On the nature of histologic observations: the case of the Spitz nevus

Spitz Tumors and Melanoma in the Genomic Age: A Retrospective Look at Ackerman's Conundrum

After 25 years, "Ackerman's conundrum", namely, the distinction of benign from malignant Spitz neoplasms, remains challenging. Genomic studies have shown that most Spitz tumors harbor tyrosine and serine/threonine kinase fusions, including ALK, ROS1, NTRK1, NTRK2, NTRK3, BRAF and MAP3K8, or some mutations, such as HRAS and MAP3K8. These chromosomal abnormalities act as drivers, initiating the oncogenetic process and conferring basic bio-morphological features. Most Spitz tumors show no additional genomic alterations or few ones; others harbor a variable number of mutations, capable of conferring characteristics related to clinical behavior, including CDKN2A deletion and TERT-p mutation. Since the accumulation of mutations is gradual and progressive, tumors appear to form a bio-morphologic spectrum, in which they show a progressive increase of clinical risk and histological atypia. In this context, a binary classification Spitz nevus-melanoma appears as no longer adequate, not corresponding to the real genomic substrate of lesions. A ternary classification Spitz nevus-Spitz melanocytoma-Spitz melanoma is more adherent to the real neoplastic pathway, but some cases with intermediate ambiguous features remain difficult to diagnose. A prognostic stratification of Spitz tumors, based on the morphologic and genomic characteristics, as a complement to the diagnosis, may contribute to better treatment plans for patients.

Conceptual Evolution and Current Approach to Spitz Tumors

Over the past several decades, the study of Spitz neoplasms has flourished, with expanded conceptualization and refined terminology, providing a framework for the assessment and classification of Spitz nevi, atypical Spitz Tumors, and Spitz melanoma. Cancer genomics have generated concepts such as driver and passenger genes and clonal evolution, which can be applied to Spitz tumors. Herein, we provide a historical perspective, followed by a summary of current knowledge and clinical approaches for these challenging tumors.

Impact of Next-generation Sequencing on Interobserver Agreement and Diagnosis of Spitzoid Neoplasms

Atypical Spitzoid melanocytic tumors are diagnostically challenging. Many studies have suggested various genomic markers to improve classification and prognostication. We aimed to assess whether next-generation sequencing studies using the Tempus xO assay assessing mutations in 1711 cancer-related genes and performing whole transcriptome mRNA sequencing for structural alterations could improve diagnostic agreement and accuracy in assessing neoplasms with Spitzoid histologic features. Twenty expert pathologists were asked to review 70 consultation level cases with Spitzoid features, once with limited clinical information and again with additional genomic information. There was an improvement in overall agreement with additional genomic information. Most significantly, there was increase in agreement of the diagnosis of conventional melanoma from moderate (κ=0.470, SE=0.0105) to substantial (κ=0.645, SE=0.0143) as measured by an average Cohen κ. Clinical follow-up was available in all 70 cases which substantiated that the improved agreement was clinically significant. Among 3 patients with distant metastatic disease, there was a highly significant increase in diagnostic recognition of the cases as conventional melanoma with genomics (P<0.005). In one case, none of 20 pathologists recognized a tumor with BRAF and TERT promoter mutations associated with fatal outcome as a conventional melanoma when only limited clinical information was provided, whereas 60% of pathologists correctly diagnosed this case when genomic information was also available. There was also a significant improvement in agreement of which lesions should be classified in the Spitz category/WHO Pathway from an average Cohen κ of 0.360 (SE=0.00921) to 0.607 (SE=0.0232) with genomics.

Molecular profiling of Spitz nevi identified by digital RNA counting

Supplemental Digital Content is available in the text.

The molecular properties of benign melanocytic lesions are poorly understood. Only a few studies have been carried out on specific nevi subtypes, including common nevocellular nevi (NCN) or Spitz nevi (SN). Genomic alterations in melanoma-associated oncogenes are typically absent in SN. In the present study, mRNA expressions of 25 SN and 15 NCN were analyzed. Molecular profiling was performed using the RNA NanoString nCounter Gene Expression Platform (number of genes=770). Marker discovery was performed with a training set consisting of seven SN and seven NCN samples from the same patients, and validation was performed using a second set consisting of 18 SN and eight NCN samples. Using the training set, 197 differentially expressed genes were identified in SN versus NCN. Of these, 74 genes were validated in the validation set (false discovery rate q≤0.13). In addition, using random forest and least absolute shrinkage and selection operator feature selection, a molecular signature of SN versus NCN was identified including 15 top-ranked genes. The present study identified a distinct molecular expression profile in SN compared with NCN, even when lesions were obtained from the same patients. Gene set analysis showed upregulation of gene pathways with increased expression of transcripts related to immunomodulatory, inflammatory, and extracellular matrix interactions as well as angiogenesis-associated processes in SN. These findings strongly indicate that SN represent a distinct group of melanocytic neoplasms and evolve differentially and not sequentially from NCN.

