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Dermatopathology reports about basal cell carcinoma margins cannot be marginal

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By Warren R. Heymann, MD
July 30, 2018

Significant portions of residual basal cell carcinoma can be missed in the dermis (A) or subcutaneous fat (B). Small nests are highly unlikely to be detected by serial cross-sections (C). The line from the transparency is visible in A and B but is not in sharp focus because it lies in a different plane from the specimen. (A-C, Toluidine blue stain; original magnifications: A, ×40; B, ×40; C, ×100.)
Credit: JAAD

“The tumor appears to be completely excised on the sections studied”

I have written that comment thousands of times on my dermatopathology reports for biopsies of basal cell carcinomas (BCCs). When I read the article by Willardson et al (1) regarding the predictive value of negative margins of BCCs, I gave pause. Do the clinicians understand what I mean by the qualifier “on the sections studied?”
It is self-evident (to me) that skin biopsies only reveal up to 2% of a specimen, and unless marginal assessment akin to the Mohs technique is performed, clinicians cannot be confident that a lesion has been excised. (Even Mohs surgery is not perfect.) What I mean by “on the sections studied” is predicated on the knowledge that since so little of the specimen is being evaluated, I cannot be sure about the margins if other sections were obtained. What concerned me is that perhaps my comment is being misinterpreted as the lesion is definitely excised and that no further treatment is necessary.

Certainly, there is no question that when a comment is rendered stating “the lesion extends to the margins of the specimen”, more work needs to be done. Additionally, there is no quandary about reporting margins when the lesion has been submitted as an excision of a basal cell carcinoma (by standard excision, shave excision, or saucerization).

Willardson et al collected BCC biopsies with negative margin readings that had subsequent excisions to determine the negative predictive value (NPV). For excisions read as negative for residual BCC, the excision blocks were sectioned at 150-μm intervals until exhausted. They collected 143 cases that met criteria; 34 (24%) were found to contain residual BCC in the corresponding excision leading to a NPV of 76%; in 31 of 34 (91%) of these cases, the residual histologic subtype was superficial. The authors concluded that negative margins in a BCC biopsy are a poor predictor of residual disease in the patient. They recommended that clinicians treat these lesions, and that pathologists who comment on margin status of BCC biopsies consider adding a caveat to reflect these findings, noting that judgment of definitive treatment should not be based solely on the biopsy.
Similar findings were observed in the study of Schnelbelen et al. They collected shave biopsies of squamous cell carcinomas (SCCs) and BCCs that appeared to have uninvolved margins on routine sign out. They then obtained deeper levels on corresponding tissue blocks until blocks were exhausted and examined them for tumor at biopsy margins. Forty-seven consecutive cases were collected, including 20 SCCs (43%) and 27 BCCs (57%). Eleven of 47 cases (23%) with negative margins at initial diagnosis demonstrated positive margins upon deeper-level examination. Margins of 8 of 27 BCCs and 3 of 20 squamous cell carcinomas were erroneously classified as “negative” on routine examination. The authors do not advocate for the exhaustion of all paraffin tissue blocks on shave biopsies of cutaneous carcinomas because “that exercise would be impractical”. The authors no longer report margin status routinely. For small tumors on which shave biopsies are performed, with curative intent, they perform deeper sections if margin assessment is requested by the clinician. (2)

BCCs occur in an estimated 2 million Americans annually. The lifetime risk in the U.S. is estimated to be at least 20% and greater than 30% for Caucasians; this could be greater since these estimates are based on data from almost twenty years ago. The BCC cost burden continues to increase with rising incidence. (3)
No clinician wants to leave residual tumor behind, and 25% is a significant number. Alternatively, approximately 75% of BCCs were cleared by the biopsy alone. Periodically, I will simultaneously perform a shave biopsy immediately followed by destruction (usually electrodesiccation and curettage), especially for small lesions on elderly patients, so they need not make a follow-up visit. Of course, reimbursement will only be for the biopsy (unless you wait for the report, and just charge for destruction, if positive). Under such circumstances, whether or not the lesion goes to the margin is moot. If that approach was taken in the majority of cases, imagine the cost savings. (A busy clinician would not be losing very much – instead of scheduling a follow-up for local destruction, another patient will be seen instead).

Clinicians are least satisfied with pathology laboratories that have poor communication of significantly abnormal results. (4) I will call the clinician directly when there is a potentially urgent diagnosis — melanoma, cutaneous metastasis, etc. — but not for a superficial BCC extending to the margin. Regardless, we have to avoid the Cool Hand Luke scenario (“What we have here is a failure to communicate”) even in our written reports. Dermatologists and dermatopathologists need to understand each other. After reading Willardson’s article, I wrote to my colleagues to make sure that they precisely understood what I mean by “the tumor appears to be completely excised on the sections studied” when they read my report – that alone will optimize patient outcomes. Communication is also a two-way street. I would find it most helpful to know the intent of the biopsy. If it is “rule out BCC,” I have to assume it is for diagnostic reasons only. Alternatively, if the specimen was submitted as “BCC — small lesion — margins clear?” changes the dynamic. When it comes margins of skin cancer we have to make sure there is no margin for error in the interpretation of our reports.

Point to Remember: On routine biopsies of basal cell carcinomas, you cannot rely on comments about the involvement of the margin, or lack thereof. Make sure you and your dermatopathologist understand each other for optimal patient care.

1. Willardson HB, et al. Predictive value of basal cell carcinoma biopsies with negative margin: A retrospective cohort study. J Am Acad Dermatol 2018; 79: 42-6.
2. Schnelbelen AM, et al. Margin status in shave biopsies of nonmelanoma skin cancers: Is it worth reporting? Arch Pathol Lab Med 2016; 140: 678-81.
3. Cameron MC, et al. Basal cell carcinoma. Part I. J Am Acad Dermatol 2018; May 18 [Epub ahead of print].
4. Korbi JD et al. “Why don’t they ever call? Expectations of clinicians and pathologists regarding the communication of critical diagnoses in dermatopathology. Pathology 2018; 50: 305-12.

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