Evaluation of MITF, SOX10, MART-1, and R21 Immunostaining for the Diagnosis of Residual Melanoma In Situ on Chronically Sun-Damaged Skin

Melanocyte Density in the Diagnosis of Melanoma In Situ in Sun-Damaged Skin

ABSTRACT

Histologic differentiation between melanoma in situ in chronically sun-damaged skin (CSDS) [lentigo maligna (LM)] and CSDS without malignancy is difficult because signs of melanocyte activation and proliferation are found in both. A potentially reliable and quantifiable criterion is melanocyte density (MD). Here, we evaluated whether and to what extent MD allows the distinction between LM and CSDS, which is particularly relevant for the evaluation of borderline cases and surgical margins.Articles assessing MD in LM and/or CSDS were evaluated in a systematic review. The results were categorized and compared according to staining. Cutoff values were included whenever stated.Twenty articles matched the selection criteria. Six hundred forty-four samples of CSDS and 227 samples of LM were considered. In each individual study, mean MD scores were higher for LM than for CSDS. However, looking at the overall study situation, it becomes clear that the data are very heterogeneous and show overlaps. Therefore, no reliable orientation value can be derived. Only 1 article defined a cutoff value.The data of MD in LM in contrast to CSDS were sparse, and a defined cutoff value was only mentioned in 1 article for microphthalmia-associated transcription factor, which cannot yet be generalized. Especially regarding the importance for the definition of surgical resection margins, this unsatisfactory data set highlights the need for further studies. More precise diagnostic criteria could spare some patients extensive and possibly disfiguring surgery.

An Update and Review of Clinical Outcomes Using Immunohistochemical Stains in Mohs Micrographic Surgery for Melanoma

BACKGROUND

Mohs micrographic surgery (MMS) provides optimal margin control through complete peripheral and deep margin assessment. The treatment of melanoma using MMS has historically been limited by difficulty in interpreting melanocytes using frozen sections. Immunohistochemical (IHC) staining, a technique whereby chromogen-tagged antibodies are used to detect antigens of interest, has revolutionized the surgical treatment of melanoma.

OBJECTIVES

This article provides an update and literature review of current IHC stains used in MMS for melanoma, their sensitivities and specificities, and clinical outcomes.

MATERIALS AND METHODS

A PubMed search was performed using keywords including "immunohistochemistry," "staining," and "Mohs surgery." Articles related to the use of IHC staining for the treatment of melanoma with MMS were included.

RESULTS

Six IHC stains met the criteria for the review including melanoma antigen recognized by T cells (MART-1), SRY-related HMG-box (SOX10), microphthalmia-associated transcription factor, HMB-45, MEL-5, S-100, and preferentially expressed antigen in melanoma.

CONCLUSION

The adaptation of IHC methods to frozen sections has enabled MMS to become a preferred treatment option for melanoma in special-site areas. Future studies are needed to standardize IHC techniques and to define best practices when using frozen section in the treatment of melanoma.

Staged Excision of Lentigo Maligna of the Head and Neck: Assessing Surgical Excision Margins With Melan A, SOX10, and PRAME Immunohistochemistry

BACKGROUND

Staged excision has emerged as a superior treatment option for lentigo maligna (LM) of the head and neck when compared with conventional wide local excision. Assessing surgical excision margins for remaining LM poses a diagnostic challenge.

OBJECTIVES

To determine whether immunohistochemical (IHC) staining with SOX10 and preferentially expressed antigen in melanoma (PRAME) aids in diagnosing LM on excision margins compared with conventional hematoxylin and eosin and Melan A IHC staining.

METHODS

This study included cases of LM of the head and neck treated with staged excision. Histological findings were reviewed according to standard criteria for the diagnosis of LM and compared with the results after IHC staining for Melan A, SOX10, and PRAME.

RESULTS

The cohort consisted of 35 sections. Based on hematoxylin and eosin and Melan A IHC staining, 23 sections were diagnosed as LM by the initial pathologist. Further staining with SOX10 IHC showed only 8 to be consistent with a diagnosis of LM and 9 revealing features of actinic melanocyte hyperplasia. PRAME was positive in 5 of the 8 cases of LM and negative in all 9 cases of actinic melanocyte hyperplasia (P = 0.009). The presence of melanocyte nests (P = 0.29) and pagetoid spread (P = 0.003) was the most reliable histological findings distinguishing LM from its mimics.

CONCLUSION

SOX10 is a more specific and sensitive marker for melanocytes when assessing for LM on excision margins compared with Melan A. The addition of PRAME can be useful to confirm or exclude the diagnosis in challenging cases.

