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.

Staged margin control techniques for surgical excision of lentigo maligna

For melanoma in situ (MIS) arising in chronically photodamaged skin (a.k.a. lentigo maligna, LM), the preferred treatment remains surgical excision. Yet, the standard 5-mm margins of excision recommended for other subtypes of MIS have proven insufficient for LM, due to the its indistinct borders. In this report, authors review specialized surgical techniques for the treatment of LM that focus on meticulous assessment of peripheral margins prior to closure (staged margin control) conducted with analysis of either frozen or permanent histologic sections. Techniques utilizing permanent sections include variations of the ''square'', ''perimeter'', and ''contoured'' excisions, and recurrence rates with these techniques are reportedly low based on short-term follow-up. Similarly, Mohs micrographic surgery (MMS) has been reported to be effective in LM, with recurrence rates generally less than 1% over three-five years of follow-up. In order to simplify margin assessment for MMS, many investigators have begun to rely on intraoperative immunohistochemistry (IHC) to identify melanocytes in frozen sections, and MART-1 is surrently the preferred immunostain for this purpose. Other methods of IHC are currently under investigation. Regardless, surgical methods that employ this degree of margin assessment offer superior cure rates compared to standard excision, and should be seriously considered when encountering patients with LM. Total peripheral margin assessment using staged excisions and analysis of permanent sections appears to be a simple and effective alternative to MMS, especially for institutions that prefer examination of permanent sections to frozen sections.

Nature of inflammatory infiltrate in superficial cutaneous malignancies during topical imiquimod treatment

Topical imiquimod (IQ) is an effective treatment for genital warts and various malignant tumors of the skin. IQ acts through the Toll-like receptor 7 leading to the production of cytokines and chemokines such as interferons, interleukins, and growth factors. We investigated the composition of the inflammatory cell infiltrate before, during, and after the treatment of 10 superficial cutaneous malignancies (melanoma in situ (n = 4), melanoma metastasis (n = 1), squamous cell carcinoma in situ (n = 4), and basal cell carcinoma (n = 1) with 5% IQ cream. Immunophenotyping revealed in all cases during treatment an increased population of T-lymphocytes positive for CD3, CD4 and CD8, as well as a considerable number of cytotoxic cells (TIA-1+, granzyme B+) and plasmacytoid dendritic cells (CD 123+). These findings further support previous investigations that the antitumor effects of IQ result from an enhanced cytotoxic T-cell mediated immune response and from the recruitment of plasmacytoid dendritic cells to the skin. The population of infiltrative inflammatory cells was similar in all patients irrespective of the type of tumor.

S100A protein expression in the distinction between lentigo maligna and pigmented actinic keratosis

Lentigo maligna (LM), a type of malignant melanoma in situ, and pigmented actinic keratosis (PAK) may have similar clinical appearances but are different in prognosis and treatment. Diagnosis is established by skin biopsy. In certain cases, microscopic features may be very similar in both entities, making it difficult to determine whether the pigmented atypical cells are keratinocytes or melanocytes. Immunohistochemical markers can be useful for the identification of melanocytes in these cases. There are limitations to the use of some standard immunohistochemistry markers, however. S100 proteins are a varied group of proteins that are of special interest because of their dysregulated expression in neoplastic disorders. Their expression is changed during malignant transformation, progression, and/or metastasis in various cell lines and tumors, including melanomas. Our study analyzed the expression of several of the S100 protein subtypes (S100A2, S100A6, and S100A8/A9 or A12) in 38 LM cases and 44 PAK cases to define their potential value in the distinction between these entities together with their role in the development of early malignant melanoma of the skin. The results showed an upregulation of S100A2 protein in atypical keratinocytes in PAK and in normal keratinocytes adjacent to melanoma cells in LM. There was also an upregulation of S100A8/A9 or A12 protein, as detected by the antibody MAC387, in normal keratinocytes adjacent to both atypical keratinocytes and melanocytes in PAK and LM, respectively. There were statistically significant differences in the level of positive cells and in the pattern of immunoreactivity for anti-S100A2 and MAC387 in each entity, however. Moreover, the findings of our study support the notion that melanocyte-keratinocyte interactions are abnormal in both of these disease entities and may be involved in their progression.

