Lymphomatoid Papulosis in Children and Adolescents: A Systematic Review

Paediatric-onset lymphomatoid papulosis: results of a multicentre retrospective cohort study on behalf of the EORTC Cutaneous Lymphoma Tumours Group (CLTG)

BACKGROUND

Lymphomatoid papulosis (LyP) is a rare cutaneous T-cell lymphoproliferative disorder. Comprehensive data on LyP in the paediatric population are scarce.

OBJECTIVES

To characterize the epidemiological, clinical, histopathological and prognostic features of paediatric LyP.

METHODS

This was a retrospective multicentre international cohort study that included 87 children and adolescents with LyP diagnosed between 1998 and 2022. Patients aged ≤ 18 years at disease onset were included. LyP diagnosis was made in each centre, based on clinicopathological correlation.

RESULTS

Eighty-seven patients from 12 centres were included. Mean age at disease onset was 7.0 years (range 3 months-18 years) with a male to female ratio of 2 : 1. Mean time between the onset of the first cutaneous lesions and diagnosis was 1.3 years (range 0-14). Initial misdiagnosis concerned 26% of patients. LyP was most often misdiagnosed as pityriasis lichenoides et varioliformis acuta, insect bites or mollusca contagiosa. Erythematous papules or papulonodules were the most frequent clinical presentation. Pruritus was specifically mentioned in 21% of patients. The main histological subtype was type A in 55% of cases. When analysed, monoclonal T-cell receptor rearrangement was found in 77% of skin biopsies. The overall survival rate was 100%, with follow-up at 5 years available for 33 patients and at 15 years for 8 patients. Associated haematological malignancy (HM) occurred in 10% of cases (n = 7/73), including four patients with mycosis fungoides, one with primary cutaneous anaplastic large cell lymphoma (ALCL), one with systemic ALCL and one with acute myeloid leukaemia. If we compared incidence rates of cancer with the world population aged 0-19 years from 2001 to 2010, we estimated a significantly higher risk of associated malignancy in general, occurring before the age of 19 years (incidence rate ratio 87.49, 95% confidence interval 86.01-88.99).

CONCLUSIONS

We report epidemiological data from a large international cohort of children and adolescents with LyP. Overall, the disease prognosis is good, with excellent survival rates for all patients. Owing to an increased risk of associated HM, long-term follow-up should be recommended for patients with LyP.

Paediatric cutaneous lymphomas including rare subtypes: A 40-year experience at a tertiary referral centre

BACKGROUND

Primary cutaneous lymphomas are neoplasms of the immune system with a distinct tropism for the skin and an absence of extracutaneous manifestations at the time of diagnosis. Studies focusing on cutaneous lymphomas in children and adolescents remain scarce and often do not encompass the rare subtypes.

OBJECTIVES

To address this knowledge gap by describing the clinical, histological and molecular characteristics of a large group of paediatric patients affected by primary cutaneous lymphoma. We also provided the Paediatric Primary Cutaneous Lymphoma Atlas that illustrates the clinicopathological spectrum of observed presentations, in the hope of supporting other physicians in the diagnostic process.

METHODS

Retrospective chart review of paediatric patients diagnosed with primary cutaneous lymphomas between 1980 and 2022 at the Paediatric Dermatology Unit of Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan.

RESULTS

A total of 101 patients (58 males, 43 females) met the inclusion criteria. The most common subtypes were lymphomatoid papulosis (n = 48) and mycosis fungoides (n = 31). These were followed by primary cutaneous CD4+ small/medium T-cell lymphoproliferative disorders (n = 7), primary cutaneous anaplastic large-cell lymphomas (n = 5), primary cutaneous marginal zone B-cell lymphomas (n = 3), primary cutaneous follicle centre lymphomas (n = 2), subcutaneous panniculitis-like T-cell lymphomas (n = 2), primary cutaneous peripheral T-cell lymphoma not otherwise specified (n = 1), primary cutaneous precursor B-lymphoblastic lymphoma (n = 1) and Sézary syndrome (n = 1). Clinical follow-up data covering a median of 70.8 months (range 1-324) were available for 74 patients, of whom three died due to cutaneous lymphoma.

