Toward a Molecular-Genetic Classification of Spitzoid Neoplasms.

The histopathologic spectrum of Spitzoid neoplasms includes Spitz nevi, atypical Spitz tumors, and Spitzoid melanomas. Advances in molecular genetics have evolved to the point that Spitzoid lesions can now be reasonably classified according to their distinctive molecular-genetic alterations: Spitzoid lesions with (1) 11p amplification and/or HRAS mutations; (2) isolated loss of 6q23 by fluorescence in situ hybridization (FISH); (3) homozygous deletion of 9p21 by FISH; (4) BAP1 loss and BRAFV600 E mutation; (5) translocations involving any of a number of different oncogenic kinase drivers, including ROS1, ALK, NTRK1, NTRK3, MET, BRAF, and RET; and (6) TERT promoter mutations.

Classification of Indeterminate Melanocytic Lesions by MicroRNA Profiling.

PURPOSE: Identification of indeterminate melanocytic skin lesions capable of neoplastic progression is suboptimal and may potentially result in unnecessary morbidity from surgery. MicroRNAs (miRs) may be useful in classifying indeterminate Spitz tumors as having high or low risk for malignant behavior. METHODS: RNA was extracted from paraffin-embedded tissues of benign nevi, benign Spitz tumors, indeterminate Spitz tumors, and Spitzoid melanomas in adults (n = 62) and children (n = 28). The expression profile of 12 miRs in adults (6 miRs in children) was analyzed by real-time polymerase chain reaction. RESULTS: Benign Spitz lesions were characterized by decreased expression of miR-125b and miR-211, and upregulation of miR-22, compared with benign nevi (p < 0.05). A comparison of Spitzoid melanomas to benign nevi revealed overexpression of miR-21, miR-150, and miR-155 in the malignant primaries (p < 0.05). In adults, Spitzoid melanomas exhibited upregulation of miR-21, miR-150, and miR-155 compared with indeterminate Spitz lesions. Indeterminate Spitz lesions with low-risk pathologic features had lower miR-21 and miR-155 expression compared with Spitzoid melanoma tumors in adults (p < 0.05), while pathologic high-risk indeterminate Spitz lesions had increased levels of miR-200c expression compared with low-risk indeterminate lesions (p < 0.05). Pediatric Spitzoid melanomas exhibited increased miR-21 expression compared with indeterminate Spitz lesions (p < 0.05). Moreover, miR-155 expression was increased in indeterminate lesions with mitotic counts >1 and depth of invasion >1 mm, suggesting miR-155 expression is associated with histological characteristics. CONCLUSIONS: miR expression profiles can be measured in indeterminate Spitz tumors and correlate with markers of malignant potential.

The utilization of spitz-related nomenclature in the histological interpretation of cutaneous melanocytic lesions by practicing pathologists: results from the M-Path study.

BACKGROUND: Spitz nevi, atypical Spitz tumors and spitzoid melanomas ('spitzoid lesions') represent controversial and poorly understood cutaneous melanocytic lesions that are difficult to diagnose histologically. It is unknown how these terms are used by pathologists. METHODS: We describe use of Spitz-related terminology using data from the Melanoma Pathology (M-Path) study database comprising pathologists' interpretations of biopsy slides, a nation-wide study evaluating practicing US pathologists' (N = 187) diagnoses of melanocytic lesions (8976 independent diagnostic assessments on 240 total test cases, with 1 slide per case). RESULTS: Most pathologists (90%) used the Spitz-related terminology. However, significant variation exists in which specific lesions were diagnosed as spitzoid and in the corresponding treatment recommendations. Recommendations ranged from 'no further treatment' to 'wide excision of 10 mm or greater' with no category capturing more than 50% of responses. For spitzoid melanoma diagnoses, 90% of pathologists recommended excision with ≥10 mm margin. Pathologists report less confidence in diagnosing these lesions compared with other melanocytic proliferations and are more likely to request second opinions and additional clinical information (all p < 0.05). CONCLUSIONS: Spitzoid lesions are often not classified in any standardized way, evoke uncertainty in diagnosis by pathologists, and elicit variability in treatment recommendations.

