5.5 Biopsy considerations and the biopsy report

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Clinical practice guidelines for keratinocyte cancer > 5.5 Biopsy considerations and the biopsy report


Background

Both the clinician and the anatomical pathologist have responsibilities in enhancing the value of the biopsy report.

Clinician’s responsibilities

The best approach to biopsy is complete excision of the lesion (if appropriate) as this facilitates study of the architecture and cytological appearances of the tumour, assessment of its extent, and an assessment of adequacy of excision.

If complete excision is not considered appropriate, small representatives samples can be useful, such as those obtained by one or more punch biopsies, shave biopsy or curettage, taking into account the size and depth of the lesion under consideration. With curettage, the risk of disruption of the architecture should be kept in mind.

Samples from different anatomical sites should be carefully labelled and placed in separate specimen containers. Suture markers and appropriate accompanying diagrams are important guides for the pathologist, particularly in the assessment of completeness of excision. It is also helpful to indicate the site of any extension of the tumour to the specimen edges. By convention, the suture will be denoted as 12 o’clock when not otherwise indicated.

Diagnoses under consideration should be indicated, as this information can prompt the anatomical pathologist to take special measures, such as examining extra sections or using special stains to assess these possibilities, particularly with lesions on the face.

The following clinical information should be provided on request form:

  • patient identification (full name, age and sex)
  • site of biopsy
  • description and duration of the lesion and of any associated symptoms
  • clinical diagnosis or differential diagnoses
  • history of previous treatment of lesion
  • history of previous biopsies
  • history of other skin tumours
  • presence of scars, burns or ulceration
  • diagram of excision specimen with markers for orientation.

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Pathologist’s responsibilities

Specimen sampling

The pathologist should ensure that there is optimal sampling of the specimen. Particularly for smaller specimens, the entire tissue should be sliced with multiple sections embedded for sectioning.

For skin specimens, significant (≥20%) shrinkage may occur with formalin fixation,[1] leading to disparity between clinical measurements of the lesion and excision margins and corresponding measurements made on prepared sections. Shrinkage is less with specimens from older individuals and with specimens from the head and neck. This is thought to reflect loss of elastic strength in photo-damaged skin.

Components of the pathology report

The pathologist’s report should contain:

  • the clinical notes
  • the macroscopic description
  • the microscopic findings
  • margins of excision
  • prognostic factors.


Reporting of excision margins

Excision margins should be measured if necessary. This is particularly important with narrowly excised lesions.

The validation of tumour clearance margins is partially dependent on the number of tissue blocks and sections examined when the conventional technique of bread-loafing the excisional specimen is used. Using this technique, infiltrating, morphoeic and micronodular subtypes of basal carcinoma may occasionally have undetected extensions to surgical margins. Mohs micrographic surgery using frozen sections examines excision margins more comprehensively, leading to a lower recurrence rate (see: Surgical treatment), but the technique is not practical for use in all skin specimens submitted for histopathology[2]

It is helpful to measure the thickness of deeply extending tumours in the dermis, as this information may help the clinician in planning subsequent treatment. For complex specimens, an attached diagram indicating the method of sampling and the relationship of the tumour to lines of excision can be helpful to the clinician.

Prognostic information in the pathology report

The pathology report should include a synoptic checklist of information useful for prognosis. These include:

  • tumour type
  • degree of differentiation or subtype of the tumour
  • tumour thickness in the dermis
  • perineural, vascular or lymphatic spread.

Prognostically significant terms in pathology reports should be consistent and unambiguous (Table 3).


Table 3. Terms in the pathology report that have prognostic significance

Term Explanation and notes
Poorly differentiated Refers to tumours in which the products of differentiation, such as keratin or desmostromal attachments, are poorly expressed.

Immunohistochemistry techniques for keratin subsets are often used to identify such tumours.

Basosquamousshowing evidence of squamatisation (descriptor applicable to basaloid tumours and indicating aggressive subtype) carcinoma, metatypicalshowing evidence of squamatisation (descriptor applicable to basaloid tumours and indicating aggressive subtype) carcinoma Uncommonly, tumours may show histological features intermediate between BCC and cSCC. These generally behave more like cSCC and, in practice, they should be considered to be forms of cSCC.

