Spitz Nevi, Atypical Spitzoid Neoplasms, and Spitzoid Melanoma

Mechanisms of tropomyosin 3 in the development of malignant tumors

Tropomyosin (TPM) is an important regulatory protein that binds to actin in fine myofilaments, playing a crucial role in the regulation of muscle contraction. TPM3, as one of four tropomyosin genes, is notably prevalent in eukaryotic cells. Traditionally, abnormal gene expression of TPM3 has been exclusively associated with myopathy. However, recent years have witnessed a surge in studies highlighting the close correlation between abnormal expression of TPM3 and the onset, progression, metastasis, and prognosis of various malignant tumors. In light of this, investigating the mechanisms underlying the pathogenetic role of TPM3 holds significant promise for early diagnosis and more effective treatment strategies. This article aims to provide an insightful review of the structural characteristics of TPM3 and its intricate role in the occurrence and development of malignant tumors.

Spitz Tumor With SQSTM1::NTRK2 Fusion: A Clinicopathological Study of 5 Cases

ABSTRACT

Spitz tumors are melanocytic neoplasms characterized by specific, mutually exclusive driver molecular events, namely genomic rearrangements involving the threonine kinase BRAF and the tyrosine kinase receptors ALK , NTRK1 , NTRK2 , NTRK3 , MET , RET , ROS1 , and MAP3K8 or less commonly, mutations in HRAS or MAP2K1 . We hereby report 5 Spitz tumors with a SQSTM1::NTRK2 fusion. All patients were woman with the ages at diagnosis ranging from 30 to 50 years. Locations included the lower extremity (n = 3), forearm, and back (one each). All the neoplasms were superficial melanocytic proliferation with a flat to dome-shaped silhouette, in which junctional spindled and polygonal dendritic melanocytes were mainly arranged as horizontal nests associated with conspicuous lentiginous involvement of the follicular epithelium. Only one case showed heavily pigmented, vertically oriented melanocytic nests resembling Reed nevus. A superficial intradermal component observed in 2 cases appeared as small nests with a back-to-back configuration. In all lesions, next-generation sequencing analysis identified a SQSTM1::NTRK2 fusion. A single case studied with fluorescence in situ hybridization for copy number changes in melanoma-related genes proved negative. No further molecular alterations were detected, including TERT-p hotspot mutations.

Histopathologic and Molecular Diagnosis of Melanoma

Conventional histopathology is the primary means of melanoma diagnosis. Both architectural and cytologic features aid in discrimination of melanocytic nevi from melanoma. Communication between the clinician and pathologist regarding the history, examination, differential diagnosis, prior biopsy findings, method of sampling, and specimen orientation is critical to an accurate diagnosis. A melanoma pathology report includes multiple prognostic indicators to guide surgical and medical management. In challenging cases, immunohistochemistry and molecular diagnostics may be of benefit.

Standardized diagnostic algorithm for spitzoid lesions aids clinical decision-making and management: a case series from a Swiss reference center

Importance: Spitzoid lesions are a group of melanocytic tumors characterized by spindle-like or epithelioid cells with variable malignant potential. While some spitzoid lesions are classified as evidently benign or malignant by clinic and histology, others present with unclear clinical and histological characteristics and are categorized as lesions of intermediate biologic potential. These lesions represent a challenge for pathologists and clinicians alike. No consensus on ancillary diagnostics and clinical management exists. Prediction of their clinical course is difficult. The implementation of ancillary diagnostics is currently subject of extensive discussions.

Observations: We report three cases of spitzoid lesions in three young female patients (3-, 15- and 17 years old) from a single reference center with different clinical and histological manifestations. In each case, uncertain clinical and histological presentation led to the stepwise application of additional diagnostics using immunohistochemistry and a custom next generation sequencing panel optimized for melanocytic lesions (MelArray). Combining ancillary diagnostics helped determine clinical management in all cases by characterizing the biology of these lesions.

Conclusions and Relevance: We illustrate how clinical, histological and molecular features contribute to an optimized management plan in these critical situations and present a possible algorithm for the assessment of spitzoid neoplasms.

