The Spitz tumor 50 years later: revisiting a landmark contribution and unresolved controversy

The Spectrum of Spitz Melanocytic Lesions: From Morphologic Diagnosis to Molecular Classification

Spitz tumors represent a distinct subtype of melanocytic lesions with characteristic histopathologic features, some of which are overlapping with melanoma. More common in the pediatric and younger population, they can be clinically suspected by recognizing specific patterns on dermatoscopic examination, and several subtypes have been described. We now classify these lesions into benign Spitz nevi, intermediate lesions identified as “atypical Spitz tumors” (or Spitz melanocytoma) and malignant Spitz melanoma. More recently a large body of work has uncovered the molecular underpinning of Spitz tumors, including mutations in the HRAS gene and several gene fusions involving several protein kinases. Here we present an overarching view of our current knowledge and understanding of Spitz tumors, detailing clinical, histopathological and molecular features characteristic of these lesions.

A Practical Approach to the Diagnosis of Melanocytic Lesions

CONTEXT.—

Melanocytic lesions are common in routine surgical pathology. Although the majority of these lesions can be confidently diagnosed using well-established morphologic criteria, there is a significant subset of lesions that can be diagnostically difficult. These can be a source of anxiety for patients, clinicians, and pathologists, and the potential consequences of a missed diagnosis of melanoma are serious.

OBJECTIVE.—

To provide a practical approach to the diagnosis of melanocytic lesions, including classic problem areas as well as suggestions for common challenges and appropriate incorporation of ancillary molecular techniques.

DATA SOURCES.—

Literature search using PubMed and Google Scholar, incorporating numerous search terms relevant to the particular section, combined with contemporaneous texts and lessons from personal experience.

CONCLUSIONS.—

Although a subset of melanocytic lesions can be diagnostically challenging, the combination of a methodical approach to histologic assessment, knowledge of potential diagnostic pitfalls, opinions from trusted colleagues, and judicious use of ancillary techniques can help the pathologist navigate this difficult area.

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.

The landscape of fusion transcripts in spitzoid melanoma and biologically indeterminate spitzoid tumors by RNA sequencing

Kinase activation by chromosomal translocations is a common mechanism that drives tumorigenesis in spitzoid neoplasms. To explore the landscape of fusion transcripts in these tumors, we performed whole-transcriptome sequencing using formalin-fixed, paraffin-embedded (FFPE) tissues in malignant or biologically indeterminate spitzoid tumors from 7 patients (age 2-14 years). RNA sequence libraries enriched for coding regions were prepared and the sequencing was analyzed by a novel assembly-based algorithm designed for detecting complex fusions. In addition, tumor samples were screened for hotspot TERT promoter mutations, and telomerase expression was assessed by TERT mRNA in situ hybridization (ISH). Two patients had widespread metastasis and subsequently died of disease, and 5 patients had a benign clinical course on limited follow-up (mean: 30 months). RNA sequencing and TERT mRNA ISH were successful in six tumors and unsuccessful in one disseminating tumor because of low RNA quality. RNA sequencing identified a kinase fusion in five of the six sequenced tumors: TPM3-NTRK1 (2 tumors), complex rearrangements involving TPM3, ALK, and IL6R (1 tumor), BAIAP2L1-BRAF (1 tumor), and EML4-BRAF (1 disseminating tumor). All predicted chimeric transcripts were expressed at high levels and contained the intact kinase domain. In addition, two tumors each contained a second fusion gene, ARID1B-SNX9 or PTPRZ1-NFAM1. The detected chimeric genes were validated by home-brew break-apart or fusion fluorescence in situ hybridization (FISH). The two disseminating tumors each harbored the TERT promoter -124C>T (Chr 5:1,295,228 hg19 coordinate) mutation, whereas the remaining five tumors retained the wild-type gene. The presence of the -124C>T mutation correlated with telomerase expression by TERT mRNA ISH. In summary, we demonstrated complex fusion transcripts and novel partner genes for BRAF by RNA sequencing of FFPE samples. The diversity of gene fusions demonstrated by RNA sequencing defines the molecular heterogeneity of spitzoid neoplasms.

