ORIGINAL

ARTICLES

Atypical Spitz tumors in patients younger than 18 years Daniela Massi, MD,a Carlo Tomasini, MD,c Rebecca Senetta, MD,d Milena Paglierani, BSc,a Francesca Salvianti, PhD,b Maria Elena Errico, MD,e Vittoria Donofrio, MD,e Paola Collini, MD,f Gabrina Tragni, MD,g Angela Rita Sementa, MD,i Franco Rongioletti, MD,j Renata Boldrini, MD,k Andrea Ferrari, MD,h Claudio Gambini, MD,i and Maria Cristina Montesco, MDl Florence, Turin, Naples, Milan, Genoa, Rome, and Padua, Italy Background: Diagnosis and proper management of atypical Spitz tumors in pediatric age are still controversial. Objective: We sought to investigate the clinicopathological and molecular features of atypical Spitz tumors in patients aged 18 years or younger. Methods: We performed a retrospective clinicopathological and fluorescence in situ hybridization study on 50 pediatric atypical Spitz tumors. Results: Parameters that were significantly correlated with a diagnosis of atypical Spitz tumors over Spitz nevus included asymmetry, level IV/V, lack of maturation, solid growth, nuclear pleomorphism, high nuclear-cytoplasmic ratio, atypical and deep mitoses, and more than 6 mitoses/mm2. In the atypical Spitz tumors group, a significantly higher mitotic rate was observed in prepuberal age (P = .04). The 4-probe fluorescence in situ hybridization melanoma assay did not discriminate atypical Spitz tumors from Spitz nevi. Heterozygous 9p21 loss was found in 3 of 37 cases and homozygous 9p21 loss in 2 of 37 cases. Only 1 child experienced a fatal outcome, showing genetic abnormalities by melanoma fluorescence in situ hybridization probe and a heterozygous 9p21 deletion. Limitations: The limited number of adverse outcomes did not allow the prognostic analysis of single morphologic features. Conclusion: Pediatric atypical Spitz tumors are associated with minimal lethal potential. Atypical Spitz tumors require complete excision and careful follow-up while our data do not support any clinical benefit for the sentinel lymph node biopsy procedure and completion lymphadenectomy. ( J Am Acad Dermatol 2015;72:37-46.) Key words: atypical Spitz tumor; fluorescence in situ hybridization; pediatric age; sentinel lymph node; Spitz nevus.

A

lthough significant improvement has been obtained in the histopathological definition of atypical Spitz tumors,1-3 it is fair to conclude that understanding the true biologic significance of atypical Spitz tumors is still a work in progress. The distinct morphologic features for

From the Departments of Surgery and Translational Medicine,a and Biomedical, Experimental, and Clinical Sciences,b University of Florence; Dermatopathology Section, Azienda Ospedaliera Citta della Salute e della Scienza, Turinc; Department of Medical Sciences, University of Turind; Pediatric Hospital SantobonoPausilipon, Naplese; Units of Soft Tissue and Bone Pathology, Histopathology, and Pediatric Pathology,f Dermatopathology,g and Pediatric Oncology,h Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Istituto Nazionale dei Tumori, Milan; Istituto Giannina Gaslini, Genoai; IRCSS AOU S. Martino, Department of Health Sciences, DISSAL, University of Genoaj; Bambino Ges u Children’s Hospital, Romek; and Veneto Institute of Oncology Istituto Oncologico Veneto Istituto di Ricovero e Cura a Carattere Scientifico (IOV IRCCS), Padua.l

Abbreviations used: AIEOP: FISH: SLN: SLNB:

Associazione Italiana Ematologia Oncologia Pediatrica fluorescence in situ hybridization sentinel lymph node sentinel lymph node biopsy

Supported by Fondazione Cassa di Risparmio di Pistoia e Pescia, Ministero dell’Istruzione, dell’Universita e della Ricerca Programmi di Ricerca di Rilevante Interesse Nazionale (MIUR PRIN) 2012JJX494_002. Conflicts of interest: None declared. Accepted for publication September 24, 2014. Reprint requests: Daniela Massi, MD, Division of Pathological Anatomy, Department of Surgery and Translational Medicine, University of Florence, Largo Brambilla 3, 50134 Florence, Italy. E-mail: [email protected]. Published online October 25, 2014. 0190-9622/$36.00 Ó 2014 by the American Academy of Dermatology, Inc. http://dx.doi.org/10.1016/j.jaad.2014.09.049