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.

Spitz Nevi and Other Spitzoid Neoplasms in Children: Overview of Incidence Data and Diagnostic Criteria

Spitz nevi are benign melanocytic neoplasms characterized by epithelioid or spindle melanocytes or both. In some rare cases their presentation overlaps with the clinical and histopathologic features of malignant melanoma, so a differential diagnosis can be difficult to make. Intermediate forms between Spitz nevi and malignant melanoma, with unpredictable behavior, have been called atypical Spitz tumors. A literature search was performed to review the clinical, dermoscopic, genetic, and histopathologic aspects of spitzoid tumors. Spitz nevi mainly occur in children, with no predilection for sex, and in young women. Common sites are the head and lower arms, where Spitz nevi present as pink nodules or hyperpigmented plaques. Spitzoid lesions may have diverse dermoscopic patterns: vascular, starburst, globular, atypical, reticular, negative homogeneous, or targetoid. The management of spitzoid lesions can be invasive or conservative; surgical excision is usually reserved for those with doubtful features, whereas clinical and dermoscopic follow-up is preferred for typical pediatric Spitz nevi. The role of sentinel lymph node biopsy in atypical Spitz tumors is debated. Immunohistochemistry and new molecular techniques such as comparative genomic hybridization, polymerase chain reaction, and fluorescence in situ hybridization offer new diagnostic perspectives, investigating genetic alterations that are specific for malignant melanoma or for Spitz nevi.

Variation among pathologists' treatment suggestions for melanocytic lesions: A survey of pathologists

BACKGROUND

The extent of variability in treatment suggestions for melanocytic lesions made by pathologists is unknown.

OBJECTIVE

We investigated how often pathologists rendered suggestions, reasons for providing suggestions, and concordance with national guidelines.

METHODS

We conducted a cross-sectional survey of pathologists. Data included physician characteristics, experience, and treatment recommendation practices.

RESULTS

Of 301 pathologists, 207 (69%) from 10 states (California, Connecticut, Hawaii, Iowa, Kentucky, Louisiana, New Jersey, New Mexico, Utah, and Washington) enrolled. In all, 15% and 7% reported never and always including suggestions, respectively. Reasons for offering suggestions included improved care (79%), clarification (68%), and legal liability (39%). Reasons for not offering suggestions included referring physician preference (48%), lack of clinical information (44%), and expertise (29%). Training and caseload were associated with offering suggestions (P < .05). Physician suggestions were most consistent for mild/moderate dysplastic nevi and melanoma. For melanoma in situ, 18 (9%) and 32 (15%) pathologists made suggestions that undertreated or overtreated lesions based on National Comprehensive Cancer Network (NCCN) guidelines, respectively. For invasive melanoma, 14 (7%) pathologists made treatment suggestions that undertreated lesions based on NCCN guidelines.

LIMITATIONS

Treatment suggestions were self-reported.

CONCLUSIONS

Pathologists made recommendations ranging in consistency. These findings may inform efforts to reduce treatment variability and optimize patterns of care delivery for patients.

FTIR microspectroscopic characterization of Spitz nevi

In the last 10 years, few efforts have been carried out to apply vibrational spectroscopy in the study of dermal pathologies in order to characterize the most relevant spectral markers for distinguishing benign from cancerous lesions. Spitz nevi are a special group of benign melanocytic lesions, characterized by spindled and/or epithelioid nevomelanocytes, with peculiar clinical, dermoscopic and histopathological features. The "atypical forms" of Spitz nevi are among the commonest problems of differential diagnosis with the so-called "spitzoid melanomas". The clinical and histological criteria for discriminating these two entities are very subtle and often still quite subjective, and, in a significant percentage of cases, can lead to diagnostic pitfalls and inadequate therapies. Therefore, it is noteworthy to outline that the diagnosis of melanocytic lesions still represents a challenging problem and a continue matter of discussion. We exploited FTIR microspectroscopy to study the different kinds of spitzoid melanocytes, in order to define the most relevant spectral markers of each specimen and to achieve objective information on "borderline" histologically atypical lesions. In particular, the spectroscopic investigation was carried out on melanocytes deriving from normal skin (as a normal control), malignant melanoma and Spitz nevi. The presence of the characteristic bands of melanin was investigated, too.