TERT Promoter Mutations Are Predictive of Aggressive Clinical Behavior in Patients with Spitzoid Melanocytic Neoplasms

Spitzoid neoplasms constitute a morphologically distinct category of melanocytic tumors, encompassing Spitz nevus (benign), atypical Spitz tumor (intermediate malignant potential), and spitzoid melanoma (fully malignant). Currently, no reliable histopathological criteria or molecular marker is known to distinguish borderline from overtly malignant neoplasms. Because TERT promoter (TERT-p) mutations are common in inherently aggressive cutaneous conventional melanoma, we sought to evaluate their prognostic significance in spitzoid neoplasms. We analyzed tumors labeled as atypical Spitz tumor or spitzoid melanoma from 56 patients with available follow-up data for the association of TERT-p mutations, biallelic CDKN2A deletion, biallelic PTEN deletion, kinase fusions, BRAF/NRAS mutations, nodal status, and histopathological parameters with risk of hematogenous metastasis. Four patients died of disseminated disease and 52 patients were alive and disease free without extranodal metastasis (median follow-up, 32.5 months). We found TERT-p mutations in samples from the 4 patients who developed hematogenous metastasis but in none of tumors from patients who had favorable outcomes. Presence of TERT-p mutations was the most significant predictor of haematogenous dissemination (P < 0.0001) among variables analyzed. We conclude that TERT-p mutations identify a clinically high-risk subset of patients with spitzoid tumors. Application of TERT-p mutational assays for risk stratification in the clinic requires large-scale validation.

Clinical and pathologic findings of Spitz nevi and atypical Spitz tumors with ALK fusions

Spitz tumors represent a group of melanocytic neoplasms that typically affect young individuals. Microscopically, the lesions are composed of cytologically distinct spindle and epithelioid melanocytes, with a range in the architectural display or the cells, their nuclear features, and secondary epidermal or stromal changes. Recently, kinase fusions have been documented in a subset of Spitz tumors, but there is limited information on the clinical and pathologic features associated with those lesions. Here, we report a series of 17 patients (9 male, 8 female) with spitzoid neoplasms showing ALK fusions (5 Spitz nevi and 12 atypical Spitz tumors). The patients' ages ranged from 2 years to 35 years (mean=17 y; median=16 y). Most lesions were located on the lower extremities and presented clinically as polypoid nodules. All tumors were compound melanocytic proliferations with a predominant intradermal growth. Tumor thickness ranged from 1.1 to 6 mm (mean=2.9 mm; median=2.5 mm). The most characteristic histopathologic feature of the tumors (seen in all but 2 lesions) was a plexiform dermal growth of intersecting fascicles of fusiform melanocytes. All but 2 tumors were amelanotic. All tumors were strongly immunoreactive for ALK. The ALK rearrangements were confirmed in all cases by fluorescence in situ hybridization (FISH), and the fusion partner was determined by quantitative polymerase chain reaction as TPM3 (tropomyosin 3) in 11 cases and DCTN1 (dynactin 1) in 6 cases. None of the 8 tumors that were analyzed by FISH for copy number changes of 6p, 6q, 9p, or 11q met criteria for melanoma. Two patients underwent a sentinel lymph node biopsy, and in both cases melanocyte nests were found in the subcapsular sinus of the node. Array comparative genomic hybridization of these 2 tumors revealed no chromosomal gains or losses. In conclusion, our study revealed that Spitz nevi/tumors with ALK rearrangement show a characteristic plexiform morphology and that ALK immunohistochemistry and FISH enable the accurate identification of this morphologic and genetic distinct subset of spitzoid neoplasms.