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atypical Spitz tumors have been known for whether such criteria correlate with molecular decades but how one subjectively clusters them genetic data and clinical outcome. In this results in high interobserver disagreement, which multicentric, collaborative, retrospective study, we may be reflected in diverse final diagnoses.3-6 Thus, it analyzed the pathological features, FISH data, and may be acknowledged that when dealing with clinical outcome of a series of atypical Spitz tumors Spitzoid proliferations morphology is not currently observed in patients aged 18 years or younger. our best diagnostic tool in predicting biological behavior, and recently there METHODS has been a significant Criteria for inclusion CAPSULE SUMMARY expansion of molecular The study included a data assays, namely fluorescence set of 83 primary cutaneous In pediatric patients with atypical Spitz in situ hybridization (FISH), melanomas and ambiguous tumor the clinical management is still a comparative genomic hymelanocytic proliferations in matter of debate. bridization, and mutational patients aged 18 years or The rigorous application of the cytologic analyses, that are now being younger, retrospectively retdiagnostic criteria is mandatory to avoid used to screen atypical rieved from the pathology misinterpretations. Our results confirm Spitz tumors for genomic abfiles of both Associazione Itthe minimal lethal potential in patients normalities.7-15 It has been aliana Ematologia Oncologia with atypical Spitz tumor aged 18 years Pediatrica (AIEOP) and nondemonstrated that 9p21 may or younger. AIEOP centers. The study was be helpful in lesions with supported by Tumori Rari Spitzoid morphology, and In pediatric patients with atypical Spitz in Eta Pediatrica, a nationalcan increase the sensitivity tumor a complete excision and a careful scale project on rare pediatric of the current melanoma follow-up are the best management. tumors under the auspices of FISH probe assay in identithe AIEOP, in cooperation fying Spitzoid melanomas with the Societa Italiana Chirurgia Pediatrica.27 without impairing specificity.8,9 It has been also shown that atypical Spitz tumors appear to be Ambiguous melanocytic proliferations included composed of genetically and biologically distinct cases originally diagnosed as melanocytic tumors of entities: HRAS mutant, BRAFV600E/BAP1 mutant, and uncertain malignant potential, atypical Spitz nevus/ tumor, and Spitzoid melanocytic tumor of uncertain a (likely still heterogeneous) category of tumors with malignant potential. For comparison, we evaluated a yet unknown genetic abnormalities.10,15 Recently, second data set of 16 lesions, unambiguously classikinase fusions including ROS1, NTRK1, ALK, BRAF, fied as Spitz nevi, in patients aged 18 years or and RET have been documented in a mutually younger. exclusive pattern in Spitzoid neoplasms (55% of Seven pediatric patients of the current series were Spitz nevi, 56% of atypical Spitz tumors, and 39% of originally reported in our previous study,12 which Spitzoid melanomas).16 Furthermore, it has been shown that Spitz nevi/tumors with ALK rearrangeincluded both pediatric and adult patients with ment show a characteristic plexiform morphology atypical Spitz tumor, analyzed with FISH but currently it is unknown whether the presence or conventional melanoma probe. absence of a kinase fusion of a particular type is Available histopathological slides were first associated with a more indolent or aggressive clinical independently reviewed and then re-evaluated on course.17 the multiheaded microscope by 3 pathologists with Atypical Spitz tumors may be observed in specific background in dermatopathology (D. M., M. pediatric age and in this case the lack of unanimously C. M., C. G.). Upon revision, 29 of 83 (34.9%) lesions established management recommendations, were excluded from the analysis. In all 23 cases were including usefulness of sentinel lymph node (SLN) regarded as cytologically not Spitzoid19 (specifically 18-26 biopsy (SLNB), represents a major concern. 11 pediatric melanomas and 12 non-Spitzoid There is relative paucity of studies in the literature ambiguous melanocytic proliferations including on large series of atypical Spitz tumor in pediatric age atypical blue and deep penetrating nevi) whereas 6 evaluated with both conventional FISH melanoma cases were excluded because no additional tissue and 9p21 FISH analysis in light of well-documented was available or because of lack of clinical follow-up. There is also a strong need to assess the information. diagnostic weight of the single commonly shared For the remaining 54 Spitzoid melanocytic lesions, cytohistopathological criteria for diagnosis of a consensus final diagnosis was reached by adopting atypical Spitz tumor in pediatric age and to identify the following categories: (1) Spitz nevus; and d

