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Moon DJ, Higgins S, Feinstein S, Ahadiat O, Sutton A, Wysong A. Variance of Basal Cell Carcinoma Subtype Reporting by Practice Setting. JAMA Dermatol. 2019;155(7):854–856. doi:10.1001/jamadermatol.2019.0066
Aggressive subtypes of basal cell carcinoma (BCC) have been shown to require more Mohs surgery stages, to have a higher incidence of positive margins after excision and increased subclinical extension on histologic analysis, and to have greater rates of recurrence.1-3 However, in practice, reporting of BCC subtypes may vary. The clinician’s ability to provide appropriate management recommendations may be misguided if BCC histologic subtypes are not specified on the biopsy pathology report. In this study, we examined differences in reporting of BCC subtypes on results of biopsy in various practice settings and discuss the important clinical implications.
We retrospectively studied 928 biopsy-proved BCCs treated with Mohs micrographic surgery by a single Mohs surgeon (A.W.) at an academic tertiary institution from January 1, 2015, to December 31, 2017. This study was deemed exempt by the institutional review board of Keck School of Medicine of the University of Southern California, Los Angeles, and informed participant consent was waived. Data were collected on patient characteristics, histologic subtype on results of biopsy and Mohs micrographic surgery, type of institution from which the biopsy pathology report originated, and the number of Mohs stages. Institutions were categorized as academic if they have medical schools, other teaching if they support graduate medical education, and nonteaching if neither. Tumors were classified as aggressive if they contained an infiltrating, micronodular, morpheaform, or basosquamous subtype. Fisher exact tests and unpaired, 2-tailed t tests were conducted using Stata, version 15 (StataCorp), with a 2-sided P < .05 indicating statistical significance.
Subtypes of BCC were not specified in 94 of the 928 biopsy pathology reports (10.1%). As shown in Table 1, subtype reporting did not vary by race/ethnicity or insurance but was significantly associated with the practice setting, among which 27 of 429 pathology reports (6.2%) from academic institutions, 14 of 59 reports (23.7%) from other teaching institutions, and 50 of 138 reports (36.2%) from nonteaching institutions did not provide a histologic subtype.
Among 94 BCCs with no initial subtype, 42 (44.7%) were found to have aggressive subtypes during Mohs micrographic surgery, which included infiltrating (22 BCCs [23.4%]), micronodular (21 [22.3%]), morpheaform (4 [4.3%]), and basosquamous (2 [2.1%]) (Table 2). Four of these cases showed invasion beyond the subcutaneous layer, 1 of which had perineural invasion. To account for discordances in BCC subtypes between biopsy and Mohs frozen sections, as reported in the literature,2,5,6 we compared BCCs lacking subtypes with BCCs classified as nonaggressive on the biopsy report and found that intraoperative detection of unsuspected aggressive subtypes was still significantly more frequent in BCCs lacking subtypes on the initial biopsy report (odds ratio, 1.92; 95% CI, 1.03-3.57; P = .04). Furthermore, BCCs lacking subtypes required significantly more Mohs layers for clearance compared with BCCs reported as nonaggressive on results of the initial biopsy (mean [SD], 2.03 [1.20]) compared with mean number for BCCs reported as nonaggressive (mean [SD] 1.75 [0.84]); 95% CI for difference in means, 0.08-0.48; P = .005) but not compared with BCCs reported as aggressive on the biopsy results (mean number of Mohs layers, 1.98; 95% CI, −0.32 to 0.21; P = .71). This finding suggests that BCCs should not be assumed to be nonaggressive if no subtype is provided. Some pathology reports specified that subtypes were unable to be given owing to limited tissue availability, which may occur with small biopsies, and 1 reported an unclear differential, but most reports did not provide explanations.
Our study found significantly different pathology reporting patterns for BCC on biopsy results across practice settings, suggesting a potential gap in delivery of care. This retrospective study may have limitations in its generalizability, as findings were based on BCCs treated at a single tertiary academic center, which may potentially result in a bias toward more aggressive BCCs compared to those treated at community hospitals or private clinics. Overall, BCCs without subtypes were found to require a significantly higher number of Mohs layers to achieve clearance, and 44.7% had aggressive subtypes identified on definitive Mohs excision. Per the 2012 appropriate use criteria for Mohs micrographic surgery from the American Academy of Dermatology, American College of Mohs Surgery, American Society for Dermatologic Surgery Association, and American Society for Mohs Surgery,4 the appropriateness of Mohs micrographic surgery varies between aggressive and nonaggressive subtypes, depending on the size and location of the lesion. A lack of subtyping may place the patient at risk for inadequate or inappropriate therapy. Therefore, we highlight the importance of providing BCC subtypes and seek to increase clinician awareness of the potential for aggressive characteristics seen in BCCs without reported subtypes.
Accepted for Publication: December 28, 2018.
Corresponding Author: Ashley Wysong, MD, MS, Department of Dermatology, University of Nebraska Medical Center, 985645 Nebraska Medical Center, Omaha, NE 68198-5645 (firstname.lastname@example.org).
Published Online: April 17, 2019. doi:10.1001/jamadermatol.2019.0066
Author Contributions: Ms Moon and Dr Wysong had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.
Concept and design: Moon, Higgins, Ahadiat, Sutton, Wysong.
Acquisition, analysis, or interpretation of data: Moon, Feinstein.
Drafting of the manuscript: Moon, Higgins.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: Moon, Ahadiat.
Administrative, technical, or material support: Higgins.
Supervision: Higgins, Sutton, Wysong.
Conflict of Interest Disclosures: Dr Wysong reported being an unpaid scientific advisor to Castle Biosciences on a squamous cell carcinoma research study unrelated to this paper. No other disclosures were reported.
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