Spitz Tumors With ROS1 Fusions: A Clinicopathological Study of 6 Cases, Including FISH for Chromosomal Copy Number Alterations and Mutation Analysis Using Next-Generation Sequencing

Spitz tumors represent a heterogeneous group of melanocytic neoplasms with a spectrum of biological behavior ranging from benign (Spitz nevus) to malignant (spitzoid melanoma). Prediction of the behavior of these lesions based on their histological presentation is not always possible. Recently, mutually exclusive activating kinase fusions, involving ALK, NTRK1, NTRK3, RET, MET, ROS1, and BRAF, have been found in a subset of spitzoid lesions. Some of these genetic alterations were associated with specific morphological features. Here, we report the histological presentation of 6 Spitz tumors with ROS1 fusion. The age of the patients ranged from 6 to 34 years, with strong female prevalence (5:1). All neoplasms were compound melanocytic proliferations with a predominant dermal growth but a conspicuous junctional component displaying atypical microscopic features qualifying them as atypical Spitz tumor. FIP1L1 and CAPRIN1 were identified as 2 novel 5'-fusion partners of ROS1 along with the known PWWP2A-ROS1 fusion. FISH for copy number changes of 9p21, 6p25, and 11q13 was negative in all but 1 neoplasm harboring isolated gain of 8q24. TERT-promoter hotspot mutation analysis was negative in all tumors. All patients are disease-free after a mean follow-up period of 30 months. It is concluded that ROS1-fused spitzoid neoplasms seem to have no distinctive histopathological features although consistent findings were spindled melanocytes arranged in confluent whorling nests, prominent transepidermal elimination of melanocytic nests, and myxoid/mucinous changes.

ALK-positive compound Spitz nevus with extensive perineural and intraneural neurotropism

Historically recognized by their characteristic histopathologic features, Spitz neoplasms are now known to be molecularly defined by mutually exclusive recurrent abnormalities that cause activation of the MAPK pathway. Spitz neoplasms with ALK rearrangements frequently demonstrate polypoid growth with a plexiform arrangement of nested, fusiform melanocytes in intersecting fascicles. Although neurotropism has been described in indolent Spitz neoplasms, this feature is not frequently mentioned in publications on histopathologic assessment of this group of melanocytic tumors. Here, we present an unusual case of a 3-year-old female with an ALK-positive compound Spitz nevus with extensive perineural and intraneural neurotropism occurring on the vermilion border of the lower lip.

A sixteen-year single-center retrospective chart review of Spitz nevi and spitzoid neoplasms in pediatric patients

BACKGROUND

Spitzoid neoplasms in pediatric patients pose an interesting challenge for clinicians. More data on the clinical, histologic, and molecular characteristics of these lesions are necessary to distinguish features that may portend recurrence or malignant behavior to help determine future treatment guidelines in pediatric patients.

METHODS

Institutional Review Board approval was obtained from Children's Hospital of Wisconsin to conduct a retrospective analysis of spitzoid neoplasms. Patients with biopsied or excised spitzoid neoplasms between 01/01/2000 and 08/01/2016 were included. Pertinent clinical and histologic data were collected. Atypical, unusual, or diagnostically uncertain lesions were selected for re-review.

RESULTS

266 lesions from 264 patients were included. 243 were classified as benign (91.35%), 22 as atypical (8.27%), and 1 as spitzoid melanoma (0.38%). No clinical or histologic variables were found to be statistically significant between the benign Spitz, atypical Spitz, and spitzoid melanoma cohorts. No known deaths occurred.

CONCLUSION

Our findings highlight the extreme variability of spitzoid neoplasms clinically and histologically. Importantly, this study demonstrates that the vast majority of spitzoid neoplasms in pediatric populations are benign and supports conservative management of spitzoid lesions in children.

A Clinicopathological Study of 29 Spitzoid Melanocytic Lesions With ALK Fusions, Including Novel Fusion Variants, Accompanied by Fluorescence In Situ Hybridization Analysis for Chromosomal Copy Number Changes, and Both TERT Promoter and Next-Generation Sequencing Mutation Analysis