d

d

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Massi et al 39

(2) atypical Spitz tumors, including those with indeterminate or malignant biological potential. Criteria for a diagnosis of atypical Spitz tumor were those previously described by Barnhill.2,3 The study was approved by the institutional review board and performed according to the standards of the institutional ethical committee and the Helsinki Declaration of 1975 as revised in 1983.

(14.8%) cases in which there was discordance among the 3 dermatopathologists, slides were reviewed and discussed at the multiheaded microscope until a final consensus was reached. Four out of 54 (7.4%) were finally diagnosed as Spitz nevus and 50 of 54 (92.6%) as atypical Spitz tumors. The 16 Spitz nevus of the second independent data set were also reviewed and the original diagnosis was confirmed.

Data collection Clinical data were obtained by medical records. Follow-up data were available for 53 of 54 (98.1%) cases. For statistical analysis, the following histopathological parameters were assessed: Clark level; thickness (# 1 mm vs [ 1-2 mm); asymmetry; circumscription; ulceration; peripheral pagetoidism; deep border (pushing vs infiltrating); lack of architectural maturation; lack of cytologic maturation; solid growth; necrosis; cytotype (epithelioid vs spindle vs mixed); nuclear pleomorphism; high nuclear-cytoplasmic ratio; mitotic rate (\2/mm2 vs 2-6/mm2 vs [6/mm2); deep mitoses; atypical mitoses; presence of plasma cells; architecture (junctional vs compound vs dermal); apoptosis; desmoplasia; inflammatory infiltrate; epidermal consumption; and presence of prominent nucleoli.

Clinical features The atypical Spitz tumors group included 50 cases and patient age ranged from 1 to 18 years (mean 8.3 years, median 8.5 years). In all, 31/50 patients (62%) were male and 19/50 (38%) were female. Lesions were located on the lower limb (26/50, 52%), upper limb (16/50, 32%), trunk (5/50, 10%), and head/neck (2/50, 4%). In 1 case site was unknown. Lesions ranged in size from 2.3 to 30 mm (mean 7.2 mm, median 7 mm). Type of excision was incisional biopsy/shave (n = 4), shave followed by re-excision (n = 5), excision with clear margins (n = 32), and excision with clear margins followed by re-excision (n = 9). Overall, SLNB was performed in 15 of 50 (30%) patients and a SLN micrometastasis was detected in 2 cases. After SLNB, both cases underwent to a completion lymph node dissection that revealed negative findings. In addition, 1 patient given the diagnosis of atypical Spitz tumors, who did not received SLNB procedure, underwent an inguinal lymph node dissection showing in 2 enlarged lymph nodes small intracapsular and subcapsular deposits of melanocytes with atypical cytologic appearance similar to the primary lesion. In this last case no further evidence of disease was observed after 45 months of follow-up. The duration of follow-up ranged from 1 to 300 months (mean 49.4 months, median 37 months). In all, 48 patients were alive, no evidence of disease, at the time of analysis. One 4-year-old girl (1/50, 2%) had progression of disease at 72 months after primary diagnosis and died of disease at 96 months. The primary lesion had been incompletely excised and SLNB was not performed. A 14-year-old boy showed disease progression with in transit metastasis 20 months after the primary diagnosis, and is alive after 25 years of follow-up. One patient was lost to follow-up. Representative examples of atypical Spitz tumors are shown in Figs 1-4. We grouped in the second cohort the lesions classified as Spitz nevus upon revision (n = 4) and the 16 lesions classified as unequivocal Spitz nevus (n = 20). The patients’ age ranged from 2 to 18 years (mean 8.75 years, median 7.5 years). Ten of 20 (50%) patients were male and 10 of 20 (50%) were female. Site of the primary lesion was lower limb (11/20,