Imaging mass spectrometry--a new and promising method to differentiate Spitz nevi from Spitzoid malignant melanomas

BACKGROUND

Differentiating Spitz nevus (SN) from Spitzoid malignant melanoma (SMM) is one the most difficult problems in dermatopathology.

SPECIFIC AIM

To identify differences on proteomic level between SN and SMM.

METHODS

We performed Imaging Mass Spectrometry analysis on formalin-fixed, paraffin-embedded tissue samples to identify differences on proteomic level between SN and SMM. The diagnosis of SN and SMM was based on histopathologic criteria, clinical features, and follow-up data, which confirmed that none of the lesions diagnosed as SN recurred or metastasized. The melanocytic component (tumor) and tumor microenvironment (dermis) from 114 cases of SN and SMM from the Yale Spitzoid Neoplasm Repository were analyzed. After obtaining mass spectra from each sample, classification models were built using a training set of biopsies from 26 SN and 25 SMM separately for tumor and for dermis. The classification algorithms developed on the training data set were validated on another set of 30 samples from SN and 33 from SMM.

RESULTS

We found proteomic differences between the melanocytic components of SN and SMM and identified 5 peptides that were differentially expressed in the 2 groups. From these data, 29 of 30 SN and 26 of 29 SMM were recognized correctly based on tumor analysis in the validation set. This method correctly classified SN with 97% sensitivity and 90% specificity in the validation cohort.

CONCLUSIONS

Imaging Mass Spectrometry analysis can reliably differentiate SN from SMM in formalin-fixed, paraffin-embedded tissue based on proteomic differences.

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.

Spitz nevus in a Hispanic population: a clinicopathological study of 130 cases

Spitz nevus is an uncommon melanocytic nevus distinctive by its epithelioid and spindled melanocytes. Many studies have attempted to characterize Spitz nevus, but none of them in a Hispanic population. Our aim is to characterize the clinical and histopathological presentation of the Spitz nevus in a Hispanic population. A retrospective study was carried out from our files that included those cases histopathologically diagnosed as Spitz nevus. A blinded examination was performed to evaluate the histopathological characteristics of 130 lesions. The demographics of the patients, the anatomic location, and the accuracy of the clinical diagnosis were analyzed. Eighty-one females and 49 males (ratio of 1.7:1) were included in the study. The mean age was 18.8 years. Overall, the most common location was the lower extremities (41%), followed by the upper extremities (27%), trunk (16%), and head and neck (16%). The nevi followed a similar anatomic distribution in females and males. The lesions were clinically diagnosed with accuracy in 20% of the cases and characterized as a pigmented papule in 42% of the cases. Upon histopathological evaluation, most nevi exhibited symmetry (84%), were well circumscribed (91%), and exhibited epidermal hyperplasia (69%). The junctional type was seen in 42% of the cases, the compound type in 38%, and the dermal type in 20%. Sixty-eight percent of nevi were mostly composed of epithelioid melanocytes, the spindled-shaped melanocytes predominated in 17% of cases, and 12% were composed of both epithelioid and spindled-shaped melanocytes. Multinucleated melanocytes were seen in 7% of nevi, mostly in the epithelioid Spitz nevus (67%). Abundant melanin was observed in 51 cases, from which the most common variant was the classic Spitz nevi. The typical dull eosinophilic globules (Kamino bodies) were observed in a minority of the cases (11%), mostly in the classic Spitz nevus. The most common variant was the classic Spitz nevus (65%), followed by the dermal Spitz nevus (15%). In conclusion, Spitz nevus in a Hispanic population most commonly presents as a pigmented papule on the lower extremities irrespective of sex and age. It is characterized by a melanocytic proliferation most commonly composed of nested epithelioid melanocytes in a junctional or compound arrangement, with the presence of abundant melanin.