ALK-fused spitzoid neoplasms represent a distinctive group of melanocytic lesions. To date, few studies addressed genetic and chromosomal alterations in these lesions beyond the ALK rearrangements. Our objective was to study genetic alterations, including ALK gene fusions, telomerase reverse transcriptase promoter (TERT-p) mutations, chromosomal copy number changes, and mutations in other genes. We investigated 29 cases of Spitz lesions (11 Spitz nevi and 18 atypical Spitz tumors), all of which were ALK immunopositive. There were 16 female and 13 male patients, with age ranging from 1 to 43 years (mean, 18.4 years). The most common location was the lower extremity. Microscopically, all neoplasms were polypoid or dome shaped with a plexiform, predominantly dermally located proliferation of fusiform to spindled melanocytes with mild to moderate pleomorphism. The break-apart test for ALK was positive in 17 of 19 studied cases. ALK fusions were detected in 23 of 26 analyzable cases by Archer FusionPlex Solid Tumor Kit. In addition to the previously described rearrangements, 3 novel fusions, namely, KANK1-ALK, MYO5A-ALK, and EEF2-ALK, were found. Fluorescence in situ hybridization for copy number changes yielded one case with the loss of RREB1 among 21 studied cases. TERT-p hotspot mutation was found in 1 of 23 lesions. The mutation analysis of 271 cancer-related genes using Human Comprehensive Cancer Panel was performed in 4 cases and identified in each case mutations in several genes with unknown significance, except for a pathogenic variant in the BLM gene. Our study confirms that most ALK fusion spitzoid neoplasms can be classified as atypical Spitz tumors, which occurs in young patients with acral predilection and extends the spectrum of ALK fusions in spitzoid lesions, including 3 hitherto unreported fusions. TERT-p mutations and chromosomal copy number changes involving 6p25 (RRB1), 11q13 (CCND1), 6p23 (MYB), 9p21 (CDKN2A), and 8q24 (MYC) are rare in these lesions. The significance of mutation in other genes remains unknown.

Expression of p15 in a spectrum of spitzoid melanocytic neoplasms

BACKGROUND

Accurate classification of spitzoid melanocytic lesions is difficult due to overlapping clinical and histopathologic features between Spitz nevi, atypical Spitz tumors (ASTs), and spitzoid melanomas. Expression of p16 (CDKN2A) has been used as a marker of spitzoid lesions. However, its expression may be variable. p15 is a tumor suppressor encoded by CDKN2B, loss of which has been recently shown to promote transition from nevus to melanoma. We sought to determine whether p15 is a useful immunohistochemical marker to distinguish Spitz nevi from spitzoid melanomas and to compare p15 and p16 staining in this population.

METHODS

Immunohistochemistry for p15 and p16 was performed on Spitz nevi (n = 19), ASTs (n = 41), and spitzoid melanomas (n = 17). Immunoexpression was categorized by a four-tiered system: 0 (negative), 1+ (weak), 2+ (moderate), 3+ (strong).

RESULTS

3+/strong p15 staining was observed in 68.4% of Spitz nevi, 34.2% of ASTs, and 17.7% of spitzoid melanomas. By contrast, we observed 3+ p16 staining in roughly equivalent percentages of Spitz nevi (57.9%), ASTs (56.1%), and spitzoid melanomas (58.8%).

CONCLUSION

These data illustrate that p15 may be more useful than p16 as a biomarker to help distinguish benign from malignant spitzoid lesions.

The role of routine imaging in pediatric cutaneous melanoma

BACKGROUND

Optimal imaging for children with pediatric malignant melanoma (MM) is unknown.

METHODS

We reviewed clinical and imaging findings of patients with American Joint Commission on Cancer (AJCC) stage IIC-IV MM treated on our institutional MEL06 trial. All patients had baseline brain magnetic resonance imaging/computed tomography (MRI/CT), positron emission tomography/computed tomography (PET/CT), CT chest, abdomen, and pelvis (CTCAP). Patients on stratum A (PEG-interferon, where PEG is pegylated; AJCC IIC, IIIA, IIIB; n = 16) had imaging every 6 months; stratum B1 (PEG-interferon and temozolomide; unresectable measurable disease, metastatic, or recurrent; n = 2) had PET/CT scans every 2 months and brain imaging studies every 4 months; stratum B2 patients (PEG-interferon and temozolomide; unresectable nonmeasurable, metastatic, or recurrent, n = 3) had imaging every 4 months. Off-therapy imaging was done every 6 months for 3 years.

RESULTS

There were 21 patients (11 females, 11 spitzoid, median age 14 years, head/neck [6], trunk [7], extremities [8]). Patients with spitzoid melanoma underwent 236 imaging studies in total (86 PET/CT, 81 CTCAP, 11 CT chest, 10 CT brain, 48 MRI brain) at a median cost per patient of $32,718. Thirteen studies (5.8%) had findings that led to two biopsies (one positive). For conventional MM, 162 studies (61 PET/CT, 57 CTCAP, 8 CT chest, 7 CT brain, and 29 MRI brain) were performed with a median cost per patient of $23,420. Twenty (14%) had findings leading to six biopsies (four positive). At 6.3 years (range 0.4-9.2), 17 patients remain disease-free.