FISH analysis FISH analysis and interpretation for conventional melanoma probe (RREB1, MYB, CCND1, CEP6) was performed as previously described.12,28 FISH using the Vysis LSI CDKN2A SpectrumOrange/CEP 9 SpectrumGreen probes kit (Abbott Molecular Inc, Des Plaines, IL) was performed as previously described applying the criteria for FISH positivity as previously suggested8: greater than 29% of enumerated cells with homozygous deletion of 9p21. Statistical analysis Data were analyzed with software (SPSS, Version 17, IBM Corp, Armonk, NY). Differences in the distribution of variables were tested using either the Fisher exact test or Pearson x 2 for categorical variables, whereas a parametric Student t test was used to compare the distribution of the size (continuous variables). All tests were 2-sided. A multivariate logistic regression analysis was performed. A P value less than .05 was considered statistically significant.

RESULTS After revision of the first data set, we identified 54 cases that fulfilled the criteria for melanocytic lesions with Spitzoid features. Upon revision, in 8 of 54

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Fig 1. Atypical Spitz tumor in the lower limb of 8-year-old boy. The lesion measures 6 mm in thickness. The child is alive, no further evidence of disease after 127 months follow-up. (A and B, Hematoxylin and eosin stain; original magnifications: A, 32.5; B, 340.)

Fig 2. Atypical Spitz tumor in the upper limb of a 3-year-old girl. The lesion is 7.5 mm in thickness. Sentinel lymph node was negative. Patient was alive with no evidence of disease at 16 months follow-up. (A and B, Hematoxylin and eosin stain; original magnifications: A, 32.5; B, 340.)

55%) head/neck (4/20, 20%), upper limb (4/20, 20%), and trunk (1/20, 5%). Lesions ranged in size from 3 to 8 mm (mean 5.56 mm, median 5 mm). All patients were alive at the time of analysis, only 1 patient was lost (duration of follow-up 18-152 months; mean 46.42 months, median 40 months). One patient underwent SLNB that revealed negative findings. Table I summarizes demographics, clinical findings, and outcome for atypical Spitz tumor and Spitz nevus included in the study. Pathological features and correlation with final diagnostic categories The analysis of morphologic features was performed merging the 2 data sets (70 cases: 20 Spitz nevus and 50 atypical Spitz tumors). A significant statistical correlation emerged between final histologic diagnosis (Spitz nevus vs atypical Spitz tumor) and some morphologic parameters, as shown in Table II. By multivariate logistic regression,

cytologic maturation was the only independent predictor of an atypical Spitz tumor diagnosis [exp(B) = 0.02; 95% confidence interval 0.0010.662; P = .028]. Lack of cytologic maturation for a diagnosis of atypical Spitz tumor showed: specificity 68%; sensitivity 77%; positive predictive value 86%; and negative predictive value 54%. Among atypical Spitz tumors, we found a significant correlation between mitotic rate and thickness (P = .02) as 100% of cases with more than 6 mitoses/mm2 had more than 2 mm in thickness. Significant correlation was also observed between level and age, stratified into 2 categories: preadolescence and early adolescence (# 14 years) and adolescence ([14 years) (P = .04). All lesions infiltrating the subcutaneous fat (level V) were found in patients aged 14 years or younger. Age correlated with mitotic rate (P = .04); all atypical Spitz tumors with greater than 6 mitoses/mm2 were diagnosed in preadolescence and early adolescence age (5 of 5). Table III summarizes histopathological features by

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Fig 3. A and B, Atypical Spitz tumor in the lower limb of a 5-year-old girl. The lesion measures 3 mm in thickness. The patient did not receive a sentinel lymph node biopsy procedure but underwent an inguinal lymph node dissection showing in 2 enlarged lymph nodes small intracapsular and subcapsular deposits of atypical melanocytes. No further evidence of disease was observed after 45 months of follow-up. C, Melanocytic cells with homozygous deletion of 9p21 by fluorescence in situ hybridization with a CDKN2A (orange) and chromosome 9 (green) -specific probe. (A to C, Hematoxylin and eosin stain; original magnifications: A, 310; B, 340; C, 363.)

