Differential diagnosis of heavily pigmented melanocytic lesions: challenges and diagnostic approach

An Optimized Melanin Depigmentation Method for Histopathological and Immunohistochemical Staining of Formalin-Fixed Paraffin-Embedded Tissues

Introduction. The difficulty in diagnosis of severe melanocytic lesions is a problem to be overcome in pathological practice. Melanin bleaching is an effective approach to ameliorate melanin disturbances in severely pigmented lesions. Although various methods for improving melanin pigmentation in immunohistochemical staining have been reported, these depigmentation methods still need to be optimized and standardized. In this study, the coloring efficiency of 3,3'-diaminobenzidine (DAB) and alkaline phosphatase (AP) after melanin depigmentation was compared under the automatic immunohistochemical staining platform. Methods. The applicability of the optimized depigmentation method was validated in 10 formalin-fixed paraffin-embedded (FFPE) blocks of ocular melanoma tissues. Specimens were demelaninized with 10% hydrogen peroxide at 60°C for immunohistochemical staining (Melan-A and SOX10), and tissue chromogenic staining was performed with DAB and AP detection systems, respectively. Results. The optimized depigmentation method including immunohistochemistry (IHC) could be completed in 3 h, effectively preserving cell morphology and immunoreactivity. Among these, the color-rendering effect and contrast of AP are better than DAB. Conclusion. This optimized method can effectively remove melanin and improve the accuracy of IHC staining interpretation. AP staining has better visibility and readability without the interference of residual melanin. The comparison results showed that after melanin depigmentation, the immunohistochemical staining agent was replaced with red AP, which avoided the misjudgment caused by brown DAB when melanin depigmentation was incomplete. This improved method can be applied to future histopathological and immunohistochemical staining of melanin-deposited tissues.

A Novel Punch Technique for Facial Pigmented Melanocytic Nevus

The punch tool is a swift and practical instrument in the facial pigmented melanocytic nevus. However, few studies have evaluated the efficacy of the method for facial pigmented nevus. The aim of this study was to evaluate the practicability and effectiveness of removing facial pigmented nevus by punch biopsy technique. This was an observational study of patients with facial pigmented nevus in the Hospital of Plastic Surgery, Weifang Medical University. The ages of patients ranged from 15 to 36 years (average, 25 y). The outcome evaluations included Vancouver Scar Scale (VSS) score, esthetic appearance, and patient satisfaction. Following standard procedures, preoperative surgical excision was performed with safety margins. Anatomopathologic analysis of the surgical specimen was used as the gold standard to evaluate the accuracy of diagnosis by punch biopsy. From January 2019 to January 2020, this punch technique was carried out on 96 patients (151 pigmented nevus) with 35 melanocytic nevus on the forehead, 39 on the cheek, 21 on the eyelid, and 45 on the nose, whereas 11 were on nasolabial folds. The diameters of pigmented nevus are 0.5 to 10 mm on the face. All patients were evaluated at a follow-up visit ranging from 6 to 20 months (average, 11±1.5 mo) and healed with no complication. The histopathological examinations of the skin lesions showed benign outcomes. The mean Vancouver Scar Scale were 1.1±0.4. Ideal cosmetic and functional outcomes were achieved in 94 patients (97.9%). All patients achieved complete satisfaction except 2 patients with partial satisfaction. No recurrences and complications were recorded. This study demonstrated that the punch technique is an effective method to remove facial pigmented melanocytic nevus with acceptable functional and esthetic outcomes without relapse.

A Fast and Automated Melanin-bleaching Method for Histopathologic Evaluation of Pigmented Melanoma Tissues

Histopathologic examination of highly pigmented melanoma tissues has always been a challenge for pathologists. The high concentration of melanin pigment is an obstacle for immunohistochemistry and the ensuing evaluation. Therefore, removing melanin has become a crucial step for processing heavily pigmented melanoma samples. Several bleaching techniques have been proposed in the past, however, the most commonly used methods are time-consuming and poorly standardized. In this study, we propose a new fast and fully automated bleaching method applicable to validated immunohistochemical panels already used in the diagnosis of melanocytic tumors. The proposed bleaching protocol is based on sample pretreatment with 0.5% hydrogen peroxide and a Tris base pH 10 solution for 8 minutes at 80°C before antigen retrieval. Immunohistochemistry with HMB45, MART-1, Ki-67, SOX10, S-100, Tyrosinase, and BRAF(V600E) antibodies showed that this pretreatment removed excess melanin without affecting the tissue antigenicity and cytoarchitecture. In conclusion, we propose a new fast and automated bleaching protocol, easily transferable to a routine setting with efficient results in specimens in which the melanin pigmentation could blunt the histopathologic examination.