CONCLUSION

Children with spitzoid melanoma require minimal imaging at diagnosis and follow-up. Patients with conventional MM should be imaged according to adult guidelines.

Paediatric melanoma

Paediatric melanoma, although rare, is the most common skin cancer in children. Our current knowledge on paediatric melanoma incidence trends is expanding, as several studies have addressed this issue with conflicting results. Known risk factors for paediatric melanoma include family history of melanoma, a previous history of malignancy, large congenital nevi, numerous melanocytic nevi, sunburns, increased UV exposure and a sun-sensitive phenotype. In younger children, melanoma more often presents with atypical features, such as a changing, amelanotic or uniformly coloured, often bleeding lesion, not fulfilling in most cases the conventional ABCDE criteria. The major differential diagnoses are melanocytic nevi, proliferative nodules in congenital nevi and atypical Spitz tumours. Moreover, in the younger age group non-Caucasian children are over-represented, tumours tend to be thicker and lymph nodes are often involved. Despite the frequent diagnosis at an advanced stage, the overall survival is fair in paediatric melanoma. Specific guidelines for management of melanoma in children do not exist, and most often the disease is treated similarly to melanoma in adults.

Protein gene product 9.5 (PGP9.5) expression in benign cutaneous mesenchymal, histiocytic, and melanocytic lesions: comparison with cellular neurothekeoma

Cellular neurothekeoma (CNTK) frequently enters the differential diagnosis of a benign dermal cellular proliferation. Diagnosis often relies on immunohistochemistry including the use of protein gene product 9.5 (PGP9.5). A previous study demonstrated PGP9.5 expression across a wide variety of soft tissue neoplasms. We explored the utility of this antibody in distinguishing CNTK from other benign dermal-based lesions. A cohort of CNTK (n=7) and benign cutaneous lesions of neural (n=28), fibrohistiocytic (n=23), fibroblastic (n=25), histiocytic (n=18), myofibroblastic (n=7), smooth muscle (n=14), and melanocytic (n=12) differentiations were immunostained with PGP9.5. Staining was graded by H-score and compared with CNTK. A significantly higher H-score was found in CNTK compared with the fibrohistiocytic (p=0.0001), histiocytic (p=0.0016), myofibroblastic (p=0.0003), smooth muscle (p<0.0001), and melanocytic (p=0.0004) groups, with the exceptions of plexiform fibrohistiocytic tumour, xanthoma, and xanthogranuloma. No significant difference was found when comparing CNTK with fibroblastic and neural lesions, with the exceptions of neurofibroma and perineurioma. In conclusion, PGP9.5 is helpful in distinguishing CNTK from most benign cutaneous fibrohistiocytic, histiocytic, myofibroblastic, smooth muscle, and melanocytic lesions. In addition to CNTK and neural lesions, PGP9.5 is also expressed in benign fibroblastic lesions, and therefore distinction of these lesions should not be based on PGP9.5 positivity.

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.

Imaging mass spectrometry assists in the classification of diagnostically challenging atypical Spitzoid neoplasms

BACKGROUND

Previously, using imaging mass spectrometry (IMS), we discovered proteomic differences between Spitz nevi and Spitzoid melanomas.

OBJECTIVE

We sought to determine whether IMS can assist in the classification of diagnostically challenging atypical Spitzoid neoplasms (ASN), to compare and correlate the IMS and histopathological diagnoses with clinical behavior.

METHODS

We conducted a retrospective collaborative study involving centers from 11 countries and 11 US institutions analyzing 102 ASNs by IMS. Patients were divided into clinical groups 1 to 4 representing best to worst clinical behavior. The association among IMS findings, histopathological diagnoses, and clinical groups was assessed.

RESULTS

There was a strong association between a diagnosis of Spitzoid melanoma by IMS and lesions categorized as clinical groups 2, 3, and 4 (recurrence of disease, metastases, or death) compared with clinical group 1 (no recurrence or metastasis beyond a sentinel node) (P < .0001). Older age and greater tumor thickness were strongly associated with poorer outcome (P = .01).