Concurrent Ki-67 and p53 immunolabeling in cutaneous melanocytic neoplasms: an adjunct for recognition of the vertical growth phase in malignant melanomas?

Ki-67 labeling of paraffin sections has been correlated with the number of cells in non-G(o) phases of the replicative cell cycle, and this immunohistochemical technique has been applied to the evaluation of a variety of human neoplasms. Similarly, immunolabeling for p53 protein has been used to detect mutations in the corresponding gene, as a reflection of possible cellular transformation in the same context. Both of these techniques were applied to 253 melanocytic tumors of the skin to assess their possible utility in the diagnosis and subcategorization of such lesions. They included 76 banal (common) nevi (CN), 39 Spitz nevi (SN), 62 superficial spreading malignant melanomas in radial growth (SSMMs), 32 nodular malignant melanomas (NMMs), 21 lentigo maligna melanomas in radial growth (LMMs), and 23 melanomas arising in association with preexisting compound nevi (MCN). One hundred cells were counted randomly in each tumor, and dark, exclusively nuclear reactivity was scored as positive labeling; results were recorded as percentages. Negligible Ki-67 and p53 labeling was seen in CN and SN, at a level that was similar to that obtained in cases of LMM and MCN. The largest proportion of Ki-67-positive and p53-positive cells was observed in NMMs, followed by SSMMs. Radial growth-phase SSMMs and LMMs demonstrated immunoprofiles that were similar to those of melanocytic nevi, and MCN did so as well. The prototypical malignant melanocytic tumor representing the vertical growth phase-nodular melanoma--demonstrated a statistically significant difference from all other lesions in this study with respect to Ki-67 index (P = .008, chi2) and p53 reactivity (P < .000001, chi2). Subsequent concurrent use of a Ki-67 threshold index of 10% and a p53 index of 5% correctly indicated the presence of vertical growth in 75% of NMMs, whereas only 8% of radial growth phase melanomas of other types were colabeled at the same levels of reactivity for the two markers (P < .00001, chi2). Thus, although the distinction between benign and malignant melanocytic tumors could and should not be based on immunohistology for Ki-67 and p53, these results suggest that the latter determinants may, in fact, be used as an adjunct to morphology in the recognition of the vertical growth phase in cutaneous malignant melanomas.

Up-regulation of growth hormone receptor immunoreactivity in human melanoma

Growth hormone (GH) exerts its regulatory functions in controlling metabolism, balanced growth and differentiated cell expression by acting on specific receptors, which trigger a phosphorylation cascade resulting in the modulation of numerous signalling pathways, and dictate gene expression. Immunohistochemical techniques were used to demonstrate the presence of growth hormone receptors in 126 formalin-fixed, paraffin-embedded melanocytic tumours comprising melanocytic naevi, superficial spreading melanoma, nodular melanoma, lentigo maligna melanoma and metastatic melanomas. The relative proportion of positive cells and intensity of staining was higher in neoplastic cells, compared to normal cutaneous cells. Of the 76 cases of common melanocytic naevi (CMN) studies, 46 were weakly reactive with MAb 263. Heterogeneity of immunoreactivity was found in primary melanoma lesions with a variable range of positive cells. Of 37 cases studied, 34 were moderately to strongly positive. Immunoreactivity showed subcellular localization of the GH-receptor in cell membranes, was predominantly cytoplasmic, but strong nuclear immunoreaction was also apparent in many instances. The nuclear localization of immunoreactivity is the result of nuclear GH-receptor/binding protein, identically to the cytosolic and plasma growth hormone binding protein. Intense immuno-reactivity was also observed in the cellular Golgi area of established cell lines and cultured tissue-derived cells in exponential growth phase, indicating cells are capable of GH-receptor synthesis. In the primary lesions, dermal tumour cells tended to be more immunoreactive relative to those seen in the dermal region. Metastatic lesions in various organs also expressed growth hormone receptors in secondary tumour cells and all of the metastatic cases were positive. The expression of GH-receptors in human melanoma cells means that these cells are directly responsive to GH action and that GH may stimulate local production of IGF-I, which then acts in an autocrine mechanism.