CONCLUSIONS

Our findings shed light on the peculiar aspects and long-term outcomes of paediatric cutaneous lymphomas, particularly emphasizing their distinctive features in comparison to their adult counterparts and exploring the less common subtypes. Further larger-scale studies are warranted to better characterize these entities and to achieve a more rapid and accurate diagnosis.

Diagnosis and management of cutaneous lymphomas and lymphoid proliferations in children, adolescents and young adults (CAYA)

Cutaneous lymphomas and lymphoid proliferations (LPD) in children, adolescents, and young adults (CAYA) are a heterogeneous group of lymphoid neoplasms that present formidable diagnostic challenges to clinicians and pathologists alike. Although rare overall, cutaneous lymphomas/LPD occur in real-world settings and awareness of the differential diagnosis, potential complications, and various therapeutic approaches will help ensure the optimal diagnostic work-up and clinical management. Lymphomas/LPD involving the skin can occur as primary cutaneous disease in a patient that characteristically has lymphoma/LPD confined to the skin, or as secondary involvement in patients with systemic disease. This review will comprehensively summarize both primary cutaneous lymphomas/LPD that occur in the CAYA population as well as those CAYA systemic lymphomas/LPD with propensity for secondary cutaneous involvement. Focus on the most common primary entities occurring in CAYA will include lymphomatoid papulosis, primary cutaneous anaplastic large cell lymphoma, mycosis fungoides, subcutaneous panniculitis-like T-cell lymphoma, and hydroa vacciniforme lymphoproliferative disorder.

Etiopathogenesis, Diagnosis, and Treatment Strategies for Lymphomatoid Papulosis with Particular Emphasis on the Role of the Immune System

Lymphomatoid papulosis (LyP) is a very rare disease that belongs to the group of CD30+ lymphoproliferative skin diseases. LyP is localized or generalized and usually presents as isolated or clustered red/brown-red lesions in the form of nodules and/or papules. The course of the disease is in most cases mild; however, depending on concomitant risk factors and history, it may progress to lymphoma, significantly reducing the survival rate and prognosis. Importantly, the clinical picture of the disease remains somewhat ambiguous, leading to a large number of misdiagnoses that result in inappropriate treatment, which is usually insufficient to alleviate symptoms. In addition to clinical manifestations, the histological characteristics vary widely and usually overlap with other conditions, especially those belonging to the group of lymphoproliferative disorders. Although diagnosis remains a challenge, several recommendations and guidelines have been introduced to standardize and facilitate the diagnostic process. This article reviews the available literature on the most important aspects of etiopathogenesis, clinical and histopathological features, diagnostic criteria, and possible treatment strategies for LyP, with particular emphasis on the role of the immune system.

Two Histologic Patterns of Lymphomatoid Papulosis Occurring in a Child: A Matter of Timing?

There are several histologic patterns seen in lymphomatoid papulosis, with the possibility of different subtypes occurring in the same patient. We report a case of lymphomatoid papulosis presenting with 2 histologic subtypes (types A and B) occurring concomitantly in a 10-year-old child, and postulate that the different subtypes occur dependent on the age of the lesion biopsied. Incidentally, one of the biopsies also shows a rarely seen pattern of pseudoepitheliomatous hyperplasia in a pediatric lymphomatoid papulosis patient.

Pediatric Cutaneous Hematologic Disorders: Cutaneous Lymphoma and Leukemia Cutis: Experience of a Tertiary-Care Pediatric Institution and Review of the Literature

BACKGROUND

Cutaneous hematologic malignancies are rare in children, and the literature about them is still sparse.

OBJECTIVE

The purpose of our study was to report our experience with pediatric cases of cutaneous hematologic disorders and describe their clinical and histological features.

METHODS

Data were retrospectively collected from the histopathologic database of the CHU Sainte-Justine, University of Montreal, Montreal, Canada. All patients up to 18 years of age with a diagnosis of a primary cutaneous lymphoma (including lymphomatoid papulosis), secondary cutaneous lymphoma or cutaneous manifestations of leukemia, followed from 1980 to 2019 at our center were reviewed.