The MPATH-Dx reporting schema for melanocytic proliferations and melanoma

BACKGROUND

The histologic diagnosis of melanoma and nevi can be subject to discordance and errors, potentially leading to inappropriate treatment and harm. Diagnostic terminology is not standardized, creating confusion for providers and patients and challenges for investigators.

OBJECTIVE

We sought to describe the development of a pathology reporting form for more precise research on melanoma and a diagnostic-treatment mapping tool for improved patient care and consistency in treatment.

METHODS

Three dermatopathologists independently reviewed melanocytic lesions randomly selected from a dermatopathology database. Melanocytic Pathology Assessment Tool and Hierarchy for Diagnosis (MPATH-Dx) reporting schema evolved from iterative case review and form revision.

RESULTS

Differences in diagnostic thresholds, interpretation, and nomenclature contributed to development of the MPATH-Dx histology reporting form, which groups lesions by similarities in histogenesis and degrees of atypia. Because preliminary results indicate greater agreement regarding suggested treatments than for specific diagnoses, the diverse terminologies of the MPATH-Dx histology reporting form were stratified by commonalities of treatments in the MPATH-Dx diagnostic-treatment mapping scheme.

LIMITATIONS

Without transformative advances in diagnostic paradigms, the interpretation of melanocytic lesions frequently remains subjective.

CONCLUSIONS

The MPATH-Dx diagnostic-treatment mapping scheme could diminish confusion for those receiving reports by categorizing diverse nomenclature into a hierarchy stratified by suggested management interventions.

Spitz nevus and Reed nevus

Spitz and Reed nevi, also called spindle and/or epithelioid cell nevi, are a special group of melanocytic lesions due to their peculiar clinical, dermoscopic and histopathological features. The study of these nevi is of great interest because both their nomenclature and classification are still a matter of discussion. Most importantly, the difficulty to differentiate them from melanoma can lead to inadequate therapies. In this context, dermoscopy, a link between clinical and anatomopathological examinations, appears as a helpful diagnostic tool whose accuracy can reach 93%. "Borderline" lesions are still a great challenge and object of research, including molecular studies. The present study explores the relevant characteristics of these nevi, with emphasis on dermoscopic findings, aiming at understanding their natural history, as well as discussing treatment and patient follow-up.

Spitz nevi and other Spitzoid lesions part I. Background and diagnoses

Spitz nevi are melanocytic proliferations that are characterized by spindled and/or epithelioid nevomelanocytes. First interpreted as juvenile melanoma, these lesions were later characterized as benign and were observed to affect all age groups. Today, contrasting opinions persist regarding the fundamental benignancy versus malignancy within the spectrum of Spitz tumors. Beyond clinical outcome, this controversy has also been fueled by complex and sometimes convoluted classification schemes based on pathologic characteristics. More recently, immunophenotypic and molecular analyses have begun to clarify the etiologic nature of these tumors. Recent evidence suggests that histopathologic features that suggest more aggressiveness in Spitz tumors relate to mitoses and inflammation.

An unusual presentation of spitz lesion on an adolescent's foot

The authors present a case of spitzoid nevus of the left fourth toe in a 16-year-old boy, which was confirmed by biopsy to be a Spitz nevus. In a young individual, we feel that it is important to maintain a high index of suspicion for an atypical lesion that displays unusual physical findings. Spitz nevus is an infrequent, acquired melanocytic nevus composed of epithelial and spindle melanocytes that is difficult to differentiate from a melanoma. Presently, there are no immunohistochemical markers or molecular biologic techniques that can be used to make a completely certain diagnosis of Spitz nevus versus melanoma. Spitz tumors are most commonly located on the lower extremities in children. Treatment of the lesion is typically carried out by means of excision.