Atypical spitzoid melanocytic tumors with positive sentinel lymph nodes in children and teenagers, and comparison with histologically unambiguous and lethal melanomas

Children and teenagers with a positive sentinel lymph node (SLN) after a prior diagnosis of an atypical spitzoid melanocytic tumor (ASMT) are usually cared for clinically in the same way as patients with melanoma. Little is known about long-term follow-up of these individuals to determine whether this practice is appropriate. To learn more about the biology of these tumors we retrospectively reviewed the clinical and pathologic findings of children and teenagers (<18 y of age at the time of diagnosis) with an ASMT, positive SLN and follow-up of at least 3 years. Their findings were compared with histologically unambiguous melanomas of children or teenagers, who had a positive SLN or died of metastatic melanoma. Eleven individuals, 6 girls and 5 boys, with primary ASMT and positive SLN were identified. The primary tumors ranged in thickness from 2.1 to 12 mm (median, 4.6 mm; mean, 5 mm). The tumor mitotic rate ranged from 1 to 10 mitoses/mm (median, 3/mm, median, 3/mm). The positive SLNs included 6 nodes with intranodal melanocytic aggregates measuring <1 mm in greatest dimension, and 5 nodes, in which the size of the melanocyte deposits was >/=1 mm. All the patients with ASMT and positive SLN remained free of disease with a median follow-up of 47 months (mean, 61 mo, range: 36 to 132 mo). In contrast, 2 of 5 patients <18 years of age with a histologically unambiguous melanoma and a positive SLN died of metastatic melanoma. The overall disease-specific mortality rate for all patients <18 years of age diagnosed with melanoma was 12%. Our findings confirm that children and teenagers with ASMTs and positive SLNs have a less aggressive clinical course than those with histologically unambiguous melanoma.

Sentinel lymph node biopsy in pediatric and adolescent cutaneous melanoma patients

BACKGROUND

The rarity of melanoma in young patients, particularly pediatric ones, has to date precluded any valid comparisons being made between young patients and adults undergoing sentinel lymph node biopsy (SLNB) for intermediate thickness localized melanoma. The present study takes advantage of the large Sydney Melanoma Unit (SMU) database to clarify this issue.

MATERIALS AND METHODS

Clinical and pathologic data on pediatric and adolescent AJCC Stage I and II cutaneous melanoma patients aged <20 years undergoing SLNB at the SMU between January 1993 and February 2008 were reviewed. SLNB positivity rates and outcomes in these patients were compared with adult SMU patients.

RESULTS

In 55 young patients, overall median tumor thickness was 1.7 mm (range, 0.6-5.2 mm) and overall SLNB positivity rate was 14 of 55 (25%), tumors tending to be thicker (median, 2.6 mm), and SLNB positivity rate higher (2 of 6; 33%) in patients aged <10 years. Of the 14 patients, 13 underwent immediate completion lymph node dissection (CLND); 2 patients had non-SLN metastases (15.4%). Only 0.7% of a total of 295 lymph nodes removed at CLND were involved with melanoma. In 14 SLNB-positive patients with follow-up data, 3 (21%) have died from melanoma after a median follow-up of 60 months, compared with 42% of 356 SLNB positive adults.

CONCLUSIONS

Although the SLNB positivity rate was higher in pediatric and adolescent melanoma patients than in adults (25% vs. 17%, respectively), non-SLN positivity and melanoma-specific death rates were low.

Sentinel lymph node biopsy for patients with diagnostically controversial Spitzoid melanocytic tumors?

The distinction of a Spitz nevus from melanoma can be very difficult. Pathologists may disagree on whether a Spitzoid melanocytic proliferation is benign or malignant, or acknowledge uncertainty about the diagnosis. As long as melanoma is suspected or strongly considered, a clinical management plan is often adopted as if the patient had melanoma, which may include sentinel lymph node (SLN) biopsy for staging. The findings of the sentinel node may resolve the diagnostic controversy about the primary tumor, but there is also the risk for more diagnostic confusion, uncertainty, and errors. We review the arguments in favor and against SLN biopsy for patients with diagnostically controversial Spitzoid melanocytic tumors, summarize current experience, and illustrate diagnostic pitfalls. Although SLN biopsy provides prognostic information helpful for clinical trials, we caution against performing the procedure as a diagnostic adjunct.