RESULTS

Thirty-six patients were included. Age at presentation ranged from birth to 18 years of age (mean 7.83 ± 5.16; median 7.0). Ten different hematologic disorders were identified according to the WHO-EORTC classifications: lymphomatoid papulosis (10 cases), mycosis fungoides (6 cases), anaplastic large cell lymphoma (4 cases), pre-B acute lymphoid leukemia (5 cases), primary cutaneous marginal zone B-cell lymphoma (4 cases), primary cutaneous CD4⁺medium T-cell lymphoproliferative disorder (1 case), extranodal NK/T-cell lymphoma (1 case), hydroa vacciniforme-like lymphoproliferative disorder (1 case), B-cell lymphoblastic lymphoma (1 case) and acute myeloid leukemia (3 cases).

CONCLUSION

The most common subtype of cutaneous hematologic disease in our single institution study was lymphomatoid papulosis (type A and type C), followed by mycosis fungoides. Recognition of this large clinical and histological spectrum by dermatologists is important because diagnosis is often established by biopsy of skin lesions, even in secondary cutaneous cases. Moreover, the clinicopathological correlation is of utmost importance for the final diagnosis of those pathologies.

Lymphomatoid Papulosis Development in Acute Lymphoblastic Leukemia

Lymphomatoid papulosis (LyP) is a chronic, recurrent benign skin disease characterized by histological features of a CD 30-positive cutaneous T-cell lymphoproliferative disorder. It is rare, with an annual, worldwide incidence of 1.2 - 1.9 per million, and accounts for 16-47% of pediatric cutaneous lymphoproliferative disorders. It often occurs on the extremities or the trunk and rarely affects the face or genitals. Its onset may be triggered by irradiation therapy, immunomodulating agents, infection or atopic dermatitis. It has a benign course but is associated with certain hematological malignancies. Mycosis fungoides and primary cutaneous anaplastic large cell lymphoma are the most commonly associated hematological malignancies. The incidence of lymphoma in children with LyP has been reported to be 8.5% at most. Most patients who develop lymphomas do so within 4 years of the LyP onset; therefore, patients with LyP should be carefully followed up. Herein, we report a case in which tumors appeared in the left scrotum and under the left lip during maintenance therapy for precursor B-cell acute lymphoblastic leukemia. We needed to distinguish the tumor from extramedullary recurrence of ALL or de novo other cutaneous lymphoma; however, the histological findings of a tumor biopsy resulted in a diagnosis of LyP.

Primary cutaneous T-cell lymphomas in childhood and adolescence

Primary cutaneous lymphomas are extranodal non-Hodgkin lymphomas of T- or B- cell origin, that predominantly affect older patients but have been reported in all age groups and as early as in the first years of life. Diagnosis of cutaneous lymphomas is challenging and requires high clinical suspicion and close collaboration between dermatologists, pediatric oncologists and pathologists. Skin involvement of non-Hodgkin lymphomas in children or adolescents can either be primary cutaneous or secondary due to an underlying nodal lymphoma. The most common primary cutaneous lymphomas encountered in children are of T-cell origin, with mycosis fungoides being the most prevalent cutaneous T-cell lymphoma, followed by CD30⁺ lymphoproliferative disorders. While cutaneous lymphomas share clinicopathologic characteristics between juvenile and adult forms, there are important differences in terms of clinical presentation, diagnosis and treatment. The hypopigmented variant of mycosis fungoides seems to be overrepresented in the pediatric age group. Prognosis and treatment of mycosis fungoides are stage dependent. The majority of children present with early-stage disease and respond well to topical corticosteroids and phototherapy.

Primary cutaneous T-cell lymphomas other than Mycosis Fungoides and Sezary Syndrome - Part I: Clinical and histologic features and diagnosis

Primary cutaneous T-cell lymphomas (CTCLs) are defined as lymphomas with a T-cell phenotype that present in the skin without evidence of systemic or extracutaneous disease at initial presentation. CTCLs other than Mycosis Fungoides (MF) and Sézary syndrome (SS) account for approximately one-third of CTCLs and encompass a heterogenous group of non-Hodgkin lymphomas ranging from indolent lymphoproliferative disorders to aggressive malignancies with a poor prognosis. The spectrum of CTCLs continues to broaden as new provisional entities are classified. Given the morphologic and histologic overlap among CTCLs and other diagnoses, a thorough clinical history, physical evaluation, and clinicopathologic correlation are essential in the workup and diagnosis of these rare entities. This article will summarize the epidemiologic, clinical, pathologic, and diagnostic features of CTCLs other than MF and SS.