The immunohistochemical profile of Spitz nevi and conventional (non-Spitzoid) melanomas: a baseline study

Several isolated markers have been proposed to aid in differential diagnostic of difficult melanocytic lesions, albeit none has been shown to be definitive in differentiating Spitz nevus from melanoma. This study proposes a wide panel of 22 markers having important functions in different biological functions (cell cycle, apoptosis, DNA repair proteins and membranous receptors) to provide a combination of proteins associated with either benign or malignant phenotype. Using tissue microarrays, we compared protein expression profiles in 28 typical Spitz nevi and 62 primary vertical growth phase non-spitzoid melanomas. Most of the significant differences were linked to cell-cycle deregulation such as overexpression of cyclin D1 and p21 in Spitz nevi compared with non-spitzoid melanomas (74 vs 16% and 91 vs 27%, respectively) and mitotic rate including Ki-67, highly expressed in deep areas of non-spitzoid melanomas (37%), whereas it is not expressed in Spitz nevi (0%), topoisomerase IIalpha (79% in non-spitzoid melanomas vs 15% in Spitz nevi) and nuclear survivin (69% in melanomas vs 0% in Spitz nevi). A combination of biological markers differentially expressed in Spitz nevi from non-spitzoid melanomas is defined, thus providing a potential tool for histopathological differential diagnostic between Spitz nevus and melanoma. Nevertheless, more studies including atypical Spitz nevi and spitzoid melanomas are necessary to further establish a reliable panel to differentiate among difficult cases.

The Spitzoid lesion: rethinking Spitz tumors, atypical variants, 'Spitzoid melanoma' and risk assessment

Although much remains to be learned about Spitzoid lesions, there is increasing evidence that these tumors may be a type of melanocytic neoplasm distinct from conventional melanocytic nevi and malignant melanoma. In the current communication, the author has attempted to describe accurately the state-of-the-art surrounding these lesions, their nomenclature, and assessment of risk. Acknowledging the peculiar nature of Spitzoid lesions, the author prefers the term Spitz tumor rather than 'Spitz nevus' (except perhaps for the most typical lesions) and argues against using the term 'Spitzoid melanoma' until more information is available to justify such a term. The author also believes that patients are best served by the comprehensive evaluation of Spitzoid lesions and their classification into three categories: (1) Spitz tumor without significant abnormality, (2) Spitz tumor with one or more atypical features (atypical Spitz tumor), including those judged to have indeterminate biological potential, and (3) malignant melanoma, rather than the two categories of 'Spitz nevus' and melanoma. Only rigorous characterization of sufficient numbers of Spitzoid lesions and long-term follow-up of patients will provide truly objective information for the formulation of optimal guidelines for the management of patients with these lesions.

High-risk surgically resected pediatric melanoma and adjuvant interferon therapy

BACKGROUND

Pediatric patients with high-risk surgically resected melanoma are at risk for relapse, yet little is known about these young patients and how they tolerate high-dose interferon therapy.

PROCEDURE

We reviewed medical records of patients (< or =18 years) with high-risk melanoma referred to the University of Michigan Pediatric Hematology-Oncology service between January 1989 and July 2003.

RESULTS

Fourteen patients were identified with high-risk resected melanoma. The median age at diagnosis was 8.5 years. The median time to establish diagnosis was 9 months. Primary lesions were diagnosed as unequivocal melanoma, atypical epithelioid melanocytic proliferations, or atypical Spitz tumor with indeterminate malignant potential. Twelve patients had a positive sentinel lymph node (SLN) biopsy or a palpable regional lymph node and underwent regional lymph node dissection (LND). Two patients with unequivocal melanoma with Breslow depth >4 mm had negative SLN biopsies. Twelve patients received adjuvant high-dose interferon. The following toxicities were observed: constitutional symptoms, gastrointestinal symptoms, depression or neuropsychiatric symptoms, myelosuppression, elevated AST or ALT, hypothyroidism, and hypertension. Grade 3 or 4 toxicities were uncommon with exception of neutropenia, resulting in modification of therapy in one patient. All patients are alive and free of disease at follow-up (median 24.5 months).

CONCLUSIONS

Invasive melanoma can occur in very young children. Despite early signs of malignancy, there is often a delay in diagnosis. Histologically, diagnosis may be difficult because of overlap with Spitz nevi. Pediatric patients tolerated adjuvant high-dose interferon well and may be less likely than adults to require therapy modification secondary to toxicities.