Pediatric Melanoma and Atypical Melanocytic Neoplasms.

Melanoma is uncommon in the pediatric age range, but is increasing in frequency and often presents with atypical features compared to the classic ABCDE criteria common to adult melanoma cases. Moreover, many melanocytic neoplasms in childhood pose diagnostic challenges to the pathologist, and sometimes cannot be unequivocally classified as benign nevi or melanoma. This chapter addresses the evaluation and management of pediatric patients with melanoma and atypical melanocytic neoplasms, including the roles of and unresolved questions surrounding sentinel lymph node biopsy, completion lymphadenectomy, adjuvant therapy, and treatment of advanced disease.

Hyperspectral imaging of melanocytic lesions.

Hyperspectral imaging (HSI) allows the identification of objects through the analysis of their unique spectral signatures. Although first developed many years ago for use in terrestrial remote sensing, this technology has more recently been studied for application in the medical field. With preliminary data favoring a role for HSI in distinguishing normal and lesional skin tissues, we sought to investigate the potential use of HSI as a diagnostic aid in the classification of atypical Spitzoid neoplasms, a group of lesions that often leave dermatopathologists bewildered. One hundred and two hematoxylin and eosin-stained tissue samples were divided into 1 of 4 diagnostic categories (Spitz nevus, Spitz nevus with unusual features, atypical Spitzoid neoplasm, and Spitzoid malignant melanoma) and 1 of 2 control groups (benign melanocytic nevus and malignant melanoma). A region of interest was selected from the dermal component of each sample, thereby maximizing the examination of melanocytes. Tissue samples were examined at ×400 magnification using a spectroscopy system interfaced with a light microscope. The absorbance patterns of wavelengths from 385 to 880 nm were measured and then analyzed within and among groups. All tissue groups demonstrated 3 common absorbance spectra at 496, 533, and 838 nm. Each sample group contained at least one absorption point that was unique to that group. The Spitzoid malignant melanoma category had the highest number of total and unique absorption points for any sample group. The data were then clustered into 12 representative spectral classes. Although each of the sample groups contained all 12 spectral vectors, they did so in differing proportions. These preliminary results reveal differences in the spectral signatures of the Spitzoid lesions examined in this study. Further investigation into a role for HSI in classifying atypical Spitzoid neoplasms is encouraged.

Characteristics of spitzoid melanoma and clues for differential diagnosis with spitz nevus.

The different features of spitzoid melanoma are not well characterized in the literature, and the lesion often has to be described in comparison with Spitz nevus. We evaluated the histopathological appearance of spitzoid melanoma by reviewing all spitzoid melanomas treated at our hospital and all referrals from 1998 to 2010. The final study sample comprised 18 cases, 11 from our institution and 7 referrals from other centers. We recorded clinical parameters (eg, age, sex, site, time between onset and excision, recurrence, and death) and a series of histopathological parameters (eg, size, ulceration, symmetry, Clark level, Breslow thickness, cell density, atypia, mitosis). Clinical and histopathological criteria were not available for the 7 referrals. Mean age was 35.2 years (15-56), and 8 patients were women. Mean size of the lesions was 7.27 mm (Clark III/IV and Breslow 2.51 mm), and these were found on the limbs and trunk. Cell density was high in 10 cases and atypia present in 9 (marked in 1). Mitoses were observed in 8 cases (atypical in 4, clusters in 4). Maturation was absent in 9 cases and zonation in 8. Our analysis revealed 5 previously undefined subtypes of spitzoid melanoma (genuine (7 cases), uniform (5 cases), packed (5 cases), polypoid (3 cases) and pigmented (2 cases)]. Four cases showed 2 patterns at the same time. The most useful parameters for the differential diagnosis were cell density, mitosis, zonation, infiltration pattern, and consumption of the epidermis. Assignation of a spitzoid melanoma to 1 of more of our 5 subtypes can enable a more confident diagnosis to be made.