Primär kutane T‐Zell‐Lymphome im Kindes‐ und Jugendalter

Primär kutane Lymphome sind extranodale T- oder B-Zell-Non-Hodgkin-Lymphome, die vorwiegend ältere Patienten betreffen, aber in allen Altersgruppen einschließlich der ersten Lebensjahre auftreten können. Die Diagnose kutaner Lymphome ist eine Herausforderung und erfordert einen hohen klinischen Verdacht sowie enge Zusammenarbeit zwischen Dermatologen, pädiatrischen Onkologen und Pathologen. Generell müssen primär kutane Lymphome von sekundär kutanen Lymphomen, welche meist von nodalen oder extranodalen Lymphomen ausgehen, unterschieden werden. Die häufigsten primär kutanen Lymphome im Kindesalter sind T-Zell Lymphome, wobei Mycosis fungoides das häufigste kutane T-Zell-Lymphom darstellt, gefolgt von CD30+ lymphoproliferativen Erkrankungen. Während klinisch-pathologische Merkmale kutaner Lymphome bei Jugendlichen und Erwachsenen ähnlich sind, gibt es wichtige Unterschiede bezüglich klinischer Präsentation, Diagnose und Behandlung. Die hypopigmentierte Variante der Mycosis fungoides scheint in der pädiatrischen Altersgruppe überrepräsentiert zu sein. Prognose und Behandlung der Mycosis fungoides sind stadienabhängig. Die Mehrheit der Kinder weist ein frühes Krankheitsstadium auf und spricht gut auf topische Kortikosteroide und Phototherapie an.

A case of lymphomatoid papulosis type E in a young adult: An uncommon entity

Lymphomatoid papulosis (LyP) type E is a rare variant of the primary cutaneous CD30+ lymphoproliferative disorders, characterized clinically by large necrotic eschar-like lesions and histopathologically by angiodestructive and angioinvasive infiltrates of CD30+ lymphocytes. As in other forms of lymphomatoid papulosis, type E lesions may undergo spontaneous regression after weeks, with frequent recurrences. We report a 21-year old male with an angiodestructive infiltrate of CD30+ lymphocytes manifesting as a papular eruption rather than ulceration, and suggest that this clinical phenotype might be related to the presence of CD4+ lymphocytes in the inflammatory cell infiltrate.

Evaluation of Associated Lymphomas and Their Risk Factors in Patients with Lymphomatoid Papulosis: A Retrospective Single-Center Study from Turkey

Objective:

Lymphomatoid papulosis (LyP) is an indolent skin disease with variable clinical features classified among the primary cutaneous CD30+ T-cell lymphoproliferative disorders. It may show association with cutaneous and systemic lymphomas. We aimed to identify the frequency and characteristics of associated lymphomas among Turkish patients with LyP and to determine the risk factors for secondary lymphomas.

Materials and Methods:

The files of patients diagnosed with LyP between 1998 and 2018 in a tertiary dermatology clinic were retrospectively analyzed. Univariate and multivariate models were used to assess the possible risk factors for secondary lymphomas, such as demographic and clinical characteristics of the patients.

Results:

Among 61 patients (47 adults, 14 children) with LyP, a total of 22 secondary lymphomas were observed in 20 patients. Nineteen of them were adults. Mycosis fungoides (MF) was the major associated lymphoma (n=19) followed by systemic anaplastic large cell lymphoma (ALCL) (n=2) and primary cutaneous ALCL (n=1). The most common stage in patients with accompanying MF was stage IB (n=11). While 18 patients showed the classical type of MF, one patient had folliculotropic MF. When the risk factors for association between LyP and other lymphomas were evaluated, only older age was found to be a significant risk factor and existence of ulcerated lesions was found to be a negative indicator.

Conclusion:

LyP is not rare in the pediatric population. MF is the most common associated lymphoma in patients with LyP. Adult LyP patients are more commonly associated with secondary lymphomas than pediatric patients. Older age at the time of diagnosis of LyP is a significant risk factor for associated lymphomas.

A case of pediatric lymphomatoid papulosis treated with photodynamic therapy and narrowband ultraviolet B

We report a case of a 13-year-old boy with extensive lymphomatoid papulosis (LyP) involving his elbows, forearms, proximal thighs, and right hip, with treatment-resistant nodules on his right forearm. He was treated with full-body narrowband ultraviolet B and targeted photodynamic therapy (PDT) with 20% aminolevulinic acid (ALA). After two months, there was complete resolution of the right forearm nodules. Due to its minimal toxicity, PDT offers unique advantages and may be considered for pediatric LyP patients with symptomatic, localized disease resistant to conventional treatments.

