Reawakening to the existence of juvenile xanthogranuloma

NTRK expression is common in xanthogranuloma and is associated with the solitary variant

BACKGROUND

Previously identified mutually-exclusive driver genes in juvenile xanthogranuloma (JXG) and adult xanthogranuloma (AXG) include mutations in MAP kinase pathway genes such as MAP2K1, BRAF, ARAF, KRAS, NRAS, PIK3CD as well as fusions in BRAF and ALK, with a subset of cases with no identified driver yet. NTRK fusion has been identified in rare cases.

METHODS

We identified two consecutive index cases of localized JXG or AXG with NTRK1 fusion by next-generation sequencing (NGS) and confirmed by pan-NTRK immunostain. We expanded the study to a total of 50 cases of JXG and AXG using screening by pan-NTRK immunostain. We confirmed the specificity of our approach with negative results in 5 cases of histiocytic neoplasia lacking an NTRK fusion by NGS and 14 cases of non-neoplastic histiocytic disease.

RESULTS

We found 23 cases of JXG or AXG with overexpression of NTRK by immunostain, and these cases were restricted to localized disease (23 of 43 cases, 53.5%) rather than disseminated disease (zero of seven cases).

CONCLUSIONS

NTRK expression is common in JXG or AXG and associated with localized rather than disseminated disease. We speculate that the potential importance of this in JXG and AXG has not been previously appreciated due to the tendency to focus sequencing studies on disseminated disease. We confirm the presence of an NTRK1 fusion in two positive cases by NGS, however, additional genetic studies are necessary to further explore this.

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.

Contributions of Dr. Louis "Pepper" Dehner to the art of cutaneous pathology, the first pediatric dermatopathologist

Dr. Louis "Pepper" Dehner has been one of the most influential surgical pathologists of the last century. Authoring more than 450 publications, he is the premier modern pediatric pathologist. Perhaps, an area that he is less recognized and in which we would like to describe his contributions, is his role as a creator of the art of pediatric dermatopathology. Dr. Dehner has had at least 50 major publications describing, discovering, and orienting the discipline in the fields of fibrohistiocytic disorders of childhood, vascular tumors, and histiocytosis among many others. Dr. Dehner has clearly manifested that while many similarities between adult and pediatric surgical pathology exist, "children get different diseases." It is because of his mindful analysis and translation of the clinico-pathologic and biologic correlative between specific entities and advances in the field he has made that we are honored to describe some of his contributions to this particular area.

Juvenile xanthogranuloma: an unusual cause of intratesticular mass in childhood

Juvenile xanthogranuloma (JXG) is a common histiocytic disorder of infancy and early childhood, most frequently presenting with cutaneous lesions. Whereas involvement of several visceral sites is well documented, only 4 cases of primary testicular JXG have been reported. Although this benign disorder typically presents with a favorable clinical outcome, the unusual presentation as an intratesticular lesion can lead to diagnostic challenges. In this study, we present the case of a 6-month-old male child with an incidentally discovered testicular mass that was diagnosed as a JXG and briefly review the existing literature in an attempt to bring awareness to this uncommon presentation.

Neonatal systemic juvenile xanthogranuloma with an ominous presentation and successful treatment

This case report originated from a case of neonatal multisystemic juvenile xanthogranuloma (JXG). The patient presented with blue muffin rush, cervical mass, bone destruction, lung nodule, hepatosplenomegaly, and coagulopathy and was successfully treated with Langerhans cell histiocytosis (LCH) based chemotherapy treatment. Similar cases in literature were reviewed and it seems that JXG, a relatively benign entity, when presented in its systemic form with liver involvement, could have an aggressive course and portend quite poor prognosis. Challenges and special consideration of the diagnosis, treatment, and future case observation are discussed.