Concordance of Frozen and Permanent Sections for the Diagnosis of Skin Lesions

Postoperative permanent section evaluation of Mohs micrographic surgery debulk specimens does not result in upstaging of cutaneous squamous cell carcinoma compared to stage at the completion of surgery: A retrospective case series

Background

Mohs micrographic surgery (MMS) is used for the treatment of high-risk cutaneous squamous cell carcinoma (cSCC). MMS examines the surgical margins in real time and does not commonly examine the central component of the tumor.

Objective

To determine if debulk specimens provide additional details relevant to tumor staging not gained from routine MMS.

Methods

A retrospective chart review of debulk specimens taken during MMS for cSCC was performed. Dermatopathology reports were analyzed and tumors were staged using Brigham and Women's Hospital and American Joint Committee on Cancer's 8th edition staging systems.

Results

Permanent section evaluation of debulk specimens did not result in clinically meaningful information for staging that could not be gained from MMS layers or initial biopsy analysis.

Limitations

A single institution, and a small sample size of 39 tumors.

Conclusions

Evaluation of debulk specimens during MMS may not always be an effective use of time or health care resources.

Real-time Analysis of Skin Biopsy Specimens With 2-Photon Fluorescence Microscopy

Importance

Nonmelanoma skin cancers (NMSCs) are primarily diagnosed through paraffin section histologic analysis of skin biopsy specimens that requires days to weeks before a formal diagnosis is reported. Two-photon fluorescence microscopy (TPFM) has the potential for point-of-care diagnosis of NMSC and other dermatologic conditions, which could enable same-visit diagnosis and treatment.

Objective

To demonstrate that TPFM imaging of NMSC can occur within minutes of obtaining biopsies and provide similar histological features to those of conventional histology and evaluate TPFM diagnostic performance with respect to conventional histology.

Design, Setting, and Participants

This comparative effectiveness pilot study examined 29 freshly excised biopsies from confirmed NMSC lesions in patients presenting for treatment. Biopsies underwent imaging immediately with TPFM on site at Rochester Dermatologic Surgery (Victor, New York) between October 2019 and August 2021. The imaged biopsies were subsequently submitted for paraffin histology to produce coregistered images. Twelve of these coregistered image pairs (41.4%) were used as a training set. Fifteen (51.7%) were used in a masked evaluation by a board-certified dermatopathologist. Two (6.9%) were excluded from the study before evaluation because they could not be coregistered.

Main Outcomes and Measures

Sensitivity, specificity, and accuracy of TPFM for NMSC biopsies were evaluated compared with conventional histology.

Results

Fourteen of the 15 biopsy specimens (93.3%) in the evaluation set were identically diagnosed with TPFM and paraffin histology. The TPFM had 100% sensitivity (95% CI, 48%-100%), 100% specificity (95% CI, 69%-100%), and 100% accuracy (95% CI, 78%-100%) for basal cell carcinoma diagnosis. For squamous cell carcinoma diagnosis, TPFM had 89% sensitivity (95% CI, 52%-100), 100% specificity (95% CI, 54%-100%), and 93% accuracy (95% CI, 68%-100%). For overall NMSC diagnosis, TPFM had a 93% sensitivity (95% CI, 66%-100%), 100% specificity (95% CI, 3%-100%), and 93% accuracy (95% CI, 68%-100%). Examination of the 1 discordant pair revealed mismatched imaging planes as the source of error.

Conclusions and Relevance

The results of this comparative effectiveness pilot study suggest that TPFM captures histological characteristics of NMSC that are present in conventional histology, which reveals its potential as a rapid, point-of-care diagnostic alternative that does not need extensive sample preparation or retraining for image evaluation. Further validation of TPFM imaging performed for a larger cohort is needed to fully evaluate its diagnostic accuracy and potential effect within the field.

Diagnostic Biopsy via In-Office Frozen Sections for Clinical Nonmelanoma Skin Cancer

BACKGROUND

Treatment of nonmelanoma skin cancer (NMSC) by Mohs surgery has traditionally relied on previous pathologic evaluation of paraffin-embedded tissue. Tissue processing by frozen sections allows for expedited diagnosis and treatment; however, data on its accuracy are limited.

OBJECTIVE

To measure the accuracy and outcomes of biopsy via frozen sections for clinical NMSC.

METHODS

Biopsies of clinical NMSCs processed via frozen sections with in-office diagnosis rendered by one Mohs surgeon were retrospectively reviewed by one board-certified dermatopathologist. Discordant diagnoses were re-read in blinded fashion by both physicians. If still discordant, final diagnosis was determined by consensus discussion. Inter-rater reliability was calculated using Cohen's kappa statistic.

RESULTS

Two hundred ninety-seven lesions from 208 patients were included. Correlation between in-office and final diagnosis was 0.876 indicating "almost perfect" concordance. Sensitivity and specificity of in-office diagnosis for detecting malignancy were 98.1% and 94.4%. Seven cases (2.0%) had a clinically relevant change in final diagnosis, but appropriate treatment had been rendered. Two benign lesions (0.7%) initially diagnosed as malignant underwent excision.

CONCLUSION

In-office biopsy via frozen sections is highly accurate in confirming NMSC. This practice may speed diagnosis and treatment thus improving outcomes and patient satisfaction.