CONCLUSIONS

IMS diagnosis of ASN better predicted clinical outcome than histopathology. Diagnosis of Spitzoid melanoma by IMS was strongly associated with aggressive clinical behavior. IMS analysis using a proteomic signature may improve the diagnosis and prediction of outcome/risk stratification for patients with ASN.

Cutaneous syncytial myoepithelioma:: Clinico-pathological features and differential diagnosis

Cutaneous syncytial myoepithelioma (CSM) is a very rare tumor belonging to the spectrum of skin myoepithelial lesions. CSM usually affects the upper extremities of young to middle aged patients and is characterized by peculiar morphological and immunohistochemical features. Unlike classic myoepithelioma, CSM is composed by a densely packed proliferation of spindled to histiocytoid cells, which are variably positive for EMA, S100, SMA, and frequently negative for cytokeratins and GFAP. The peculiar histopathology and the extreme rarity of such lesion (less than 40 cases reported in the literature) can make the diagnosis of CSM a true challenge. In the present case, we report the clinico-pathological features of a primary CSM occurring in a 38 year-old Caucasian man. The differential diagnoses of such lesion are also briefly discussed.

Global microRNA profiling for diagnostic appraisal of melanocytic Spitz tumors

BACKGROUND

Melanoma skin cancer remains the leading cause of skin cancer-related deaths. Spitz lesions represent a subset of melanocytic skin lesions characterized by epithelioid or spindled melanocytes organized in nests. These lesions occupy a spectrum ranging from benign Spitz and atypical Spitz lesions all the way to malignant Spitz tumors. Appropriate management is reliant on accurate diagnostic classification, yet this effort remains challenging using current light microscopic techniques. The discovery of novel biomarkers such as microRNAs (miR) may ultimately be a useful diagnostic adjunct for the evaluation of Spitz lesions. miR expression profiles have been suggested for non-Spitz melanomas but have yet to be ascribed to Spitz lesions. We hypothesized that distinct miR expression profiles would be associated with different lesions along the Spitz spectrum.

MATERIALS AND METHODS

RNAs extracted from paraffin-embedded, formalin-fixed tissues of 11 resected skin lesions including benign nevi (n = 2), benign Spitz lesions (n = 3), atypical Spitz lesions (n = 3), and malignant Spitz tumors (n = 3) were analyzed by the NanoString platform for simultaneous evaluation of over 800 miRs in each patient sample.

RESULTS

Benign Spitz lesions had increased expression of miR-21-5p and miR-363-3p compared with those of benign nevi. Malignant Spitz lesions exhibited overexpression of miR-21-5p, miR-155-5p, and miR-1283 relative to both benign nevi and benign Spitz tumors. Notably, atypical Spitz tumors had increased expression of miR-451a and decreased expression of miR-155-5p expression relative to malignant Spitz lesions. Conversely, atypical Spitz lesions had increased expression of miR-21-5p, miR-34a-5p, miR-451a, miR-1283, and miR-1260a relative to benign Spitz tumors.

CONCLUSIONS

Overall, distinct miR profiles are suggested among Spitz lesions of varying malignant potential with some similarities to non-Spitz melanoma tumors. This work demonstrates the feasibility of this analytic method and forms the basis for further validation studies.

Selected benign cutaneous lesions that may simulate melanoma histologically

As cutaneous melanomas manifest a wide spectrum of clinical and pathologic presentations, several other lesions enter into their differential diagnosis. This article considers those entities, including melanocytic hyperplasia, cellular nodules in congenital nevi, atypical lentiginous melanocytic proliferations, "special site" nevi, epithelioid histiocytoma, neurothekeoma, cellular schwannoma, and proliferating scars.

Spitz Tumors

Spitz tumors are a group of melanocytic neoplasms with distinct morphological features that tend to affect young individuals. Distinguishing benign from malignant Spitz tumors can be challenging, but cytogenetic and molecular tests have contributed to improvements in diagnostic accuracy. Spitz tumors harbor diverse genetic alterations, including mutations in HRAS, loss of BAP1, or kinase fusions in ROS1, NTRK1, ALK, BRAF, and RET genes. Limited data exist on the correlation between histopathological features and kinase fusions. Here, we describe the histopathological features of 105 Spitz tumors (Spitz nevi and atypical Spitz tumors), comparing lesions according to their immunoreactivity for ALK or NTRK1. Intersecting fascicular growth of fusiform melanocytes was seen in all but one ALK-positive tumor (27 of 28 or 96.4%), whereas it was infrequent in NTRK1-positive tumors (5 of 20 or 25.0%) and tumors negative for both ALK and NTRK1 (96.4% vs 25.0% vs 8.7%, P < .0027). There was a trend toward ALK-positive tumors being amelanotic compared with NTRK1-positive tumors and combined ALK-/NTRK1-negative tumors (89.3% vs 45% vs 47.4%, respectively, P = .1023) and lacking epithelioid cell morphology (0% vs 45.0% vs 41%, respectively, P = .6985). In conclusion, this study confirms that although not specific, the growth pattern of intersecting fascicles of amelanotic fusiform melanocytes is strongly associated with ALK expression.

