Cutaneous lesions of Letterer-Siwe disease. Electron microscopic study

BRAF V600E-Positive Multisite Langerhans Cell Histiocytosis in a Preterm Neonate

Hemorrhagic pustules with a "blueberry muffin" appearance accompanied by respiratory failure in a neonate present a challenging differential diagnosis that includes infections and neoplasms. We present a case of multiorgan, multisite Langerhans cell histiocytosis (LCH), positive for the oncogenic BRAF V600E mutation, in a preterm neonate. Infants with LCH pose a diagnostic challenge due to their heterogeneous presentations. This case is unusual in that the newborn presented with severe multiorgan involvement. Due to the rare incidence, wide spectrum of clinical manifestations, and high mortality rate, clinicians must maintain a high index of suspicion for LCH.

Pathogenesis of Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) combines in one nosological category a group of diseases that have widely disparate clinical manifestations but are all characterized by accumulation of proliferating cells with surface markers and ultrastructural features similar to cutaneous Langerhans cells (LCs). Despite this unified nosology, important questions about LCH remain unanswered. First, despite having phenotypic features of LCs, LCH cell gene-expression patterns differ from those in LCs. Although this observation suggests that LCH may arise from an earlier precursor, it is not necessarily inconsistent with the hypothesis that LCs are the cell of origin for LCH. Second, LCH's prominent inflammatory component and occasional benign clinical course suggest that LCH may not be a neoplasm. However, the demonstration that LCH cells are clonal, along with the recent discovery of activating BRAF mutations in LCH cells, strongly suggests that LCH is a neoplastic disease. These new observations point the way to rationally targeted therapies.

Recent advances in the understanding of Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is a proliferative disease of cells that share phenotypic characteristics with the primary antigen presenting cells of the epidermis. Its clinical manifestations are highly variable, extending from very benign forms to a disseminated, aggressive disease that causes significant mortality. Although many of the fundamental pathogenetic features of LCH have been enigmatic, recent advances have led to a much clearer understanding of the disease. In particular, careful molecular analyses of mouse models and human LCH samples suggest that LCH's cell of origin may not be the epidermal LC itself but a myeloid-derived precursor. Advanced genomic technologies have revealed the presence of activating, somatic BRAF mutations in the majority of patient specimens. Together, these observations have produced a new picture of LCH as a myeloid neoplasm. These advances are likely to have profound implications for the use of targeted therapeutics in LCH.

Langerhans cell histiocytosis research. Past, present, and future

This article reviews the various investigative events that led to the endorsement of the term Langerhans cell histiocytosis for the various clinicopathologic conditions previously called Hand-Schüller-Christian disease, Abt-Letterer-Siwe disease, eosinophilic granuloma of bone, and histiocytosis X. The different denominations reflect the changing conceptual approaches to the so-called reticuloendothelial system and the successive acquisition of new ultrastructural and immunocytochemical data.

Langerhans cell histiocytosis masquerading as lichen aureus

We report a 13-year-old boy with localized Langerhans cell histiocytosis. The lesion was restricted to the skin of the mons pubis and clinically resembled lichen aureus. Histopathologic and electron microscopic examinations of a skin biopsy specimen of the lesion showed typical features of Langerhans cell histiocytosis. Extensive examination revealed no other organ involvement.

Epidermotropic primary neuroendocrine (Merkel cell) carcinoma of the skin with Pautrier-like microabscesses. Report of three cases and review of the literature

Three cases of primary cutaneous neuroendocrine carcinoma involving the face are reported. In the first patient the tumor developed in the scar of a previously excised basal cell carcinoma of the nose, recurred locally, and metastasized to a regional lymph node 2 1/2 years after initial treatment. In the second and third patients the tumors were located on the forehead and were removed with a wide excision. In the second patient the tumor metastasized to regional lymph nodes 1 month after treatment. Light microscopic examination in all patients showed an undifferentiated, small cell, dermal tumor with prominent epidermotropism, forming Pautrier-like microabscesses. Immunohistochemical staining for neuron-specific enolase was positive, and ultrastructural examination revealed numerous cytoplasmic neurosecretory granules and paranuclear aggregates of intermediate-sized filaments. The literature concerning epidermal involvement by primary neuroendocrine carcinoma of the skin is reviewed; the relation with basal cell carcinoma and treatment are discussed.