Multiple skin metastases of malignant melanoma with unusual clinical and histopathologic features in an immunosuppressed patient

Immunosuppressive regimens may have significant impact on the number of pigmented lesions and the clinical appearance of nevi. Whether immunosuppression can also influence the clinical and histopathologic appearance of malignant melanocytic lesions is still a matter of debate. A patient was immunosuppressed because of heart and bone marrow transplantation. A clinically inconspicuous mole was removed from the left flank and was considered to be a papillomatous nevus. After 1 year, the patient developed multiple pigmented lesions over the entire body, which presented clinically as benign papillomatous nevi and histologically as atypical Spitz nevi. Three months later melanoma metastases were removed from the patient's left axilla, which finally resulted in the death of the patient. Thus, in retrospect, the eruptive pigmented lesions have to be considered as cutaneous melanoma metastases. The atypical clinical and histopathologic appearance of the melanocytic lesions as well as the course of disease may have been influenced by the immunosuppression.

Sentinel lymph node biopsy in histologically ambiguous melanocytic tumors with spitzoid features (so-called atypical spitzoid tumors)

BACKGROUND

The distinction of Spitz nevi from melanomas with spitzoid morphology can be difficult. For lesions with overlapping histopathologic features, it may be impossible to predict their malignant potential with certainty. The current study evaluated the role of sentinel lymph node (SLN) biopsy in patients with such atypical spitzoid tumors.

METHODS

The clinical and histopathologic features of 21 patients with atypical spitzoid tumors who underwent SLN biopsy were reviewed and correlated with the presence or absence of metastatic tumor in their corresponding SLNs.

RESULTS

The atypical histopathologic features that were most frequently present included incomplete maturation (11 patients, 52%), two or more dermal mitoses per square millimeter (13 patients, 62%), and deep dermal mitoses (11 patients, 52%). Six patients (29%) showed SLN metastasis. There were histopathologic differences between tumors with positive SLN when compared with tumors with negative SLN: mean tumor thickness (3.38 mm vs. 2.04 mm), incomplete maturation (83% vs. 40%), median dermal mitotic rate (3.5/mm(2) vs. 2/mm(2)), deep dermal mitoses (83% vs. 47%), and expansile dermal nodules (50% vs. 13%). However, of these, only the difference in mean tumor thickness reached statistical significance (P < .05).

CONCLUSIONS

SLN biopsy offers a means of assessing the metastatic potential of atypical spitzoid tumors and aids in the management of these patients by selecting patients who may benefit from a regional node field dissection and those in whom the use of adjuvant therapies could be considered.

Sentinel Lymph Node Biopsy for Atypical Melanocytic Lesions with Spitzoid Features

INTRODUCTION

Sentinel lymph node biopsy (SLNB) is routinely used as a staging procedure for melanomas, however may also assist in understanding the biology of atypical and controversial spitzoid melanocytic skin lesions.

METHODS

Five hundred and forty-nine sentinal lymph node excisions were performed over a 5-year period. Fourteen patients with controversial melanocytic lesions were identified and of these ten underwent SLNB. The histology of the primary skin lesion and corresponding sentinal lymph nodes were evaluated and correlated with outcome.

RESULTS

Thickness of the primary melanocytic lesion ranged from 1.22 to 4 mm. Fifty percent of patients were less than 17 years of age. Ten patients underwent SLNB and three cases (30%) displayed metastatic disease in the SLNB specimen. All three patients were under 17 years of age and all underwent completion axillary dissection. One completion axillary dissection had an additional node with metastasis on routine H&E and immunohistochemical staining. No capsular invasion was seen. All three cases with metastatic disease received adjuvant systemic therapy and remain disease free at 29, 49 and 57 months follow-up. All patients with a negative SLNB remain disease free at mean follow-up of 28.1 months (range: 13-40 months).