Atypical Spitz Tumors: A Diagnostic Challenge

Spitzoid melanocytic lesions encompass a spectrum from benign Spitz nevi to malignant spitzoid melanomas. Spitzoid melanocytic neoplasms have significant morphologic and molecular differences from conventional melanocytic lesions, and prediction of biologic behavior and metastatic risk may be difficult. Most challenging is the atypical Spitz tumor, a borderline spitzoid melanocytic lesion of uncertain malignant potential that has overlapping histologic features with conventional Spitz nevus and spitzoid melanoma. Atypical Spitz tumors involve the sentinel lymph nodes at a greater frequency than conventional melanoma and frequently harbor chromosomal copy number changes, yet most cases follow an indolent course. Herein we review the clinical, microscopic, and molecular features of atypical Spitz tumors, including recent molecular advances, including the potential prognostic significance of chromosomal abnormalities, such as homozygous CDKN2A loss.

Pump-probe imaging of pigmented cutaneous melanoma primary lesions gives insight into metastatic potential

Metastatic melanoma is associated with a poor prognosis, but no method reliably predicts which melanomas of a given stage will ultimately metastasize and which will not. While sentinel lymph node biopsy (SLNB) has emerged as the most powerful predictor of metastatic disease, the majority of people dying from metastatic melanoma still have a negative SLNB. Here we analyze pump-probe microscopy images of thin biopsy slides of primary melanomas to assess their metastatic potential. Pump-probe microscopy reveals detailed chemical information of melanin with subcellular spatial resolution. Quantification of the molecular signatures without reference standards is achieved using a geometrical representation of principal component analysis. Melanin structure is analyzed in unison with the chemical information by applying principles of mathematical morphology. Results show that melanin in metastatic primary lesions has lower chemical diversity than non-metastatic primary lesions, and contains two distinct phenotypes that are indicative of aggressive disease. Further, the mathematical morphology analysis reveals melanin in metastatic primary lesions has a distinct "dusty" quality. Finally, a statistical analysis shows that the combination of the chemical information with spatial structures predicts metastatic potential with much better sensitivity than SLNB and high specificity, suggesting pump-probe microscopy can be an important tool to help predict the metastatic potential of melanomas.

Case reports of fatal or metastasizing melanoma in children and adolescents: a systematic analysis of the literature

Childhood melanoma (ChM) is rare, with clinical and epidemiologic characteristics that differ from those of adult melanomas. The objective of the current study was to systematically identify and analyze case reports and case series of fatal and metastasizing ChM in the medical literature. ChM case reports with a fatal outcome or metastases were identified using a Medline search and subdivided into ChM developing in the absence of a congenital melanocytic nevus (ChM without CMN) and ChM associated with a CMN (ChM with CMN); 258 cases of ChM without CMN (206 cutaneous, 52 noncutaneous) were identified. In cutaneous ChM without CMN with a fatal outcome (n = 155), the mean age at diagnosis was 13.1 years (median 14 yrs). The mean Breslow index in this group was 8.5 mm for children ages 0 to 10 years and 3.7 mm for children ages 11 to 18 years. In ChM with CMN (n = 178; 112 cutaneous, 66 central nervous system [CNS]), the mean age at diagnosis was 5.8 years for cutaneous melanoma (median 3 yrs) and 5.5 years for CMN-associated CNS melanoma (median 3 yrs). The majority of CMN-associated cutaneous melanomas developed in small and giant CMN (vs medium and large); 53.9% of CNS melanomas developed in patients with multiple medium CMN. This study represents the largest and most complete synopsis of ChM case reports in the medical literature. Our analysis supports the view that cutaneous ChM without CMN (or associated with smaller CMN) differs in several important aspects from ChM associated with large or giant CMN.