Pathologists should generally avoid using these terms because they are potentially confusing.

Desmoplasiagrowth pattern characterised by sclerotic and extensive fibrous stroma Prominent fibrous or sclerotic stromal changes associated with tumours, especially BCC, and less commonly cSCC. Clinically, such tumours may be mistaken for scars. They are ill defined and prone to recurrence.

Pathologists should generally avoid this term and instead use a term like ‘fibrosing’, to avoid confusion with the desmoplastic melanoma sub-type.

Large tumour Tumour size greater than 2cm in diameter is associated with increased risk of tumour recurrence, particularly for cSCCs. For cSCCs of diameter more than 2cm, the risk of recurrence is two times higher (15.2% versus 7.4%) and the risk of metastasis is three times higher (30.3% versus 9.1%) than for small cSCCs.[3]
Perineural involvement Neural involvement by tumours takes the form of perineural spread, which may extend into the deep tissue. This is particularly important in facial lesions.

Perineural involvement near the surgical margins is an indication that further measures are required for tumour clearance.

Dermal lymphatic spread Dermal lymphatic spread in satellite nodules may be seen as separate from the primary lesion and represents a poor prognostic sign.
BCC: basal cell carcinoma; cSCC: cutaneous squamous cell carcinoma

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Other information in the pathology report

The pathology report may refer to previous biopsies.

On occasions, appended comments and references can be useful to assist the clinician with interpretation. The following are examples of appropriate comments to include in the pathology report:

  • Actinic keratosis may be regarded as the earliest stage of cutaneous squamous cell carcinoma (cSCC), but with a low risk of progression.
  • The finding of cSCC in situ does not have the same prognostic significance as invasive cSCC, and may not have the same implications for level of treatment.
  • The follicular involvement noted (in some cases of Bowen’s diseasecSCC in situ (also known as intra-epidermal SCC)) suggests that recurrence may not be prevented with some forms of superficial therapy.

Communication between the clinician and the pathologist

The clinical value of the biopsy report will often be enhanced by communication between the clinician and the pathologist. This may entail obtaining additional clinical information, discussing technical aspects of the biopsy, interpreting the report and planning for future management.

If there is uncertainty in the pathology report, the clinician, in consultation with the pathologist, should seek further evaluations of the slides and/or specimen.

Practice Points

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PP 5.5.1. Excision biopsy should be performed when appropriate. If complete excision is not possible, punch biopsies, shave biopsy or curettage can be considered, as appropriate to the size and depth of the lesion.

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PP 5.5.2. A suture should be placed in the specimen and a diagram should be provided to enable the pathologist to orient the specimen within the anatomical site and/or lesion.

Key point(s)

Samples from different anatomical sites should be carefully labelled and placed in separate specimen containers.

The pathology request should include:

  • the patient’s full name, age and sex
  • site of biopsy
  • a description and duration of the lesion and any associated symptoms
  • relevant clinical history (e.g. other skin tumours, the presence of scars, burns or ulceration)
  • previous biopsies and treatment
  • diagnoses under consideration.

The pathologist’s report should contain:

  • the clinical notes
  • the macroscopic description
  • the microscopic findings
  • margins of excision
  • a summary of prognostic factors including tumour type, tumour subtype or degree of differentiation, thickness in the dermis, perineural invasion, and vascular or lymphatic spread.

If there is uncertainty in the pathology report, the clinician, in consultation with the pathologist, should seek further evaluations of the slides and/or specimen.


References

  1. Gregory N, Mulvaney M, Pattison T, Hill J, Carlson JA, Goncharuk V. Shrinkage of skin excision specimens and downcoding. Arch Dermatol 2003 Apr;139(4):542-3 Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/12707111.
  2. Nelson BR, Railan D, Cohen S. Mohs' micrographic surgery for nonmelanoma skin cancers. Clin Plast Surg 1997 Oct;24(4):705-18 Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/9342512.

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