CONCLUSION

Our results confirm that some of these spitzoid lesions metastasize to regional lymph nodes and SLNB is a valuable adjunct tool in staging these lesions. However, molecular studies and a prolonged follow-up are needed to determine whether these lesions, especially those occurring in children are comparable to stage matched overt melanoma in adults.

Analysis of Mutations in B-RAF, N-RAS, and H-RAS Genes in the Differential Diagnosis of Spitz Nevus and Spitzoid Melanoma

A definite diagnosis cannot be established based on histologic features alone in a large number of Spitz nevi and spitzoid melanomas. In a vast majority of common benign and malignant melanocytic lesions, B-RAF and N-RAS mutations were described, but these were not detected in Spitz nevi. In contrast, H-RAS mutations were frequently encountered in Spitz nevi, but only rarely in melanomas. To date, B-RAF mutation analysis has not been reported in atypical Spitz nevi, and there are only a few reports of it in spitzoid melanomas. We analyzed 96 formalin-fixed, paraffin-embedded spitzoid melanocytic lesions for hotspot mutations in B-RAF, N-RAS, and H-RAS genes to test the assumption whether mutation analysis would assist a more accurate diagnosis of spitzoid melanocytic lesions, which are notoriously difficult to classify. B-RAF or N-RAS mutations were observed in 31 of 36 (86%) spitzoid melanomas, and in 6 of 7 (86%) spitzoid melanoma metastases. In contrast, none of the 14 Spitz nevi and none of the 16 atypical Spitz nevi had mutations in any of the three genes. A B-RAF or N-RAS mutation was found in 8 of 23 (35%) spitzoid lesions suspected for melanoma. H-RAS mutations were detected in 4 of 14 (29%) Spitz nevi, in 3 of 22 (14%) atypical Spitz nevi, in 1 of 15 (7%) spitzoid tumors suspected for melanoma, but in none of the spitzoid melanomas. These results strongly indicate that Spitz nevi and spitzoid melanomas are genetically unrelated entities. Furthermore, we can conclude that mutation analysis may be useful as an additional diagnostic tool to distinguish between benign and malignant spitzoid lesions.

Combined naevus: a benign lesion frequently misdiagnosed both clinically and pathologically as melanoma

BACKGROUND

Combined naevi are characterised pathologically by the presence of two or more different types of melanocytic naevi in a single lesion. They are prone to clinical and pathological misdiagnosis as melanoma. Misdiagnosis may result in inappropriate treatment, patient anxiety and medicolegal consequences.

AIMS

With the aim of reducing the incidence of misdiagnosis, this study documents the clinical and pathological features of a large series of combined naevi and describes how to distinguish them from melanoma.

PATIENTS AND METHODS

The slides of skin lesions from 220 patients that were coded as combined naevus between 1990 and 2001 were retrieved from the archival files of the Department of Anatomical Pathology, Royal Prince Alfred Hospital, Sydney, Australia. The clinical notes, letters from referring pathologists (for consultation cases) and slides were reviewed and for each lesion clinical and pathological features were assessed. Thirty-eight cases were excluded either because they included only one naevus component or because there were atypical pathological features in the slides available for review. The remaining 182 cases formed the study population.

RESULTS

The patients included 92 females and 87 males (1.1:1). In three cases the gender was not known. Mean and median patient ages were 29.6 and 28 years, respectively. The anatomical site of involvement was the trunk in 64 cases (35.2%), head and neck region in 43 cases (23.6%), upper extremity in 40 cases (22.0%), lower extremity in 18 cases (9.9%) and perineum and buttock region in eight cases (4.4%). In nine cases the site of involvement was not known. A pre-operative clinical diagnosis was recorded in 126 cases; of these, melanoma was suspected clinically in 33 cases (26.2%) while combined naevus was diagnosed clinically in only three cases (2.4%). Histologically, 180 cases included two different naevus components, and in two cases three different naevus components were present. The most common combination was a common acquired naevus of compound type associated with a blue naevus of deep penetrating naevus type; this occurred in 57 cases (31.3%). The referring pathologist recorded a preferred diagnosis in 88 of 122 consultation cases; of these, melanoma was suspected in 23 cases (26.1%) and in 23 cases combined naevus was favoured (26.1%).

