Langerhans Cell Histiocytoma: A Benign Histiocytic Neoplasm of Diverse Lines of Terminal Differentiation

BRAF Mutation Analysis in Two Cases of Congenital Self-Healing Langerhans Cell Histiocytosis

Congenital self-healing Langerhans cell histiocytosis (CSHLCH) is a rare type of Langerhans cell histiocytosis (LCH). Here, we report two cases of CSHLCH. The cases presented solitary and multiple skin lesions of various sizes. The diagnosis was confirmed by skin biopsies. The lesions disappeared after one to two months without therapeutic intervention. No BRAF mutations in the skin lesions were detected, and soluble interleukin-2 receptor (sIL-2R) was normal in both cases. Recent studies suggested that the state of differentiation of the precursor cell in which BRAF mutations occur is associated with the clinical types and prognosis of the disease. Further investigation should be needed to elucidate the association between the progression and regression of CSHLCH and BRAF mutation.

What to Look Out for in a Newborn with Multiple Papulonodular Skin Lesions at Birth

Multiple papulonodular skin lesions at birth can indicate the presence of various benign and malignant disorders. Although the lesions’ clinical aspect (color and consistency, in particular) may steer the clinician towards one disorder or another (infantile myofibromatosis, xanthogranuloma, or metastatic neuroblastoma), the diagnosis can only be confirmed by the histopathologic assessment of a biopsy. In neonates, a rapid but accurate diagnosis is critical because skin lesions may be the first manifestation of a malignant disorder like leukemia cutis or metastatic neuroblastoma. Here, we review the various disorders that may manifest themselves as multiple skin lesions at birth.

Histiocytosis

Histiocytoses constitute a heterogeneous group of rare disorders, characterised by infiltration of almost any organ by myeloid cells with diverse macrophage or dendritic cell phenotypes. Histiocytoses can start at any age. Diagnosis is based on histology in combination with appropriate clinical and radiological findings. The low incidence and broad spectrum of clinical manifestations often leads to diagnostic delay, especially for adults. In most cases, biopsy specimens infiltrated by histiocytes have somatic mutations in genes activating the MAP kinase cell-signalling pathway. These mutations might also be present in blood cells and haematopoietic progenitors of patients with multisystem disease. A comprehensive range of investigations and molecular typing are essential to accurately predict prognosis, which can vary from spontaneous resolution to life-threatening disseminated disease. Targeted therapies with BRAF or MEK inhibitors have revolutionised salvage treatment. However, the type and duration of treatment are still debated, and the prevention of neurological sequelae remains a crucial issue.

Congenital Unilesional Cutaneous Langerhans Cell Histiocytosis: A Case Report

ABSTRACT

Langerhans cell histiocytosis (LCH) is a clonal proliferation of bone-marrow-derived cells, which normally reside as epidermal and mucosal dendritic cells involved in antigen presentation. It is a rare disease more common in children than adults, that is believed to be neoplastic in most cases. The diagnosis is based on clinical and radiological findings in combination with histopathologic, immunophenotypic, or ultrastructural analyses. LCH have a broad spectrum of clinical manifestations, ranging from benign cutaneous lesions to malignant multisystem disease. Based on the extent of involvement at diagnosis, LCH can be divided in single-system LCH when only one organ or system is involved, usually with multiple lesions, and multisystem LCH, when 2 or more organs or systems are involved at diagnosis. One variant of LCH is characterized by congenital isolated cutaneous involvement. It typically manifests at birth or in the postnatal period with a widespread eruption of red-to-brown papulo-nodules or, more uncommonly, a solitary lesion. The overall prognosis for single lesion skin limited LCH is excellent and most lesions spontaneously resolve within 4-18 weeks. Systemic involvement is rare. Skin findings cannot predict systemic disease and obtaining an oncology consultation is recommended for further evaluation. Herein, we present an additional case in a full-term, well-appearing, female infant with an isolated, asymptomatic, ulcerated, papule of the left arm, that was noted at birth.