Histopathologic upgrading of cutaneous squamous cell carcinomas during Mohs micrographic surgery: A retrospective cohort study

BACKGROUND

Initial biopsies of cutaneous squamous cell carcinomas (cSCCs) may not reveal aggressive histologic features, which would otherwise inform appropriate surgical management and patient education.

OBJECTIVE

To assess the incidence of, and risk factors for, histopathologic upgrading of cSCC during Mohs micrographic surgery (MMS).

METHODS

This was a retrospective cohort study of invasive cSCCs treated with MMS between 2017 and 2019 at 1 academic institution. An "upgrade" was defined as a lesser degree of differentiation (poor or moderate) and/or bony or perineural invasion identified during MMS that was not reported in histopathologic evaluation of the initial biopsy.

RESULTS

Of the 1558 tumors studied, 115 (7.4%) were upgraded during MMS. In multivariate logistic regression analysis, male sex, prior field treatment, location on the ear/lip, rapid growth of cSCC, and tumor diameter ≥2 cm were significant predictors of tumor upgrading. Upgraded tumors were more likely to require ≥3 MMS stages to clear, complicated closure (flap or graft), or outside (referral) repairs.

LIMITATIONS

Single-center study, retrospective, and inter-rater variability.

CONCLUSIONS

A significant proportion of cSCCs is histopathologically upgraded with more aggressive features during MMS. Routinely documented patient and tumor characteristics can predict tumor upgrading and assist clinicians in directing the management of potentially high-risk cSCC patients.

Frozen section diagnosis for non-melanoma skin cancers: correlation with permanent section diagnosis

Frozen section pathology is routinely used for margin assessment of non-melanoma skin cancer (NMSC). Frozen section can also be used for the primary diagnosis of several skin lesions. Limited data exist on the accuracy of frozen section in the diagnosis of NMSC. We performed a retrospective chart review of 300 cases in which frozen section diagnoses were compared with permanent section diagnoses of NMSC. Frozen section and permanent section pathology were concordant 83.3% of the time, with the highest concordance rates noted for basal cell carcinoma (145/153, 95%). Our results show a high level of concordance between frozen section and corresponding permanent section pathology diagnosis for NMSC. The rapidity of frozen section tissue processing and pathology reporting makes this technique useful in dermatologic practice for immediate diagnosis and management of NMSC. Further studies should explore strategies to decrease or eliminate discrepancies between frozen and permanent section diagnosis.

The use of frozen section in the excision of cutaneous malignancy: a Queensland experience

Frozen section is known to be a valuable tool in the setting of indistinct lesions, lesions in cosmetically or functionally important areas, and those with recurrent or residual tumors. Most non-Mohs surgery studies comparing frozen section with paraffin sections suggest a concordance rate of 85% to 90%, whereas studies with Mohs surgery often suggest concordance rates of 95% to 98%. We do not perform Mohs surgery at our institutions but feel that the accuracy of frozen section is relatively high. Frozen-section data from between 2005 and 2011 was analyzed, and a total of 150 cases was found and assessed. Most of the cases were basal cell carcinomas and squamous cell carcinomas, with most arising in the head and neck region. Half of the resections were for previous incomplete margins with the other half being primary excisions. The frozen section was accurate in 97.7% of the cases when compared with the formal paraffin sections. However, the incomplete rate was higher at 14.8% because of patients with known positive margins on frozen section and the use of less accurate techniques of specimen analysis. We feel that, when used appropriately, frozen section can be a reliable tool and that a negative result should provide the surgeon enough reassurance as to undertake immediate reconstruction.

Mohs frozen tissue sections in comparison to similar paraffin-embedded tissue sections in identifying perineural tumor invasion in cutaneous squamous cell carcinoma

BACKGROUND

Perineural invasion (PNInv) in cutaneous squamous cell carcinoma (cSCC) increases the risk of recurrence, possibly because of suboptimal identification on frozen or paraffin-embedded tissue sections. Perineural inflammation (PNInf) may portend PNInv.

OBJECTIVE

We sought to correlate identification of PNInv and PNInf in hematoxylin-eosin-stained Mohs frozen sections with PNInv and PNInf identified in similarly oriented paraffin-embedded sections obtained in cases of cSCC.

METHODS

We reviewed same patient Mohs frozen and paraffin-embedded tissue sections for all patients presenting within a 2-year period to our Mohs micrographic surgical unit for removal of cSCC with PNInv or PNInf identified on either type of tissue section.

RESULTS

Of 537 patients undergoing surgical resection of cSCC, 21 (3.9%) had either PNInv (n = 11) or PNInf (n = 10) on frozen sections. PNInv on Mohs frozen sections was identified in 11 cases and confirmed on paraffin-embedded sections in 9 cases (82%). Paraffin-embedded sections failed to identify PNInv present in Mohs frozen sections in two (2/11), or 18% of cases. PNInf on Mohs frozen sections was confirmed on paraffin-embedded sections in 3 cases (30%), but PNInv was identified in 5 cases (50%).

LIMITATIONS

Our results are a retrospective case review from a specific time period by one institution. Furthermore, it is impossible to compare identical tissue specimens using two sequential tissue processing techniques.

CONCLUSION

PNInv can be accurately identified with Mohs frozen sections. PNInf on Mohs frozen sections suggests the presence of PNInv and requires further histologic investigation.