Systematic Review of the Role of Mohs Micrographic Surgery in the Management of Early-Stage Melanoma of the Head and Neck

BACKGROUND

The role of Mohs micrographic surgery (MMS) in the management of melanoma of the head and neck (HNM) has been controversial. The authors systematically reviewed the local recurrence rate of melanoma in situ (MIS) and T1a melanomas using MMS compared with conventional wide local excision (WLE) and staged excision (SE).

OBJECTIVE

To systematically review the local recurrence rate of early-stage melanomas of the HNM treated with MMS versus WLE or SE.

METHODS AND MATERIALS

A search of English medical literature was conducted through the common databases until November 26, 2019. Using PRISMA guidelines for the treatment of MIS and T1a melanoma with MMS, WLE, or SE, our search yielded a total of 32 articles.

RESULTS

Mohs micrographic surgery has a lower local recurrence rate for early-stage melanomas over both SE and WLE {pooled recurrence risk 0.8% (95% confidence interval [CI] 0.4-1.1) versus 2.5% (95% CI 1.5-3.4) versus 8.7% (95% CI 5.1-12.2) (p < .001), respectively}.

CONCLUSION

Mohs micrographic surgery may offer a lower recurrence rate than SE or WLE in the management of early-stage melanomas of the face or HNM. Further clinical validation in a randomized controlled trial is required.

Digital Quantification of Melanocytic Density in Resection Margins of Lentigo Maligna Using SOX10 Versus Hematoxylin-Eosin Staining

ABSTRACT

Lentigo maligna (LM) represents an overgrowth of atypical melanocytes at the dermal-epidermal junction of chronically sun-damaged skin. The presence of LM on sun-damaged skin poses a diagnostic challenge because the solar-induced melanocytic hyperplasia makes it difficult to assess the LM margins. Melanocytic density can be used to discriminate sun-damaged skin from LM. The aim of this study was to quantify the melanocytic density at the surgical margins of scanned whole-slide images of LM comparing sections stained with H&E and SOX10. Twenty-six surgically excised LM diagnosed at the Department of Pathology at Sahlgrenska University Hospital were collected. The slides that contained the closest surgical margin or harbored the highest density of melanocytes at the margin were selected for serial sectioning using H&E and SOX10. Whole-slide imaging at ×40 magnification was used, and a circular field with a diameter of 0.5 mm at the surgical margin was superimposed on the image. Five blinded pathologists reviewed the slides in a randomized order. In the majority of the cases (24/26), the pathologists identified more melanocytes on the SOX10 slides than those on the H&E slides. On average, 2.5 times more melanocytes were counted using SOX10 compared with H&E (P < 0.05). Furthermore, the average group SD on the H&E slides was 4.12 compared with 2.83 on the SOX10 slides (P = 0.004). Thus, the use of SOX10 staining leads to higher melanocytic density counts compared with H&E staining when assessing the surgical margins of LM. The use of SOX10 staining also significantly decreased the interobserver variability between pathologists.

Reporting regression with melanoma in situ: reappraisal of a potential paradox

Melanoma in situ (MIS) is a form of radial growth phase melanoma in which the proliferation of malignant cells is confined to the epidermis. Histologic features are invaluable in recognition of MIS. Regression occurs when the host's immune system attacks the primary melanocytic tumor cells via tumor infiltrate lymphocytes, resulting in a fibrotic component. Various criteria have been proposed to assess the extent of histologic regression. Some authors define regression based on histologic features of the dermis, which is inappropriate for MIS. Specific dermatoscopic findings of regression in MIS have been reported including peppering, grey-blue areas, white areas, and blue-whitish veils. Many studies assess the impact of histologic regression on invasive melanoma prognosis, but no studies to-date have considered the effect of histologic regression exclusively in patients with MIS. The literature to-date does not suggest evaluation and management should be modified if histologic regression is present in MIS. Studies specifically investigating the effect of histologic regression on MIS prognosis are needed to inform evidence-based practices.

Pathology of Melanoma

Melanoma is an aggressive malignancy arising from melanocytes in the skin and rarely in extracutaneous sites. The understanding of pathology of melanoma has evolved over the years, with the initial classifications based on the clinical and microscopic features to the current use of immunohistochemistry and genetic sequencing. The depth of invasion and lymph node metastasis are still the most important prognostic features of melanoma. Other important prognostic features include ulceration, lymphovascular invasion, mitosis, and tumor-infiltrating lymphocytes. This article reviews the pathology of melanoma and its precursor lesions, along with the recent advances in pathologic diagnosis of melanoma.