Atypical Spitz tumors in patients younger than 18 years

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/mm(2). 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.

The deep penetrating nevus

The deep penetrating nevus (DPN), also known as the plexiform spindle cell nevus, is a pigmented lesion that commonly arises on the head and neck in the first few decades of life. Histopathologically, the DPN is wedge-shaped and contains melanocytes that exhibit deep infiltration into the dermis. Given these features, DPN may clinically and histopathologically mimic malignant melanoma, sparking confusion about the appropriate evaluation and management of these lesions. The goal of this review is to summarize the clinical and histopathological features of DPN and to discuss diagnostic and treatment strategies for dermatologists.

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.

Controversies in the evaluation and management of atypical melanocytic proliferations in children, adolescents, and young adults

The rising incidence of melanoma in children has brought increased attention to the clinical and pathologic diagnosis of pigmented lesions in the pediatric age group. Although melanoma in infancy and early childhood is often associated with large congenital nevi, in older children and teenagers it is most often sporadic, occurring in patients with a low skin phototype and substantial sun exposure. The rarity of this potentially fatal disorder demands astute clinical attention and a high index of suspicion for atypical lesions in pediatric patients. The challenges include the difficult decision of whether to biopsy and an often equivocal pathologic diagnosis. These diagnostically challenging and equivocal lesions lead to a degree of uncertainty regarding additional workup, prognosis, potential therapy, and follow-up plans. Consultation with a specialty dermatopathologist can be very helpful, and advanced molecular diagnostic techniques may be used in selected circumstances. Although still controversial, good evidence exists to justify a role for sentinel lymph node biopsy. Patients with atypical melanocytic proliferations have a high rate of positive sentinel lymph nodes; however, their outcomes are clearly better than in similarly staged adults with conventional melanoma. With the multiple variables involved and the relative lack of prospectively derived evidence, clinical decision-making is challenging and patients and families may experience considerable stress. This article provides data and weighs the pros and cons of a rationale for decision-making in pediatric and young adult patients with diagnostically challenging melanocytic lesions.

Spitzoid melanoma in a child with Li-Fraumeni syndrome

Spitzoid melanoma of childhood is a rare malignancy. The histological features are at the upper end of a range encompassing Spitz nevus and atypical Spitz tumor, the unifying features including large oval, fusiform or polygonal melanocytes with abundant homogeneous-appearing cytoplasma and large vesicular nuclei. The presence of a "bottom-heavy" pattern, strikingly enlarged nuclei and nucleoli in both the upper and lower portions of the lesion, and deep mitotic figures are among the findings that distinguish most of the Spitzoid melanomas from Spitz nevi and atypical Spitz tumors. There are no syndromic associations reported for this malignancy. We report the occurrence of choroid plexus carcinoma, Spitzoid melanoma, and myelodysplasia in a child who was found to carry a germline mutation for TP53. While choroid plexus carcinoma and myelodysplasia have relatively frequently been described, melanomas have been very rarely described in Li-Fraumeni syndrome. The association of Spitzoid melanoma with Li-Fraumeni syndrome, especially in a pediatric patient, has not been reported before.

Integrating molecular biomarkers into current clinical management in melanoma

Personalized melanoma medicine has progressed from histopathologic features to serum markers to molecular profiles. Since the identification of activating BRAF mutations and subsequent development of drugs targeting the mutant BRAF protein, oncologists now need to incorporate prognostic and predictive biomarkers into treatment decisions for their melanoma patients. Examples include subgrouping patients by genotype profiles for targeted therapy and the development of serologic, immunohistochemical, and genotype profiles for the selection of patients for immunotherapies. In this chapter, we provide an overview of the current status of BRAF mutation testing, as well as promising serologic and molecular profiles that will impact patient care. As further research helps clarify the roles of these factors, the clinical outcomes of melanoma patients promise to be greatly improved.

Intraoral Spitz nevus: case report and literature review

Spitz nevi account for approximately 1% of all melanocytic nevi of the skin in children. Although Spitz nevi often develop in the skin of the head and neck, intraoral Spitz nevi are rare. These nevi contain epithelioid and spindle cells and exhibit cytologic and architectural atypia when compared with routine melanocytic nevi, and may be mistaken for atypical Spitz tumor, Spitzoid melanoma, or conventional melanoma. Here, we report a Spitz nevus on the buccal mucosa of an 11-year-old boy. The tumor was composed of a proliferation of mostly epithelioid melanocytes with a smaller spindle cell component. The melanocytes were positive for S100, MART-1, and p16 proteins, with HMB-45-positive cells located only in the basal cell layer and superficial lamina propria. Less than 5% of the nuclei were positive for MIB-1, and there were no mitotic figures. We review the literature on 7 previously reported cases of Spitz nevi.