In vivo confocal scanning laser microscopy of pigmented Spitz nevi: Comparison of in vivo confocal images with dermoscopy and routine histopathology

BACKGROUND

Spitz nevus is a benign melanocytic lesion sometimes mistakenly diagnosed clinically as melanoma.

OBJECTIVE

Our aim was to evaluate in vivo reflectance-mode confocal scanning laser microscopy (CSLM) aspects of globular Spitz nevi and to correlate them with those of surface microscopy and histopathology.

METHODS

A total of 6 Spitz nevi, with globular aspects on epiluminescence observation, were imaged with CSLM and subsequently excised for histopathologic examination.

RESULTS

A close correlation among CSLM, epiluminescence, and histopathologic aspects was observed. Individual cells, observed in high-resolution confocal images, were similar in shape and dimension to the histopathologic ones. Lesion architecture was described on reconstructed CSLM images. Melanocytic nests corresponded to globular cellular aggregates at confocal microscopy and to globules at epiluminescence observation. Melanophages were clearly identified in the papillary dermis both by confocal microscopy and histopathology.

CONCLUSION

In vivo CSLM enabled the identification of characteristic cytologic and architectural aspects of Spitz nevi, correlated with histopathology and epiluminescence microscopy observation.

Lumps and bumps in children-when to worry: recent trends in recognition and pathology of hemangiomas of infancy and Spitz nevi

PURPOSE OF REVIEW

Hemangiomas are common, and most lesions are benign. Careful attention needs to be paid to these lesions; however, because their growth can be unpredictable, they can have important complications and can serve as markers of underlying malformations. The consequences of hemangiomas are extensive and can be challenging to recognize.

RECENT FINDINGS

Recent knowledge of the pathogenesis and diagnosis of these lesions has helped raise awareness of their classification and clinical significance. Spitz nevi can also be a challenging lesion to diagnose and treat, although for different reasons. These are lesions composed of melanocytes with clinical and histopathological findings that we easily misdiagnosed and can have significant implications for patient care.

SUMMARY

Both of these important lesions in infants and children are reviewed in further detail with particular attention to recent trends.

Sentinel lymph node biopsy for patients with problematic spitzoid melanocytic lesions: a report on 18 patients

BACKGROUND

Spindle and/or epithelioid melanocytic proliferations that display overlapping histopathologic features of Spitz nevus and Spitz-like melanoma are diagnostically difficult and controversial melanocytic tumors. There are reports of such lesions metastasizing to regional lymph nodes, with a few widely disseminating, resulting in death.

METHODS

The authors reviewed clinical and histopathologic data on all patients with atypical or borderline spitzoid melanocytic proliferations who underwent sentinel lymph node biopsy (SLNB). They examined how frequently histologically problematic or borderline spitzoid melanocytic lesions metastasized to sentinel lymph nodes (SLNs) and which clinical or histologic features, if any, predisposed patients to a higher risk lesion.

RESULTS

Six male patients and 12 female patients, ages 5-32 years (mean, 16 years), had tumors ranging in size from 1.2 mm to 7.9 mm (mean, 3.5 mm) in thickness. Atypical histologic features that were present most frequently included incomplete maturation (18 of 18 patients), deep dermal mitoses (16 of 18 patients), nuclear pleomorphism (10 of 18 patients), and focal sheet-like growth (10 of 18 patients). Eight of 18 patients (44%) had SLN metastasis and were offered adjuvant treatment. One of eight patients with SLN positive results who underwent regional lymphadenectomy had one additional involved lymph node. All 18 patients were alive and well with no evidence of recurrent or metastatic disease after a follow-up of 3-42 months (mean, 12 months).

CONCLUSIONS

Histologically atypical or borderline spitzoid, melanocytic tumors are diagnostically challenging and controversial melanocytic lesions, some of which represent unrecognized melanomas. SLNB aids in confirming a diagnosis of melanoma and identifies patients who may benefit from early therapeutic lymph node dissection and/or adjuvant therapy.

Two cases of unusual acral melanocytic tumors: illustration of molecular cytogenetics as a diagnostic tool

The differential diagnosis between benign Spitz nevus and malignant melanoma may present considerable difficulties in some cases. Here we report 2 unusual melanocytic tumors with spitzoid features developing in acral sites of Japanese patients to illustrate the use of comparative genomic hybridization (CGH) to classify these lesions. Case 1 was a 12-mm-thick, >2 cm-diameter nodule on the sole of a 37-year-old man. Case 2 was a subungual tumor of the left index finger in a 13-year-old boy. CGH showed absence of chromosomal aberrations in case 1 and multiple aberrations in case 2, including focused amplification as previously described in acral melanomas. Case 1 was free of disease after 2.5 years of follow-up, whereas case 2 developed lymph node metastasis. We conclude that molecular techniques such as CGH can be of diagnostic help in the classification of histologically ambiguous lesions.