Breast Implant-Associated Anaplastic Large-Cell Lymphoma: Current Understanding and Recommendations for Management

Worldwide, millions of women live with breast implants. Therefore, it is important that physicians be aware of an uncommon but possibly serious complication arising from breast implants: breast implant-associated anaplastic large cell lymphoma (BIA-ALCL). Breast implant-associated anaplastic large-cell lymphoma most commonly presents as a delayed fluid collection around a textured breast implant or as a mass in the capsule surrounding the implant. The exact pathogenesis of the disease remains unclear. The neoplastic cells of BIA-ALCL show strong uniform staining for CD30 and are consistently negative for activin receptor-like kinase 1. Patients with confirmed cases should be referred to a lymphoma specialist or breast medical oncologist for a complete oncologic evaluation before any surgical intervention. For disease confined to the fluid accumulation or capsule, or both, surgical removal of the implant and complete capsulectomy is the preferred treatment. Postoperative chemotherapy or radiation, or both, are not considered necessary for patients with limited-stage disease and are reserved for advanced disease stages. Generally, BIA-ALCL is a local disease that follows an indolent course and has an excellent prognosis. Although complete remission of disease has occurred in patients with BIA-ALCL, median overall survival is reduced. As of March 2018, approximately 529 unique, confirmed BIA-ALCL cases had been reported in 23 countries. To date, 16 patients have died from BIA-ALCL, and all had extracapsular involvement. The aim of this article is to summarize the diagnosis, evaluation, and management of BIA-ALCL, based on established guidelines, for all practitioners who may care for patients with breast implants.

A Systematic Approach to the Cutaneous Lymphoid Infiltrates: A Clinical, Morphologic, and Immunophenotypic Evaluation

CONTEXT.—

The evaluation of cutaneous lymphoid infiltrates, both neoplastic and inflammatory, occurs very frequently in routine dermatopathologic examination and consultation practices. The "tough" cutaneous lymphoid infiltrate is feared by many pathologists; skin biopsies are relatively small, whereas diagnostic possibilities are relatively broad. It is true that cutaneous lymphomas can be difficult to diagnose and that in many circumstances multiple biopsies are required to establish a correct diagnostic interpretation. As a reminder, one should understand that low-grade cutaneous lymphomas are indolent disorders that usually linger for decades and that therapy does not result in disease cure. It is also important to remember that in most circumstances, those patients will die from another process that is completely unrelated to a diagnosis of skin lymphoma (even in the absence of specific therapy).

OBJECTIVE.—

To use a clinicopathologic, immunophenotypic, and molecular approach in the evaluation of common lymphocytic infiltrates.

DATA SOURCES.—

An in-depth analysis of updated literature in the field of cutaneous lymphomas was done, with particular emphasis on updated terminology from the most recent World Health Organization classification of skin and hematologic tumors.

CONCLUSIONS.—

A diagnosis of cutaneous lymphoid infiltrates can be adequately approached using a systematic scheme following the proposed ABCDE system. Overall, cutaneous T- and B-cell lymphomas are rare and "reactive" infiltrates are more common. Evaluation of lymphoid proliferations should start with a good sense of knowledge of the clinical presentation of the lesions, the clinical differential considerations, and a conscientious and appropriate use of immunohistochemistry and molecular tools.

Lymphomatoid papulosis in children and adolescents: A clinical and histopathologic retrospective cohort

BACKGROUND, AIMS AND OBJECTIVES

Lymphomatoid papulosis (LyP) is a CD30+ lymphoproliferative disorder that is rare and not well described within the pediatric subpopulation. We sought to review the literature and characterize clinical and pathologic features among pediatric and adolescent patients diagnosed with LyP at a tertiary care center.

MATERIALS AND METHODS

A retrospective cohort of 27 pediatric and adolescent patients (defined as <20 years old) diagnosed with LyP at the Weill Cornell Medicine Dermatopathology division from 2006 to 2016 was identified. Subsequently, we reviewed the histopathologic characteristics and collected clinical follow-up data from patients and their providers. The parameters assessed included the pathological LyP subtype including the immunohistochemical staining pattern, the development of secondary lymphoma, disease duration and rate of remission.