Melanocytic lesions with blue naevus-like (dendritic) morphology: an update with an emphasis on histopathological, immunophenotypic, and molecular features

An accurate diagnosis of melanocytic lesions requires a thorough histopathological evaluation accompanied by appropriate correlation with clinical examination findings. Although most melanocytic lesions can readily be classified as one of the defined diagnostic entities according to well-established diagnostic criteria, a subset of melanocytic lesions, particularly those with blue naevus-like (pigmented dendritic) morphology, have notoriously constituted an enduring challenge for pathologists. These lesions are rare and often show histological ambiguities, with features of both benignity and malignancy, thereby making accurate risk assessment and prediction of their biological behaviours difficult on histological grounds alone. Herein, we outline a practical and systematic approach for the diagnosis of melanocytic lesions with dendritic morphology, with a particular focus on histological and immunophenotypic features that help to distinguish one entity from another. In this review, we provide the most current knowledge on these melanocytic lesions in the literature and our experience with these rare entities, and we discuss the utility of molecular techniques as an ancillary tool, especially in histologically ambiguous and/or borderline lesions.

Parakeratosis and pagetoid melanocytosis in the evaluation of dysplastic nevi and melanoma

BACKGROUND

It is our experience that parakeratosis with pagetosis is common in early melanoma when there is no history of trauma in the anatomical site. In lesions where the differential diagnosis includes dysplastic nevus (DN) and melanoma, we hypothesize that parakeratosis may be a marker for cases in which immunohistochemistry (IHC) may identify occult pagetosis.

METHODS

We performed a retrospective case-control study on cases with a histologic differential diagnosis of DN versus melanoma, including 423 cases with parakeratosis and 125 cases without parakeratosis. IHC staining (Mart-1 and/or Sox-10) was performed in all cases. The frequency of pagetosis and diagnostic upgrades in the cases versus the controls was calculated.

RESULTS

The presence of parakeratosis was significantly associated with pagetosis (p < 0.0001). Diagnostic upgrades were more frequent in the cases with parakeratosis versus controls without parakeratosis (p = 0.0029). In the favored moderate DN group, 56% of cases were upgraded compared to 30% of the controls (p = 0.0017). In the favored mild DN and severe DN groups, there were more case upgrades compared to the controls (p = 0.1386, p = 0.2738).

CONCLUSIONS

Parakeratosis may be a useful marker to identify lesions with occult pagetosis for which IHC would be appropriate and may result in a diagnostic upgrade.

Reciprocal signaling and direct physical interactions between fibroblasts and breast cancer cells in a 3D environment

Tumorigenic cells undergo cell aggregation and aggregate coalescence in a 3D Matrigel environment. Here, we expanded this 3D platform to assess the interactions of normal human dermal fibroblasts (NHDFs) and human primary mammary fibroblasts (HPMFs) with breast cancer-derived, tumorigenic cells (MDA-MB-231). Medium conditioned by MDA-MB-231 cells activates both types of fibroblasts, imbuing them with the capacity to accelerate the rate of aggregation and coalescence of MDA-MB-231 cells more than four fold. Acceleration is achieved 1) by direct physical interactions with MDA-MB-231 cells, in which activated fibroblasts penetrate the MDA-MB-231/Matrigel 3D environment and function as supporting scaffolds for MDA-MB-231 aggregation and coalescence, and 2) through the release of soluble accelerating factors, including matrix metalloproteinase (MMPs) and, in the case of activated NHDFs, SDF-1α/CXCL12. Fibroblast activation includes changes in morphology, motility, and gene expression. Podoplanin (PDPN) and fibroblast activation protein (FAP) are upregulated by more than nine-fold in activated NHDFs while activated HPMFs upregulate FAP, vimentin, desmin, platelet derived growth factor receptor A and S100A4. Overexpression of PDPN, but not FAP, in NHDF cells in the absence of MDA-MB-231-conditioned medium, activates NHDFs. These results reveal that complex reciprocal signaling between fibroblasts and cancer cells, coupled with their physical interactions, occurs in a highly coordinated fashion that orchestrates aggregation and coalescence, behaviors specific to cancer cells in a 3D environment. These in vitro interactions may reflect events involved in early tumorigenesis, particularly in cases of field cancerization, and may represent a new mechanism whereby cancer-associated fibroblasts (CAFs) promote tumor growth.

Uncommon Histopathological Variants of Malignant Melanoma. Part 2

Despite new horizons opened by recent advances in molecular pathology, histological evaluation still remains the diagnostic gold standard regarding cutaneous melanocytic neoplasms. Several histological variants of melanoma have been described, and their knowledge is crucial for accurate diagnosis and classification of cases with unusual clinico-pathological features. Uncommon histological variants of melanoma have been described based on a broad constellation of features, including architectural pattern, stromal alterations, cytological attributes, and other morphological properties. This review is aimed at providing an extensive discussion of unusual but distinctive histopathological variants of melanoma.