Statistical analysis of the concordance of immunohistochemical stains with the final diagnosis in spitzoid neoplasms.

INTRODUCTION: The classification of spitzoid melanocytic tumors can be difficult, and pathologists rely on both histological features and clinical information to arrive at a diagnosis. We proposed that an immunohistochemical panel could be useful in classifying these neoplasms and designed a study to test the independent contribution of the panel to the final diagnosis. METHODS: We identified 121 cases previously signed out either as (1) Spitz nevus, (2) atypical spitzoid neoplasm, favor Spitz nevus, (3) atypical spitzoid neoplasm of uncertain malignant potential, (4) atypical spitzoid neoplasm, favor melanoma, and (5) spitzoid melanoma. The slides were reveiwed in random order by 4 pathologists. For the first review, the pathologists received only hematoxylin and eosin sections and patient age. Subsequently, the same pathologists interpreted the immunohistochemically stained slides (S-100A6, HMB-45, and MIB-1) on the same cases in randomized order without the benefit of either hematoxylin and eosin sections or patient age. The original diagnosis (based on a combination of clinical information, hematoxylin and eosin-stained sections and immunohistochemical stains) was the gold standard used for statistical analysis. The primary aim of the study was to determine the level of agreement between interpretions based on hematoxylin and eosin sections and age, the immunostains alone, and the gold standard, thus providing a measurement of the degree to which each of these elements contributes to the final diagnosis. The agreement between the gold standard and external review was also determined for those cases sent for external review. RESULTS: The generalized kappa statistic was 0.95 for both the hematoxylin and eosin-stained slides alone and the immunohistochemical stains alone, implying a high level of agreement among the 4 pathologists. The combined weighted kappa statistic for the comparison of hematoxylin and eosin sections and patient age to the gold standard was 0.49, and for the immunohistochemically stained slides to the gold standard 0.48, indicating that a diagnosis based on hematoxylin and eosin sections alone or immunostains alone show only a moderate and similar level of agreement with the gold standard diagnosis. Only the most controversial cases were sent for external review. The weighted kappa statistic estimate was 0.30 for the gold standard diagnosis on those cases and the external review. CONCLUSIONS: Spitzoid neoplasms remain a difficult area in dermatopathology and experts frequently disagree on the most challenging cases. An immunohistochemical panel contributes to the diagnosis of spitzoid tumors, and the contribution is statistically similar to that of hematoxylin and eosin sections and age. Interpretation remains subjective, as evidenced by the comparison of the gold standard and external review.

Melanocytic tumors of uncertain malignant potential: results of a tutorial held at the XXIX Symposium of the International Society of Dermatopathology in Graz, October 2008.

Several reports demonstrated the difficulties and lack of agreement in the histopathologic diagnosis of particular melanocytic tumors (atypical Spitz tumors, atypical blue nevi, deep penetrating nevi). These lesions are often referred to as "melanocytic tumors of uncertain malignant potential" (MELTUMP). We studied a large number of such tumors to find out whether repeatable histopathologic criteria for distinction of benign from malignant cases exist. Fifty-seven cases of MELTUMP were classified within 3 groups according to behavior as follows: (a) favorable (no evidence of metastatic disease after a follow-up of > or = 5 y), (b) unfavorable (tumor-related death and/or large metastatic deposits in the lymph nodes and/or visceral metastases), (c) borderline (small nodal deposits of tumor cells < or = 0.2 mm). There were no significant differences in tumor thickness and presence or absence of ulceration between the different groups. The only 3 histopathologic criteria that were statistically different between the groups of favorable and unfavorable cases were presence of mitoses, mitoses near the base, and an inflammatory reaction, all of them found more frequently in cases with unfavorable behavior. The major outcome of this study of a series of "MELTUMPs" suggests as a preliminary observation that these lesions as a group exist and that they may be biologically different from conventional melanoma and benign melanocytic nevi. The terminology remains highly controversial, reflecting the uncertainty in classification and interpretation of these atypical melanocytic tumors.