9p21 gene locus in Spitz nevi of older individuals: absence of cytogenetic and immunohistochemical findings associated with malignancy

The diagnosis of Spitz nevus in an elderly individual is often met with skepticism because the lesion can be difficult to distinguish from melanoma and because the probability of a malignant melanoma is higher in older patients. Recently, increased sensitivity for detection of malignant spitzoid neoplasms using 9p21 fluorescence in situ hybridization (FISH) has been described. In this study, we address the question of whether histopathologically typical Spitz nevi occurring in patients 50 years and older show any abnormalities regarding the 9p21 CDKN2A tumor suppressor gene locus. p16 immunohistochemistry (IHC), as well as dual-color FISH for assessment of diploid or hypodiploid status at 9p21, was performed in 25 classic Spitz nevi from patients 50 years and older and was compared with findings in a younger control population. All cases of typical Spitz nevi occurring in older patients retained p16 expression by immunohistochemistry and showed normal, diploid 9p21 FISH signals. Heterozygous loss of 9p21 by FISH was noted in a control case of a 9-year-old girl and is of unknown significance. These findings indicate that p16 expression by immunohistochemistry in classic Spitz nevi correlates well with absence of malignancy-associated cytogenetic abnormalities at 9p21 by FISH independent of the patient's age. Assessment of p16 expression by standard immunohistochemistry may therefore be reassuring in routine clinical practice when the patient is of advanced age, and can be helpful as a screening tool to select IHC-negative cases for extended FISH analysis targeting the 9p21 gene locus.

Intratumoral heterogeneity of chromosome 9 loss and CDKN2A (p16) protein expression in a morphologically challenging spitzoid melanoma

In young adults and children, spitzoid melanoma carries striking resemblance to spitz nevus clinically and histopathologically. Many have attempted to differentiate between these 2 entities by searching for immunohistochemical and molecular diagnostic differences. Here, the authors report a spitzoid melanoma in a young adult, which was morphologically similar to a spitzoid nevus and carried a loss of chromosome 9 detected by an array-based comparative genomic hybridization. However, the expression of cyclin-dependent kinase inhibitor 2A (p16) protein, encoded on chromosome 9p21, detected by the immunohistochemical study was heterogeneous among tumor cells. This case demonstrates the presence of clonal heterogeneity of losses of chromosome 9 and p16 protein expression within a single spitzoid melanoma, challenging a robust application of p16 expression detected only by immunohistochemical staining in determining the diagnosis of spitzoid melanoma.

Sentinel lymph node metastasis is not predictive of poor outcome in patients with problematic spitzoid melanocytic tumors

The diagnosis and clinical management of spitzoid melanocytic tumors with atypical features remain problematic and controversial. In the past decade, sentinel lymph node mapping has been advocated as a diagnostic test in this setting to discriminate melanoma from benign tumors. Recent studies, however, consistently show that despite the presence of lymph node metastases these patients almost always fare well. We investigated the outcome of patients with atypical Spitz tumors and spitzoid melanoma who received sentinel lymph node mapping to clarify current recommendations in managing patients with these diagnostically challenging tumors. A search of the electronic files of the Massachusetts General Hospital Pathology Service identified 41 patients treated with sentinel lymph node biopsy for atypical Spitz tumor or spitzoid melanoma from 1998 to 2008. These patients included 23 patients with atypical Spitz tumors and 17 patients with spitzoid melanoma. Sentinel lymph nodes were positive in 26% of patients with atypical Spitz tumors (6/23) and 35% with spitzoid melanomas (6/17). One patient with spitzoid melanoma developed in-transit metastasis; 0 of 40 patients developed metastases beyond the regional lymph node basin with a mean follow-up of 57 months. Sentinel lymph node biopsy may not be a reliable prognostic discriminatory test in patients with atypical Spitz tumors. Patients with spitzoid melanomas and positive sentinel lymph nodes have a more indolent course than those with bona fide conventional melanoma and positive sentinel nodes.