Margin control for lentigo maligna

BACKGROUND

Lentigo maligna is an in situ malignant melanoma for which the treatment of choice is surgical excision. The current recommendation is local resection with a 0.5 to 1.0 cm margin of normal skin. Because many lesions occur on the face, the narrowest possible margin reduces the amount of scarring. Controversy surrounds the use of Mohs micrographic surgery to preserve normal skin and resect the lentigo maligna.

OBJECTIVE

The purposes of this prospective study were to determine the narrowest possible margin of resection of lentigo maligna and the accuracy of frozen and fixed histologic specimens from those margins. In addition, the benefit of adjunctive immunoperoxidase staining with antibodies to S-100 protein and HMB-45 monoclonal antibody was examined retrospectively.

METHODS

A Wood's light was used to delineate the clinical margin in 16 cases of lentigo maligna that were resected with serial excisions 0.3, 0.6, 1.0, and 1.3 cm from the clinical border of the tumor. Frozen sections were confirmed by fixed histopathologic specimens. Subsequently these tissue blocks were examined with antibodies to S-100 protein and HMB-45 monoclonal antibodies. Patients were observed 5 to 9 years.

RESULTS

One of the 16 patients had a recurrence 8 years after surgery. Although lesions with a diameter less than 2.0 cm had narrower margins of resection, the majority of lesions were resected with a margin of 0.6 to 1.0 cm. Lesions larger than 3.0 cm in diameter required a margin of resection greater than 1.0 cm. The antibody to S-100 protein was neither sensitive nor specific enough to assist with identification of the process. HMB-45 monoclonal antibody was sensitive and assisted in the identification of atypical melanocytes.

CONCLUSION

The modifications of Mohs micrographic surgery including the use of fixed histopathologic specimens and the use of HMB-45 monoclonal antibody to help delineate atypical melanocytes offer the possibility of narrower margins of resection for lentigo maligna.

A quantitative immunohistochemical evaluation of lentigo maligna and pigmented solar keratosis

Pigmented solar keratosis (PSK) is sometimes clinically indistinguishable from lentigo maligna, a form of malignant melanoma in situ. Occasionally histologic diagnosis is also difficult. Accurate diagnosis is essential, as the treatment and prognosis for each condition differs considerably. To determine whether there was a significant overlap in the number of melanocytes in these sun-damaged skin lesions, or whether immunohistochemistry might be helpful in the differential diagnosis, the authors examined skin biopsy specimens from 26 patients with obvious lentigo maligna and 15 patients with PSK using 3 monoclonal antibodies (HMB-45, NK1C3, and vimentin) and 1 polyclonal antibody (S-100 protein). Formalin-fixed paraffin sections were immunostained with each of the above antibodies, and immunopositive cells per mm2 of epidermis were counted. The difference between lentigo maligna and PSK counts was statistically significant at a level of P < .0001; furthermore, there was almost no overlap between the two groups. The sensitivity for the diagnosis of lentigo maligna was high with all antibodies. However, HMB-45 had the highest sensitivity and the lowest false-positive rate and was visually most pleasing. Using a cut-off count of 60 cells per mm2 of epidermis, HMB-45 had a sensitivity of 96% and a 0% false-positive rate. In this study, lentigo maligna was easily differentiated from PSK. The real value of immunohistochemistry in the differential diagnosis of these pigmented lesions should be tested in a prospective study using cases that are difficult to diagnose by routine light microscopy.