Fig 4. A and B, Atypical Spitz tumor in the upper limb of a 4-year-old girl. The lesion is 4.2 mm in thickness. The child developed local recurrence (at 72 months), developed nodal and visceral metastases, and died of disease at 96 months from original diagnosis. C, Fluorescence in situ hybridization with LSI CDKN2A SpectrumOrange/CEP 9 SpectrumGreen probes showing marked heterozygous deletion of 9p21 with 2 signals for chromosome 9 (green) centromeric probe and only 1 signal for the 9p21 locus (orange). (A to C, Hematoxylin and eosin stain; original magnifications: A, 32.5; B, 340; C, 363.)

age. None of the clinical and morphologic parameters studied showed a significant correlation with the SLN status. Patients with atypical Spitz tumor were also grouped according to prepubertal versus pubertal age (# 11 years vs [11-18 years) and compared for clinicopathological findings, molecular features, and outcome but none of the morphomolecular parameters were found to significantly differ considering this age subgrouping. FISH analysis and statistical correlation between clinical/histopathological features and FISH Overall, FISH conventional melanoma probe analysis was found to be positive in 19 of 70 (27.1%) cases and specifically in 4 of 20 (20%) cases

classified as Spitz nevus and 15 of 50 (30%) as atypical Spitz tumors. Among all clinicopathological parameters studied, only nuclear pleomorphism and high nuclear-cytoplasmic ratio revealed a significant association with a conventional melanoma positive FISH analysis. Specifically, 18 of 19 (94.7%) and 12 of 19 (63.1%) FISH-positive cases were associated with these morphologic features (P = .02 and P = .01, respectively). FISH by 9p21 demonstrated homozygous deletion in 2 of 37 cases and heterozygous deletion in 3 of 37 cases. Of the 2 cases with 9p21 homozygous loss, 1 patient was alive and free of disease at 90 months whereas the other patient did not received SLNB procedure, but underwent an inguinal lymph node dissection showing in 2 enlarged lymph nodes small intracapsular and subcapsular deposits of atypical melanocytes and

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Table I. Summary of demographics, clinical findings, and outcome for Spitz nevus and atypical Spitz tumor

Age, y Range Mean Sex Male (41) Female (29) Site Head/neck Trunk Upper limb Lower limb Unknown Size, mm Range Mean Follow-up, mo Range Mean Progression No Yes Unknown FU NED DOD Lost SLNB Not performed Performed

Unknown

Spitz nevus, N = 20

Atypical Spitz tumor, N = 50

2-18 8.7

1-18 8.3

10 10

31 19

4 1 4 11

(20%) (5%) (20%) (55%) 0

2 5 16 26 1

(4%) (10%) (32%) (52%) (2%)

3-8 5.5

2.3-30 7.2

1-300 49.9

18-152 46.4

19 (95%) 0 1 (5%)

47 (94%) 2 (4%) 1 (2%)

19 (95%) 0 1 (5%)

48 (96%) 1 (2%) 1 (2%)

18 (90%) 1 (5%) 1: Negative

34 (68%) 15 (30%) 13: Negative 2: Micrometastasis 1 (2%)

1 (5%)

DOD, Dead of disease; NED, no evidence of disease; SLNB, sentinel lymph node biopsy.

no further evidence of disease was observed after 45 months. Of note, the primary tumor from the back of the right hand from the only fatal atypical Spitz tumor case showed heterozygous 9p21 deletion and MYB/CEP6 loss by conventional melanoma FISH. The subsequent right axillary lymph node metastasis showed CCND1 gain and RREB gain whereas a synchronous soft-tissue metastasis in the left buttocks did not reveal genetic abnormalities. None among all the clinical and morphologic variables analyzed revealed a significant association with 9p21 loss. In addition, no significant correlations were found between histopathological features and FISH considering FISH results as number of chromosomal alterations (ie, 1, 2, 3, 4, or 5 according

to CCD1, RREB1, MYB, CEP6, and 9p21 status) rather than absolute (negative vs positive).

