Are En Face Frozen Sections Accurate
To assess the diagnostic accuracy of margin evaluation of melanocytic lesions using en face frozen sections compared with standard paraffin-embedded sections, we studied 2 sets of lesions in which en face frozen sections were used for analysis of surgical margins (13 from malignant melanomas [MMs] and 10 from nonmelanocytic lesions [NMLs]). Routine permanent sections were cut after routine processing. The slides were mixed and coded randomly. Fifteen dermatopathologists examined the cases separately. Margin status was categorized as positive, negative, or indeterminate. Kappa statistics were calculated per dermatopathologist and per case.
One case from each group was excluded because epidermis was not available in the routine sections. Of 330 evaluations (22 cases, 15 dermatopathologists), there were 132 diagnostic discrepancies (40.0%): 66 each for MM and NML (mean per case for both diagnoses, 6). In 9 instances (6.8%), the change was from positive (frozen) to negative (permanent) and in 43 (32.6%), from negative (frozen) to positive (permanent). There was poor agreement between frozen and permanent sections (
range per dermatopathologist, -0.1282 to 0.6615).
If permanent histology is considered the "gold standard" for histologic evaluation, en face frozen sections are not suitable for accurate surgical margin assessment of melanocytic lesions.
Frozen sections are used widely in pathology and dermatopathology to provide a quick diagnosis for a variety of lesions. Some previous studies recommended using frozen sections for histologic differentiation between nevus and malignant melanoma (MM). However, the method of freezing and cryostat cutting results in slides of a lower technical quality than those from formalin-fixed, paraffin-embedded tissue. Therefore, it may be more difficult to evaluate morphologic detail in frozen sections. Mainly for that reason, although several authors have advocated the use of frozen sections for the diagnosis of pigmented lesions, including lentigo maligna, other authors have discouraged that method.
In addition to the technical problems associated with freezing, the evaluation of frozen sections to determine surgical margin status in pigmented lesions of the head and neck is complicated because of the presence of scattered atypical melanocytes, secondary to actinic damage. Analysis of sections cut perpendicular to the surgical margin permits examination of any possible lesion in the center of the specimen and its relation to the surgical margin. In contrast, in en face sections (ie, sections cut parallel to the surgical margin), the detection of an isolated, atypical melanocyte may represent either lentigo maligna at the margin or just a background of sun-damaged skin.
We assess the diagnostic accuracy of margin evaluation of melanocytic lesions using frozen sections cut en face compared with using paraffin-embedded material.
To assess the diagnostic accuracy of margin evaluation of melanocytic lesions using en face frozen sections compared with standard paraffin-embedded sections, we studied 2 sets of lesions in which en face frozen sections were used for analysis of surgical margins (13 from malignant melanomas [MMs] and 10 from nonmelanocytic lesions [NMLs]). Routine permanent sections were cut after routine processing. The slides were mixed and coded randomly. Fifteen dermatopathologists examined the cases separately. Margin status was categorized as positive, negative, or indeterminate. Kappa statistics were calculated per dermatopathologist and per case.
One case from each group was excluded because epidermis was not available in the routine sections. Of 330 evaluations (22 cases, 15 dermatopathologists), there were 132 diagnostic discrepancies (40.0%): 66 each for MM and NML (mean per case for both diagnoses, 6). In 9 instances (6.8%), the change was from positive (frozen) to negative (permanent) and in 43 (32.6%), from negative (frozen) to positive (permanent). There was poor agreement between frozen and permanent sections (
range per dermatopathologist, -0.1282 to 0.6615).
If permanent histology is considered the "gold standard" for histologic evaluation, en face frozen sections are not suitable for accurate surgical margin assessment of melanocytic lesions.
Frozen sections are used widely in pathology and dermatopathology to provide a quick diagnosis for a variety of lesions. Some previous studies recommended using frozen sections for histologic differentiation between nevus and malignant melanoma (MM). However, the method of freezing and cryostat cutting results in slides of a lower technical quality than those from formalin-fixed, paraffin-embedded tissue. Therefore, it may be more difficult to evaluate morphologic detail in frozen sections. Mainly for that reason, although several authors have advocated the use of frozen sections for the diagnosis of pigmented lesions, including lentigo maligna, other authors have discouraged that method.
In addition to the technical problems associated with freezing, the evaluation of frozen sections to determine surgical margin status in pigmented lesions of the head and neck is complicated because of the presence of scattered atypical melanocytes, secondary to actinic damage. Analysis of sections cut perpendicular to the surgical margin permits examination of any possible lesion in the center of the specimen and its relation to the surgical margin. In contrast, in en face sections (ie, sections cut parallel to the surgical margin), the detection of an isolated, atypical melanocyte may represent either lentigo maligna at the margin or just a background of sun-damaged skin.
We assess the diagnostic accuracy of margin evaluation of melanocytic lesions using frozen sections cut en face compared with using paraffin-embedded material.