour nodules 2, 3, 4 etc.

    Tumour size (mm)2

    • Maximum dimension
    • Other dimensions

    Tumour location2

    • Thymic
    • Ectopic, specify site if known

    Extrathymic tumour spread (if applicable)

    • Macroscopic extension of tumour into mediastinal fat2
    • Pulmonary parenchyma, specify lobe(s)
    • Pleura, specify location
    • Pericardium
    • Diaphragm
    • Other, describe

    Distance of tumour to margins (mm)

    • Distance of tumour to closest surgical margin(s)3
    • Specify margin

    Distance between tumour nodules (mm) -if applicable

    If more than one tumour nodule, record:
    • Distance of other tumour nodules from the primary (largest nodule)

    Non-lesional tissue appearance5

    • Fatty
    • Biopsy related changes
    • Cystic
    • Thymic hyperplasia

    Retrieved from resection specimen

    • Describe site(s)
    • Number retrieved

    Separately submitted

    • For each specimen container, record specimen number and designation
    • Collective size of tissue in three dimensions (mm)
    • Number of grossly identified lymph nodes submitted
    • Maximum diameter of each (mm)

    Processing

    Dissect the specimen further and submit sections for processing according to the diagram provided.

    Submit all sections in sequential order.2

    Submit representative sections, at least one block per 10mm of tumour2 or lesion demonstrating:

    • Surgical margins
    • Relationship with thymic capsule and extrathymic tissue
    • Cyst walls, if applicable
    • At least one block of non-lesional thymus

    Submit all lymph nodes and identify the site of each.

    Record details of each cassette.

    An illustrated block key similar to those provided below may be useful.

    Block allocation keys

    Cassette id
    Site
    No. of pieces
    A+
    All sections
     
    Cassette id
    Site
    No. of pieces
    A
    Surgical margins
     
    B-D
    Tumour demonstrating relationship with thymic capsule and extrathymic tissue
     
    E
    Cyst walls, if applicable
     
    F
    Non-lesional tissue
     
    G+
    Lymph nodes if applicable
     

     

    Acknowledgements

    Dr Jenny Ma Wyatt or her contribution in reviewing and editing this protocol.


    References

    1. Lester SC. Manual of Surgical Pathology, Saunders Elsevier, Philadelphia, 2010.
    2. Nicholson AG, Kerr K, Gosney J and Cane P. Dataset for the histological reporting of thymic epithelial tumours, The Royal College of Pathologists, London, 2013.
    3. College of American Pathologists. Cancer Protocols. (Accessed 21 Jun 2013).
    4. Detterbeck FC, Moran C, Huang J, Suster S, Walsh G, Kaiser L, et al. Which Way is Up? Policies and Procedures for Surgeons and Pathologists Regarding Resection Specimens of Thymic Malignancy. Journal of Thoracic Oncology. 2011;6(7):S1730-S8.
    5. Nicholson AG. Tissue pathway for non-neoplastic thoracic pathology. London: The Royal College of Pathologists, 2013.

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      Thymus 1

      Thymus

      Thymus 2

      Thymus dissected

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      27-Mar-2019
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