Molecular cytogenetics as a diagnostic tool for typing melanocytic tumors

The melanocyte can give rise to a variety of both benign and malignant lesions that differ in their clinical and histopathological appearance. It is likely that genetic changes underlie this phenotypic diversity. Comparative genomic hybridization (CGH) is a genome-wide scanning technique that permits the measurement of copy number aberrations in archival tumors. Using CGH, we have demonstrated significant differences in the frequency of chromosomal aberrations in primary cutaneous melanomas and Spitz nevi. Whereas the majority of melanomas have aberrations frequently involving chromosomes 9, 10, 7, and 6, most Spitz nevi do not show aberrations. However, a small subset of Spitz nevi show an isolated gain of the short arm of chromosome 11p. As this aberration has not been observed in melanomas, the measurement of chromosomal aberrations should be further evaluated as a diagnostic tool for ambiguous melanocytic tumors.

The surgical management of Spitz nevi

BACKGROUND

The biologic behavior of Spitz nevi and atypical Spitz nevi ranges from completely benign to the rare malignant melanoma. Various recommendations for the surgical approach to these lesions have been proposed.

OBJECTIVE

To determine any trend in the surgical management of Spitz nevi and atypical Spitz nevi among a community of dermatologists.

METHODS

Retrospective review of the clinical features, surgical management and outcome of 89 patients with the diagnosis of Spitz nevus or atypical Spitz nevus.

RESULTS

All biopsy techniques had a high incidence of involved margins: shave (67%), excision (28%), and punch (21%). Of the atypical Spitz nevi with positive margins on biopsy, there was a trend (7/9) toward reexcision with narrow margins (average 2.2 mm).

CONCLUSION

The majority of atypical Spitz nevi incompletely removed by biopsy were excised with narrow uncontrolled margins. A stratified surgical approach depending on the clinical and histopathologic features of the Spitz lesion is proposed. More aggressive surgical management of Spitz lesions with atypical features may be warranted. Further studies to determine the biologic potential of these lesions are needed.

Management of Spitz nevi: a survey of dermatologists in the United States

BACKGROUND

There is no consensus concerning management of Spitz nevi.

OBJECTIVE

This study was carried out to ascertain how dermatologists manage Spitz nevi.

METHODS

A questionnaire was sent to 997 fellows of the American Academy of Dermatology, 284 pediatric dermatologists, and 27 directors of pigmented-lesion clinics. The results are based on the 381 questionnaires returned.

RESULTS

The vast majority of responding dermatologists (93%) recommend biopsies of suspected Spitz nevi. Of this group, 43% recommend total biopsies and 55% recommend partial biopsies; 2% would recommend either total or partial biopsies, depending on the clinical situation. Sixty-nine percent of physicians would completely excise a lesion that was histologically diagnosed as an incompletely removed Spitz nevus. Seventy percent of general dermatologists and 80% of pediatric dermatologists would recommend excision with a 1- to 2-mm margin of normal-appearing skin around a Spitz nevus. Nine percent of general dermatologists would recommend margins of 4 mm or more; however, all pediatric dermatologists surveyed would recommend margins less than 4 mm. Physicians were less likely to monitor patients whose Spitz nevi were completely removed. Three fourths (74%) of respondents believe Spitz nevi are entirely benign, 4% believe they are precursors to melanoma, and 22% are not sure. Seven percent of general dermatologists and 4% of pediatric dermatologists have seen metastatic melanomas arise at sites of lesions initially diagnosed histologically as Spitz nevi; 40% of pigmented-lesion clinic directors have seen such lesions.

CONCLUSIONS

We believe that the lack of consensus, both in our survey and in the medical literature, reflects to some extent the lack of certainty in the histologic differentiation of Spitz nevi from melanomas and that concern about melanoma influences management. At the pigmented-lesion clinic of the New York University Skin and Cancer Unit, because of this concern about melanoma, it is usually recommended that Spitz nevi be completely excised.

Spitz naevus versus Spitzoid melanoma: when and how can they be distinguished?