Uncommon Histopathological Variants of Malignant Melanoma: Part 1

Despite new horizons opened by recent advances in molecular pathology, histological evaluation still remains the diagnostic gold standard regarding cutaneous melanocytic neoplasms. Several histological variants of melanoma have been described, and their knowledge is crucial for accurate diagnosis and classification of cases with unusual clinicopathological features. Uncommon histological variants of melanoma have been described based on a broad constellation of features, including architectural pattern, stromal alterations, cytological attributes, and other morphological properties. This review is aimed at providing an extensive discussion of unusual but distinctive histopathological variants of melanoma.

Histologic mimics of malignant melanoma

Although spongiotic (eczematous), psoriatic and cutaneous skin infections are among the most common in dermatology consultations, melanocytic lesions - including the different types of nevi and melanomas - are among those that cause a great deal of concern and stress to patients and their clinicians. A diagnosis of benign melanocytic nevus carries a very good prognosis. However, a diagnosis of melanoma might indicate more aggressive treatment, lifelong surveillance and a worse prognosis. Differentiating between these conditions is not always a straightforward process for clinicians and pathologists. Therefore, knowledge of melanoma mimickers is very important for clinicians in general, and dermatologists and pathologists in particular. In this review, we called attention to some of the more frequent benign but unusual melanocytic lesions that are of diagnostic concern for clinicians evaluating these cutaneous proliferations.

Animal-type melanoma: dog or wolf? A review of the literature and a case report

The human animal type melanoma (ATM) is a rare subtype of melanoma characterised by the proliferation of pigmented dermal epithelioid and spindled melanocytes. However, this variant of melanoma is still lacking a precise nosography definition and classification for the difficulty to be distinguished from other more common melanocytic lesions, as well as for its peculiar biological behaviour. On the other hand, the contribution of scientific literature to this issue is fragmented and limited to the description of very few cases. Starting from the presentation of a case with abnormally aggressive clinical features, here we revisit the current knowledge on ATM from its dermatologic patterns, epidemiology, demography and histopathology to the clinical management. Peculiar accuracy has also been reserved to several histopathologic criteria, which are critical for the differential diagnosis from other melanocytic diseases in junction with molecular data deriving from recent cytogenetic and mutational characterisation of this tumour.

Common and not so Common Melanocytic Lesions in Children and Adolescents

The acquired melanocytic nevus is the most common lesion encountered by pediatric pathologists and dermatopathologists in their daily practice. In most cases, there are few difficulties in histopathologic diagnosis. However, it is the acquired melanocytic lesion known as the Spitz nevus, with its intrinsic atypical features which becomes the challenge since it exists along a histopathologic and biologic continuum from the atypical Spitz tumor to spitzoid melanoma. The frustration with some of these spitzoid lesions is that even the "experts" cannot agree as to the differentiation of one from the other even at the level of molecular genetics. Other melanocytic lesions are discussed including the congenital melanocytic nevus with its proliferative nodule(s) and melanoma as the ultimate complication. Although uncommon, cutaneous melanoma in the first 2 decades is emerging as a clinical problem especially in young women in the second decade of life. These are ultraviolet-associated neoplasms whose histopathologic and prognostic features are identical to the adult experience. Considerable progress has been made over the past 15 to 20 years in our understanding of cutaneous melanocytic lesions, but gaps still exist in the important group of spitzoid lesions. It can also be anticipated that more cutaneous melanomas in children will be seen in the future based upon epidemiologic studies.

Melanoma cells undergo aggressive coalescence in a 3D Matrigel model that is repressed by anti-CD44

Using unique computer-assisted 3D reconstruction software, it was previously demonstrated that tumorigenic cell lines derived from breast tumors, when seeded in a 3D Matrigel model, grew as clonal aggregates which, after approximately 100 hours, underwent coalescence mediated by specialized cells, eventually forming a highly structured large spheroid. Non-tumorigenic cells did not undergo coalescence. Because histological sections of melanomas forming in patients suggest that melanoma cells migrate and coalesce to form tumors, we tested whether they also underwent coalescence in a 3D Matrigel model. Melanoma cells exiting fragments of three independent melanomas or from secondary cultures derived from them, and cells from the melanoma line HTB-66, all underwent coalescence mediated by specialized cells in the 3D model. Normal melanocytes did not. However, coalescence of melanoma cells differed from that of breast-derived tumorigenic cell lines in that they 1) coalesced immediately, 2) underwent coalescence as individual cells as well as aggregates, 3) underwent coalescence far faster and 4) ultimately formed long, flat, fenestrated aggregates that were extremely dynamic. A screen of 51 purified monoclonal antibodies (mAbs) targeting cell surface-associated molecules revealed that two mAbs, anti-beta 1 integrin/(CD29) and anti-CD44, blocked melanoma cell coalescence. They also blocked coalescence of tumorigenic cells derived from a breast tumor. These results add weight to the commonality of coalescence as a characteristic of tumorigenic cells, as well as the usefulness of the 3D Matrigel model and software for both investigating the mechanisms regulating tumorigenesis and screening for potential anti-tumorigenesis mAbs.