DISCUSSION Our experience confirms that atypical Spitz tumor in pediatric age causes diagnostic difficulties. Upon revision, 34.9% of cases originally retrieved could not be properly requalified as cytologically Spitzoid, the majority of such cases being misinterpreted conventional melanomas with epithelioid or spindle cells. Thus, our results underscore the importance of a rigorous application of the cytologic diagnostic criteria that have been extensively described in the past to avoid misdiagnoses of serious clinical relevance.1-3 Although we acknowledge that the distinction among a Spitz nevus, atypical Spitz tumor, and Spitzoid melanoma is controversial and as such can be a matter of continuous debate, the determination as to what ‘‘Spitzoid’’ is and what it is not should be fairly less subjective. Although we agree that any lesion diagnosed as an atypical Spitz tumor in pediatric age should be evaluated by a dermatopathologist experienced with such lesions, action is required to reach larger consensus among general pathologists based on commonly shared cytologic criteria. In the current analysis, morphologic parameters that were significantly related with a diagnosis of atypical Spitz tumors over Spitz nevus included: asymmetry, level IV or V, lack of cytologic maturation, solid growth, nuclear pleomorphism, high nuclear-cytoplasmic ratio, both atypical and deep mitoses, and high mitotic rate. Such results are in line with previous observations but draw attention on a restricted number of criteria. Interestingly, in pediatric atypical Spitz tumors a direct correlation was found between mitotic rate and thickness (P = .03) whereas mitotic rate inversely correlated with age (P = .02). Thus, when evaluating the dermal mitotic rate in a Spitzoid lesion in pediatric age it is important to keep in mind that the threshold of less than 2 mitoses/mm2 favoring a diagnosis of Spitz nevus vs 2 to 6 mitoses/mm2 for atypical Spitz tumor should be interpreted with caution and in light of the age of the child. As previously indicated, external trauma and brisk inflammation may be also factors leading to higher mitotic rates.3 Because of the limited number of adverse events in our series we were not able to associate a meaningful prognostic significance to each of the morphologic atypical parameters observed in atypical Spitz tumors. Spatz et al4 in 1999 designed a scoring system for risk assessment in pediatric atypical Spitz tumors based on age, diameter, ulceration, subcutaneous fat involvement, and

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Table II. Distribution of histopathological features according to final diagnostic category (Spitz nevus vs atypical Spitz tumor) in patients aged 18 years or younger

Spitz nevus, N = 20

Mitotic rate \2/mm2 (n = 36) 2-6/mm2 (n = 28) [6/mm2 (n = 6) Deep mitoses Absent (n = 36) Present (n = 33) Not evaluable (n = 1) Atypical mitoses Absent (n = 46) Present (n = 24) Nuclear pleomorphism Absent (n = 15) Present (n = 54) Not evaluable (n = 1) High N/C ratio Absent (n = 56) Present (n = 14) Not evaluable (n = 1) Cytologic maturation Absent (n = 43) Present (n = 24) Not evaluable (n = 3) Asymmetry Absent (n = 32) Present (n = 28) Not evaluable (n = 10) Solid growth Absent (n = 49) Present (n = 21) Breslow thickness # 1 mm (n = 8) [1-2 mm (n = 22) [2 mm (n = 39) Not evaluable (n = 1) Clark level II (n = 2) III (n = 23) IV (n = 32) V (n = 10) Not evaluable (n = 3) Architecture Junctional (n = 1) Compound (n = 57) Dermal (n = 12) Peripheral pagetoidism Absent (n = 51) Present (n = 16) Not evaluable (n = 3)

Atypical Spitz tumor, N = 50

P

\.001 19 (95%) 1 (5%) 0 (0%)

17 (34%) 28 (56%) 5 (10%)

18 (90%) 2 (10%) 0 (0%)

18 (36%) 31 (62%) 1 (2%)

\.001

\.001 20 (100%) 0 (0%)

26 (52%) 24 (48%) \.001

10 (50%) 9 (45%) 1 (5%)

5 (10%) 45 (90%) 0 (0%)

17 (85%) 2 (10%) 1 (5%)

23 (46%) 27 (54%) 0 (0%)

6 (30%) 13 (65%) 1 (5%)

37 (74%) 11 (22%) 2 (4%)

15 (75%) 3 (15%) 2 (10%)

17 (34%) 25 (50%) 8 (16%)

19 (95%) 1 (5%)

30 (60%) 20 (40%)

.001

.001

.004

.004

.09 4 8 7 1

(20%) (40%) (35%) (5%)

4 14 32 0

(8%) (28%) (64%) (0%)

(10.0%) (25.0%) (55.0%) (0%) (10.0%)