Spitz naevus is a benign melanocytic lesion that shares many histological features with melanoma. While Spitz naevi characteristically occur in children and young adults and melanomas in the middle-aged and elderly, either tumour can occur in patients of any age. In many cases, the histopathological diagnosis of Spitz naevus is straightforward, particularly in small lesions displaying many or all of the typical histological features and occurring in young patients. Tumours that deviate from the classic description, however, cause difficulties in diagnosis. In this review, we highlight histopathological features of Spitz naevi and those that may be useful in distinguishing Spitz naevi from melanomas. We find that the presence of good symmetry, Kamino bodies, and uniformity of cell nests or sheets from side-to-side favours a Spitz naevus. The presence of abnormal mitoses, a dermal mitotic rate of >2/mm2, and mitotic figures within 0.25 mm of the deep border of the lesion favours a melanoma. Immunohistochemical stains for HMB45 and Ki67 sometimes provide additional useful information. Despite this, in some cases it may not be possible to give an unequivocal diagnosis. Recommendations for the reporting of such cases are provided. New techniques have also demonstrated chromosomal, molecular and genetic differences between Spitz naevi and melanomas. This report highlights these new data and speculates on their possible future role in the diagnosis of borderline lesions.

Spitzoid malignant melanoma in teenagers: an entity with no better prognosis than that of other forms of melanoma

AIMS

A rare form of melanoma in teenagers closely simulates Spitz naevus and is claimed to have a good prognosis. The aim of this study is to identify the clues for a confident diagnosis of this entity and to confirm the peculiarly good prognosis.

METHODS AND RESULTS

Two cases of melanoma with Spitzoid features were compared with Spitz naevus and it was found that the major distinctive criteria are: mitoses and single cell necrosis in the deepest part of the lesion, cellular and particularly nuclear and nucleolar pleomorphism, and growth pattern in solid sheets of cells. More subtle clues were the asymmetric distribution of pigment and the thinning of the epidermis with parakeratosis and exudate in the cornified layer. Both of the lesions reached the mid-dermis. There was a fatal outcome in both patients after generalized metastatic spread. The metastatic disease in one of the cases appeared 15 years after the excision of the primary lesion.

CONCLUSIONS

Spitzoid melanoma in teenagers can be distinguished from Spitz naevus if strict criteria are followed. Spitzoid melanoma does not show a better prognosis than other types of melanoma if the follow-up is prolonged enough.

Mutations and copy number increase of HRAS in Spitz nevi with distinctive histopathological features

Spitz nevus is a benign melanocytic neoplasm that can be difficult or impossible to histologically distinguish from melanoma. We have recently described copy number increases of chromosome 11p in a subset of Spitz nevi. To study the molecular and histological features of this group, we studied 102 Spitz nevi for 11p copy number increases using fluorescence in situ hybridization (FISH) on tissue arrays. Copy number increases of at least threefold were found in 12 cases (11.8%) and involved the HRAS gene on chromosome 11p. Sequence analysis of HRAS showed frequent oncogenic mutations in cases with copy number increase (8/12 or 67%), contrasting with rare HRAS mutations in cases with normal HRAS copy numbers (1/21 or 5%, P: < 0.0001). Tumors with 11p copy number increases were larger, predominantly intradermal, had marked desmoplasia, characteristic cytological features, and had an infiltrating growth pattern. Proliferation rates in the majority of these cases were low to absent. HRAS activation by either mutation or copy number increase alone could explain several of the histological features that overlap with those of melanoma. We speculate that HRAS activation in the absence of co-operating additional genetic alterations drives the partially transformed melanocytes of these Spitz nevi into senescence or a stable growth arrest. Although there is no data suggesting that Spitz nevi with HRAS activation are at risk for progression to melanoma, future studies are warranted to assess their biological behavior more accurately.

Problematic pigmented lesions: approach to diagnosis

A number of pigmented lesions are difficult to classify and raise the possibility of a melanoma diagnosis. Care should be exercised to exclude non-melanocytic lesions, and benign melanocytic entities, both of which can mimic melanoma histologically. In addition, the possibility of the lesion being a melanoma variant or epidermotropic metastasis should be considered. There will still be some cases that are difficult to resolve. These usually fall into one of three categories: atypical junctional melanocytic lesion versus early melanoma; naevus versus naevoid melanoma; and atypical Spitz, cellular blue, and deep penetrating naevi versus thick melanoma. These will pose problems even for experts. The atypical Spitz lesions are perhaps the most important category because they tend to be from younger individuals, the differential diagnosis is thick melanoma, and there is no single discriminating histological feature.