CONCLUSIONS

Combined naevus is an uncommon type of melanocytic naevus that is frequently misdiagnosed both clinically and pathologically. Knowledge and recognition of the pathological features of combined naevi and the important features that distinguish them from melanomas should reduce the frequency of misdiagnosis.

“Atypical” Spitz’s Nevus, “Malignant” Spitz’s Nevus, and “Metastasizing” Spitz’s Nevus: A Critique in Historical Perspective of Three Concepts Flawed Fatally

Our purpose in undertaking this Arbeit was to review all articles published about "atypical" Spitz's nevus, "malignant" Spitz's nevus, and "metastasizing" Spitz's nevus, to criticize them in a fashion that illuminates, and to come to conclusions compellingly about those subjects. We found that an overwhelming majority of neoplasms that claimed to be "atypical Spitz's nevus," "metastasizing Spitz's nevus," and "malignant Spitz's nevus" were, in fact, melanomas ( Table 1). Moreover, in our estimation, those designations, and variants of them, like "atypical Spitz's lesion," "atypical dermal melanocytic lesion with features of Spitz's nevus," "atypical Spitzoid melanocytic neoplasm," and "problematic Spitzoid melanocytic lesion," are mere evasions from a diagnosis, straightforwardly, of either Spitz's nevus or melanoma. Diagnoses in pathology equally bogus are "minimal deviation melanoma," "borderline melanoma," "nevoid melanoma," "potentially low-grade melanocytic neoplasm," and "melanocytic lesion of uncertain biologic potential." Rather than admit uncertainty forthrightly, those who employ circumlocutions like those just mentioned resort to linguistic maneuvers that, at first blush, seem to be "academic" and constructed in such a way as to appear to convey confidence, rather than tentativeness, on the part of a histopathologist. On further scrutiny, however, each of those cliches is revealed to be devoid of content. For example, "malignant" Spitz's nevus and "metastasizing" Spitz's nevus not only are contradictions in terms, but they are outrageous violations of fundamental principles of classic Virchowian pathology, and "atypical" Spitz's nevus not only is a redundancy because the neoplasm was so atypical to Spitz, herself, she insisted (from the time she spawned the idea in 194 through 1951 it was a "malignant melanoma," but is abject intellectually, those who invoke it never setting forth, in clear-cut fashion, criteria for what constitutes a "typical" Spitz's nevus in contradistinction to an "atypical" one.

Pigmented epithelioid melanocytoma: a low-grade melanocytic tumor with metastatic potential indistinguishable from animal-type melanoma and epithelioid blue nevus

In the course of a study of borderline melanocytic tumors, we observed a distinctive group of lesions characterized by features very similar to those previously described in the literature as "animal-type melanoma" and epithelioid blue nevus of Carney complex. We have designated these lesions as pigmented epithelioid melanocytoma (PEM). Herein, we present a clinical-pathologic analysis of 41 consecutive PEM from 40 patients and compare them with 11 epithelioid blue nevi from patients with Carney complex. PEM occurred in both sexes of different ethnic backgrounds, including white, Hispanic, black, Asian, and Persian. The median age of occurrence was 27 years (range 0.6-78 years). Tumors had wide distribution with extremities being the most common site. The tumors were formed by deep dermal (mean Breslow's thickness 3.3 mm) proliferation of heavily pigmented epithelioid and/or spindled melanocytes. Five lesions were part of combined nevus. Ulceration was present in 7 cases. Tumor necrosis was present in 1 case. Regional lymph nodes were sampled in 24 cases (59%). In 11 cases, lymph nodes contained metastases (46%). Liver metastases occurred in 1 case. None of the patients died of disease. Clinical follow-up of more than a year (mean 32 months, range up to 67 months) was available in 27 cases (67%). We found no histologic criteria separating metastasizing and nonmetastasizing PEM. Ulceration was the only feature more common in PEM than epithelioid blue nevi of Carney complex. Otherwise, they were histologically indistinguishable. Our data show that PEM is a unique low-grade variant of melanoma with frequent lymph node metastases but indolent clinical course. We suggest that PEM be considered as a provisional histologic entity encompassing both animal-type melanoma and epithelioid blue nevus.