0 18 21 10 1

(0%) (36%) (42%) (20%) (2%)

.01 2 5 11 0 2

.1 1 (5%) 17 (85%) 2 (10%)

0 (0%) 40 (80%) 10 (20%)

18 (90%) 2 (10%) 0 (0%)

33 (66%) 14 (28%) 3 (6%)

.1

Continued

Table II. Cont’d

Apoptosis Absent (n = 63) Present (n = 7) Architectural maturation Absent (n = 26) Present (n = 39) Not evaluable (n = 5) Desmoplasia Absent (n = 53) Present (n = 17) Cytotype Epithelioid (n = 10) Spindle (n = 31) Mixed (n = 29) Pushing deep border Absent (n = 53) Present (n = 15) Not evaluable (n = 2) Necrosis Absent (n = 67) Present (n = 3) Inflammatory infiltrate Absent (n = 33) Present (n = 37) Epidermal consumption Absent (n = 36) Present (n = 34) Circumscription Absent (n = 15) Present (n = 42) Not evaluable (n = 13) Ulceration Absent (n = 60) Present (n = 8) Not evaluable (n = 2) Prominent nucleoli Absent (n = 17) Present (n = 53) Plasma cells Absent (n = 68) Present (n = 2)

Spitz nevus, N = 20

Atypical Spitz tumor, N = 50

20 (100%) 0 (0%)

43 (86%) 7 (14%)

4 (20%) 15 (75%) 1 (5%)

20 (40%) 26 (52%) 4 (8%)

13 (65%) 7 (35%)

40 (80%) 10 (20%)

4 (20%) 7 (35%) 9 (45%)

6 (12%) 24 (48%) 20 (40%)

17 (85%) 3 (15%) 0 (0%)

36 (72%) 12 (24%) 2 (4%)

20 (100%) 0 (0%)

47 (94%) 3 (6%)

10 (50%) 10 (50%)

23 (46%) 27 (54%)

11 (55%) 9 (45%)

25 (50%) 25 (50%)

4 (20%) 15 (75%) 1 (5%)

11 (22%) 27 (54%) 12 (24%)

18 (90%) 2 (10%) 0 (0%)

42 (84%) 6 (12%) 2 (4%)

5 (25%) 15 (75%)

12 (24%) 38 (76%)

20 (100%) 0 (0%)

48 (96%) 2 (4%)

P

.1

.1

.2

.5

.5

.5

.7

.7

.7

1

1

1

mitotic activity but such system has not been fully validated. The search of morphologic parameters that may carry prognostic information in atypical Spitz tumor, irrespective of age, has been in the last decades a restless and hitherto ineffective effort. Cerroni et al29 emphasized the importance of increased mitotic activity, mitoses near the base, and a greater degree of inflammation for recognition of lesions with unfavorable behavior. More recently, the histomorphologic features that most correlated

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Table III. Distribution of histopathological features in atypical Spitz tumor subgroup, according to patient’s age Age # 14 years, N = 43

Clark level III (n = 18) IV (n = 21) V (n = 10) Not evaluable (n = 1) Mitotic rate/mm2 \2/mm2 (n = 17) 2-6/mm2 (n = 28) [6/mm2 (n = 5) Prominent nucleoli Absent (n = 12) Present (n = 38) Desmoplasia Absent (n = 40) Present (n = 10) Pushing deep border Absent (n = 36) Present (n = 12) Not evaluable (n = 2) Solid growth Absent (n = 30) Present (n = 20) Cytological maturation Absent (n = 37) Present (n = 11) Not evaluable (n = 2) Cytotype Epithelioid (n = 6) Spindle (n = 24) Mixed (n = 20) Breslow # 1 mm (n = 4) 1-2 mm (n = 14) [2 mm (n = 32)

Age [ 14 years, N=7

P

.04 17 15 10 1

(40%) (35%) (23%) (2%)

1 6 0 0

(14%) (86%) (0%) (0%) .04

17 (39%) 21 (49%) 5 (12%)

0 (0%) 7 (100%) 0 (0%)

12 (28%) 31 (72%)

0 (0%) 7 (100%)

36 (84%) 7 (16%)

4 (57%) 3 (43%)

29 (67%) 12 (28%) 2 (5%)