RESULTS

While type A was the most prevalent subtype, B and C subtypes were also frequently observed. CD8 predominance was a common finding, especially among type B LyP patients and those with eccrinotropic granulomatous features. None of the patients with clinical follow-up have developed secondary lymphoma, and some patients experienced remission of their disease.

CONCLUSION

While type A appears to be the dominant variant described in children, types B, C, and even the newly described variants E and F may occur more often than previously reported. Pediatric LyP may be more indolent than the adult variant, but close clinical follow-up is still warranted.

How I treat primary cutaneous CD30+ lymphoproliferative disorders

The primary cutaneous CD30+ lymphoproliferative disorders are a family of extranodal lymphoid neoplasms that arise from mature postthymic T cells and localize to the skin. Current classification systems recognize lymphomatoid papulosis (LyP), primary cutaneous anaplastic large cell lymphoma, and borderline cases. In the majority of patients, the prognosis of primary cutaneous CD30+ lymphoproliferative disorders is excellent; however, relapses are common, and complete cures are rare. Skin-directed and systemic therapies are used as monotherapy or in combination to achieve the best disease control and minimize overall toxicity. We discuss 3 distinct presentations of primary cutaneous CD30+ lymphoproliferative disorder and present recommendations for a multidisciplinary team approach to diagnosis, evaluation, and management of these conditions in keeping with existing consensus guidelines.

CD30-Positive Lymphoproliferative Disorders

Primary cutaneous CD30-positive lymphoproliferative disorders (CD30+ LPD) encompass lymphomatoid papulosis (LyP), primary cutaneous anaplastic large cell lymphoma (pcALCL), and borderline lesions [1]. CD30+ LPD are the second most common cutaneous T-cell lymphomas (CTCL) after mycosis fungoides (MF) and represent approximately 25% of all CTCL cases [2]. Their common phenotypic hallmark is an expression of the CD30 antigen, a cytokine receptor belonging to the tumor necrosis factor (TNF) receptor superfamily. Both LyP and pcALCL show numerous clinical, histological and immunophenotypic variants, and generally have an indolent course with a favorable prognosis. Overlapping features of LyP and pcALCL with other CD30+ T-cell lymphomas, inflammatory, and/or infectious conditions emphasize the importance of careful clinicopathologic correlation and staging.

How to Diagnose and Treat Breast Implant-Associated Anaplastic Large Cell Lymphoma

LEARNING OBJECTIVES

After reading this article, the participant should be able to: 1. Describe the diagnostic criteria for breast implant-associated (BIA) anaplastic large cell lymphoma (ALCL). 2. Appropriately evaluate a patient with suspected BIA-ALCL, including appropriate imaging, laboratory tests, and pathologic evaluation. 3. Understand the operative treatment of BIA-ALCL, and indications for systemic chemotherapy and/or radiation therapy in advanced disease. 4. Understand treatment outcomes and prognosis based on stage of disease.

SUMMARY

The goal of this continuing medical education module is to present the assessment of a patient with suspected breast implant-associated anaplastic large cell lymphoma, the evaluation and diagnosis, the preoperative oncologic workup, the formation and execution of a surgical treatment plan, and the inclusion of adjunct treatments when indicated. In addition, staging and disease progression for treatment of breast implant-associated anaplastic large cell lymphoma are discussed.

Cutaneous Hematolymphoid and Histiocytic Proliferations in Children

This article focuses on cutaneous hematopoietic neoplasms that are more likely to be encountered in the pediatric age-group and includes both lymphoproliferative and histiocytic disorders. The cutaneous hematologic disorders in children have a different epidemiologic profile to what is seen during adulthood. Although mycosis fungoides is the most frequent form of cutaneous lymphoma in adults, it is very rare in children. Because lymphoblastic leukemias and lymphomas are more frequent in the pediatric setting, cutaneous leukemic infiltrates are relatively common in this age-group. Similarly, histiocytic disorders are more common in children, particularly Langerhans cell histiocytosis and juvenile xanthogranuloma. Notably, the histiocytic disorders have undergone significant modifications on their nomenclature in the basis of the molecular characteristics that are present in them. A summary of the most frequent cutaneous hematopoietic disorders in children will be discussed further in this review.