State of the art, nomenclature, and points of consensus and controversy concerning benign melanocytic lesions: outcome of an international workshop.

The following communication summarizes the proceedings of a one-day International Workshop focusing on the histology of benign melanocytic nevi. Areas of controversy identified in 6 focus sessions were the nomenclature and relationships among common nevi including nevi with halo reactions, traumatized nevi, "dysplastic" nevi, and nevi from particular anatomic sites; developmental biology and frequency of malignant transformation associated with congenital nevi; the characterization and biologic nature of atypical spitzoid neoplasms; the basic definition of particular melanocytic cellular phenotypes, and the nomenclature and biologic nature of many candidate blue nevi, combined nevi, and other controversial lesions such as deep penetrating nevus and pigmented epithelioid melanocytoma. Concentrated data collection and follow-up, molecular characterization, and future consensus Workshops may facilitate the resolution of some of these problems. The Group recommended the description of ambiguous or "borderline" lesions as tumors with indeterminate or uncertain biologic/malignant potential. The participants also advised that such lesions at a minimum should be managed by complete excision with clear surgical margins.

Loss of expression of protein kinase a regulatory subunit 1alpha in pigmented epithelioid melanocytoma but not in melanoma or other melanocytic lesions.

Pigmented epithelioid melanocytoma (PEM) is a recently described entity comprising most cases previously described as "animal-type melanoma" and epithelioid blue nevus (EBN) occurring in patients with the multiple neoplasia syndrome Carney complex (CNC). Mutations of the protein kinase A regulatory subunit type 1alpha (R1alpha) (coded by the PRKAR1A gene) are found in more than half of CNC patients. In this study, we investigated whether PEM and EBN are related at the molecular level, and whether changes in the PRKAR1A gene status and the expression of the R1alpha protein may be involved in the pathogenesis of PEM and other melanocytic lesions. Histologic analysis of hematoxylin and eosin-stained sections and immunohistochemistry (IHC) with R1alpha antibody were performed on 34 sporadic PEMs, 8 CNC-associated PEMs from patients with known PRKAR1A mutations, 297 benign and malignant melanocytic tumors (127 conventional sections of 10 compound nevi, 10 Spitz nevi, 5 deep-penetrating nevi, 5 blue nevi, 6 cellular blue nevi, 2 malignant blue nevi, 3 lentigo maligna, and 86 melanomas of various types); in addition, 170 tissue microarray sections consisting of 35 benign nevi, 60 primary melanomas, and 75 metastatic melanomas, and 5 equine dermal melanomas, were examined. Histologic diagnoses were based on preexisting pathologic reports and were confirmed for this study. DNA studies [loss of heterozygosity (LOH) for the 17q22-24 locus and the PRKAR1A gene sequencing] were performed on 60 melanomas and 7 PEMs. IHC showed that R1alpha was expressed in all but one core from tissue microarrays (169/170), and in all 127 melanocytic lesions evaluated in conventional sections. By contrast, R1alpha was not expressed in the 8 EBN from patients with CNC and PRKAR1A mutations. Expression of R1alpha was lost in 28 of 34 PEMs (82%). R1alpha was expressed in the 5 equine melanomas studied. DNA studies correlated with IHC findings: there were no PRKAR1A mutations in any of the melanomas studied and the rate of LOH for 17q22-24 was less than 7%; 5 of the 7 PEMs showed extensive 17q22-24 LOH but no PRKAR1A mutations. The results support the concept that PEM is a distinct melanocytic tumor occurring in a sporadic setting and in the context of CNC. They also suggest that PEM differs from melanomas in equine melanotic disease, further arguing that the term animal-type melanoma may be a misnomer for this group of lesions. Loss of expression of R1alpha offers a useful diagnostic test that helps to distinguish PEM from lesions that mimic it histologically.