7 (100%) 0 (0%) 0 (0%)

24 (56%) 19 (44%)

6 (86%) 1 (14%)

33 (77%) 8 (18%) 2 (5%)

4 (57%) 3 (43%) 0 (0%)

6 (14%) 19 (44%) 18 (42%)

0 (0%) 5 (72%) 2 (28%)

4 (9%) 13 (30%) 26 (61%)

0 (0%) 1 (14%) 6 (86%)

.1

.1

.1

.2

.3

.3

.4

with disease progression in atypical Spitz tumor were: frequent mitoses, deep mitoses, asymmetry, high-grade cytologic atypia, and ulceration.6 Death caused by conventional melanoma is uncommon in children of all ages, particularly for the prepubescent ones.30-33 It has been observed that melanomas that occur in patients younger than 11 years have a more favorable prognosis and a less aggressive behavior than those detected in pubescent children and adults (age [11 years).32,34 In our study, however, categorization at 11 years failed to demonstrate significant differences in morphomolecular features. We herein confirm previous observations that children and teenagers with atypical Spitz tumor

tend to have a favorable prognosis, even in presence of a positive SLN.19 In line with our findings, it has been reported that the mortality rate in patients with atypical Spitz tumor is presumably less than 5%.26 Several studies emphasized that despite the presence of SLN metastases (ranging from 16%-50%), patients with atypical Spitz tumor almost always fare well18-26,29,35-42 although rare fatal cases have been documented.21,29,40 Therefore, the predictive value of SLN in patients with atypical Spitz tumor is limited and significantly different from that for conventional melanoma.26,42,43 In pediatric age, technical feasibility of SLNB has been verified but the significance and use of SLNB to potentially aid in the proper management has been partly reconsidered.44,45 Younger patients show a greater proportion of nodal micrometastases that are clinically irrelevant, and a more competent immune system able to eliminate deposits and further dissemination has been advocated.46-49 In our study, the 4-probe FISH melanoma assay did not discriminate atypical Spitz tumor from Spitz nevi. Thus, in unequivocal Spitz nevi caution should be taken if the FISH test result is positive and FISH positivity should not lead to modifying the patient’s treatment, although it should be emphasized that not all the changes are of equal value and that certain aberrations may be more significant than others and increasing aneuploidy/genetic complexity has been correlated with a more adverse outcome.28 Of note, an important finding of the current study was that 2 of 37 atypical Spitz tumor cases had homozygous deletion of 9p21 and in one of them atypical melanocytes were found in 2 inguinal lymph nodes (SLN not performed). Interestingly, the primary tumor from the only fatal atypical Spitz tumor case showed genetic abnormalities by conventional FISH analysis and heterozygous 9p21 loss. A recent study has reported that the prognosis for patients with atypical Spitz tumor and heterozygous 9p21 deletion is significantly better than those with homozygous deletion of 9p21.50 The fact that in our fatal case heterozygous 9p21 loss was not the only genetic aberration may be a plausible explanation for the adverse clinical outcome. In addition, it has been previously hypothesized that an atypical Spitz tumor with heterozygous 9p21 deletions could continue proliferating and by clonal selection eventually develop homozygous 9p21 deletions.50 In conclusion, in children and teenagers caution is needed to avoid overdiagnosis of atypical Spitz tumor rather than Spitz nevus and to misdiagnose a conventional melanoma with epithelioid or spindle cells as atypical Spitz tumor. Pediatric atypical Spitz

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tumors seem to be associated with minimal lethal potential. Nevertheless, the only case in our series that had a lethal outcome, although associated with en masse in necrosis in the lymph nodal metastasis (a rare finding in atypical Spitz tumor), did not show unequivocal melanoma features in the primary lesion and was retrospectively classified by experienced pathologists as atypical Spitz tumor or Spitzoid tumor with uncertain biological potential. This underlines the need for great care when dealing with Spitzoid lesions that show any degree of deviation from the classic features of Spitz nevus. Although we are still unable to suggest objective guidelines for the optimal treatment of these patients, complete excision with clear margins and careful follow-up are strictly recommended. Caution should be exercised in extrapolating atypical Spitz tumors’ management in adult patients to pediatric age and our data do not support any clinical benefit for SLNB procedure and completion lymphadenectomy.

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