Recent developments in the pathology of melanocytic neoplasia

This article selectively discusses clinically relevant aspects of the pathology of cutaneous melanocytic neoplasms, from the literature of the past recent years. Topics include the changing role of immunohistochemistry in diagnosis, the controversies over dysplastic nevi, description of other specialized variants of melanocytic nevi, diagnosis of melanocytic neoplasms of acral skin, and melanoma occurring in childhood. Several variants of melanoma including desmoplastic and spindle-cell types, verrucous melanoma, epidermotropic melanoma, and melanoma of the female genitalia are reviewed. The issue of appropriate margins of resection for melanoma and the use of Mohs Micrographic surgery for this tumor are considered. Finally, a review of the sentinel node biopsy technique and of nodal nevi is presented.

Atypical Spitz nevi/tumors: lack of consensus for diagnosis, discrimination from melanoma, and prediction of outcome

The biological nature of Spitz nevi/tumors and their diagnostic distinction from, or relationship to, melanoma remain unresolved issues. In this report, a series of 30 melanocytic lesions removed from 28 patients, including atypical Spitz nevi/tumors and metastasizing Spitzoid tumors/melanomas, were evaluated by a panel of dermatopathologists to evaluate interobserver diagnostic concordance and to assess the prognostic power of histological criteria. For inclusion in the study, each lesion had to display some criteria for the Spitz nevus, and in addition one of the following was required: (1) definitive clinical outcome such as metastasis or death of disease, or (2) long-term follow-up if the patient remained disease free. Each lesion was reviewed independently and blinded as to the clinical data by 10 pathologists, who categorized them as (1) typical Spitz nevus/tumor, (2) atypical Spitz nevus/tumor, (3) melanoma, (4) tumor with unknown biological potential, or (5) other melanocytic lesion. There was limited discussion of criteria before the review. Evaluation of 17 Spitzoid lesions yielded no clear consensus as to diagnosis; in only one case did six or more pathologists agree on a single category, regardless of clinical outcome. Notably, however, some lesions that proved fatal were categorized by most observers as either Spitz nevi or atypical Spitz tumors. Conversely, seven or more pathologists scored 13 lesions as melanoma. These results illustrate (1) substantial diagnostic difficulties posed by many Spitz tumors, especially those with atypical features, even among experts, and (2) the lack of objective criteria for their distinction from melanoma and for gauging their malignant potential. Nevertheless, our observations do suggest that a biological relationship exists between the Spitz nevus/tumor and melanoma.

Spitz nevus or melanoma?

Spitz nevi are benign melanocytic neoplasms of children and young adults that can be exceedingly difficult to distinguish from malignant melanomas. Although a nearly definite diagnosis can be made in most cases, the histological distinction between Spitz nevi and melanomas is equivocal in about 6% to 8% of cases. In those cases, and perhaps even with presumed benign Spitz nevi, clear surgical margins are desirable. The most helpful differentiating features of Spitz nevi are patient age, sharp demarcation, symmetry, maturation of melanocytes at the base, and epithelial hyperplasia. None of these criteria are completely reliable, and multiple other criteria must be considered as well.

Spitz nevus versus spitzoid malignant melanoma: an evaluation of the current distinguishing histopathologic criteria

Because of the well-known difficulty in distinguishing between Spitz nevi and spitzoid malignant melanomas at the microscopic level, the critical importance of this task notwithstanding, expert dermatopathologists across the world have strenuously endeavored to identify histopathologic criteria that would assist microscopists in this effort. Many reports itemizing such criteria are extant. The objective of the current study was to determine which of these criteria serve as the most consistent discriminators. Using a population of 11 spitzoid melanomas and 12 Spitz nevi, we evaluated six sets of criteria purported to be helpful in differentiating between these entities. Overall, we found that six features had significant distinguishing capacity, namely, (1) Kamino bodies, (2) a brisk mitotic rate, (3) mitoses close to the base of the lesion, (4) abnormal mitoses, (5) symmetry, and (6) uniformity of nests from side to side. It is noteworthy that the first three of these rank among the six criteria itemized repeatedly in 50% or more of the sets of criteria evaluated.