Melanomas in prepubescent children: review comprehensively, critique historically, criteria diagnostically, and course biologically

Our series was comprised of 11 children age 10 years or younger (6 were younger than age 5) with primary cutaneous melanoma. All of the melanomas occurred de novo and all metastasized; one child died. In no instance was melanoma a clinical consideration, and in none did the histopathologist who first "signed out" the case make a diagnosis of melanoma. Despite the inability of clinicians and pathologists to diagnose correctly, with repeatability, melanomas that develop in children yet to be pubescent, those neoplasms, nonetheless, are melanomas and, therefore, criteria employed currently for diagnosis of melanoma, especially clinically, must be refined in order that they be applicable equally to melanomas in pre- and postpubescents. The vaunted ABCDs (Asymmetry, Border irregular, Color variability, Diameter >6.0mm) surely do not work for melanomas that appear in children who are prepubescent. Additionally, melanomas that occur in these children have distinctly different architectural and cytopathological features from those that arise in postpubescents, often being confused as they are by conventional microscopy with a Spitz's nevus. As a rule, melanomas in prepubescent children grow much more rapidly then those in adults but, like them, have the capability to disseminate widely and cause death.

A current dilemma in histopathology: atypical spitz tumor or Spitzoid melanoma?

Both clinically and histopathologically, melanoma of childhood is a rarely encountered lesion. In addition, it has particular histopathologic diagnostic problems. Differential diagnosis of this lesion and Spitz nevus is at times very problematic, in that distant metastases and death of the patient may be the only diagnostic criteria for some cases. We present a 4-year-old girl with an atypical melanocytic neoplasm with Spitzoid features on the left subscapular region.

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.

Sentinel lymph node biopsy in patients with diagnostically controversial spitzoid melanocytic tumors

Melanomas can be difficult to diagnose histologically if they deviate in their growth pattern or cytology only minimally from a nevus. On occasion, even experts on melanocytic lesions may not reach a consensus on whether a lesion is a benign but unusual nevus or a malignant melanoma mimicking a nevus. This diagnostic dilemma is particularly well known for the distinction of Spitz nevus from melanoma. Diagnostic uncertainty and disagreement among consultant pathologists lead to confusion about the prognosis and clinical management of patients. In this study we present the clinical and pathologic findings of 10 patients with diagnostically controversial melanocytic tumors, who underwent sentinel lymph node biopsy. In all of these cases, the diagnostic controversy among experts was between Spitz nevus and melanoma. Seven patients were female, and three were male, ranging in age from 7 to 46 years (mean 21 years). Histologic examination of the sentinel lymph nodes revealed tumor deposits in the lymph node parenchyma in 5 of 10 patients. Among patients with positive sentinel lymph nodes, two had satellite nodules and one showed additional tumor deposits in three nonsentinel regional lymph nodes. All patients are alive and free of disease with a follow-up of 10-54 months (mean 34 months). Our study illustrates the role of a sentinel lymph node biopsy in the evaluation of patients with diagnostically controversial melanocytic tumors. Although the presence of metastatic tumor deposits in the sentinel lymph node supports the diagnosis of malignant melanoma, further studies are needed to determine the prognostic significance of the sentinel lymph node findings in such patients.