Metastatic epidermotropic squamous cell carcinoma of the vagina

Epidermotropic carcinomas are neoplasms with an unusual but specific propensity for invading and intimately associating with the epidermis. A unique case of squamous cell carcinoma of the vagina with epidermotropic cutaneous metastases is described.

Coated Langerhans cell granules in histiocytosis X cells

Histiocytosis X cells (HXC) and epidermal Langerhans cells (LC) are thought to be closely related because they share morphologic features and immunologic markers. One of these common markers, the LC granule, is an acknowledged morphologic criterion for the identification of these cell types, but its function and, thus, significance are as yet unknown. In this study, we report the presence of a fuzzy coat radiating from the cytoplasmic face of the LC granule membrane in HXC. This bristly coat is indistinguishable from that of coated vesicles and pits and, thus, represents a strong morphologic clue to the function of LC granules because coated structures have been shown to be involved in the selective transport of molecules in eukaryotic cells.

Histiocytosis X cells in eosinophilic granuloma express Ia and T6 antigens

Morphologic similarities between histiocytosis X (HX) cells and epidermal Langerhans cells (LC) have led to the hypothesis that HX represents a proliferative disorder of LC. In order to prove the validity of this assumption, we tested single cell suspensions isolated from an eosinophilic granuloma type HX lesion for the presence of various antigenic determinants defined by monoclonal antibodies using an immunoelectron microscopic technique. An anti-Ia reagent reacted with essentially all histiocytic cells and a small portion of lymphocytes whereas plasma cells and eosinophils were negative. T6 antigen, in contrast, was disclosed exclusively on HX cells either with or without Birbeck granules. Pan-T cell-reagent OKT3 reacted only with small lymphocytes. The finding that HX cells from eosinophilic granuloma lesions are the only cells that have the identical surface marker equipment as epidermal LC (Ia antigens, T6 antigen, Fc-IgG, and C3 receptors) strongly supports the concept that these cells are derived from the LC lineage.

An ultrastructural and immunohistochemical study on mandibular lesion of Letterer-Siwe disease

A mandibular lesion from an infant with Letterer-Siwe disease was studied by electron microscopy and immunohistochemistry. Ultrastructurally, two types of cells were identified; clear and dark cells. Clear cells had indented nuclei and langerhans cell granules, while dark cells were characterized by the occasional presence of a large number of lysosomes. Lysozyme was usually not detectable in proliferating cells with indented nuclei, but it was strongly positive in cells without indented nuclei. The latter also usually contained IgG, although the occurrence of cytoplasmic IgM, A, D and E seemed to be negative in both types of cells. Thus clear cells showed a close resemblance to Langerhans cells and dark cells had features of ordinary histiocytes. Although the intimate relationship between these two types of cells remains obscure, our findings suggest that Letterer-Siwe disease may be a reactive or tumorous condition of a cellular subpopulation of Langerhans cells with a proliferation of differentiated histiocytes.

Histiocytosis X: current concepts and a report of two cases

The current concepts of histiocytosis X are discussed, and the literature concering this rare disease of obscure aetiology reviewed. Two case reports of histiocytosis X presenting in similar sites in young children of similar ages, but with markedly different courses, are presented. The importance of early recognition of the disease, particularly by the dental surgeon who may see the first oral signs, is stressed. Attention is drawn to the danger of misdiagnosing the oral signs of histiocytosis X, particularly as periodontal disease. The possible aetiologies are examined and current treatment regimes discussed.

Histiocytosis X. An analysis of 50 cases

Evidence is presented to support the author's view that Letter-Siwe disease, Hand-Schüller-Christian disease and eosinophilic granuloma are but variants of a single disease entity--histiocytosis X. The clinical behaviour of the disease and its prognosis are related to the age ofonset of the disease. Details of 50 cases of histiocytosis X have been analyzed. The mean age of presentation was 15 years 4 months. The male:female ratio was 3:2, 54% of patients in this series had disease confined to the jaws and oral cavity, males being more likely than females to have disseminated disease.

alpha-D-mannosidase activity in histiocytosis X

A histochemical study of enzymatic activities was undertaken in five cases of histiocytosis X (two localized bone forms, two generalized forms, and one involving mainly the skin), each of which revealed characteristic structural features at the optical and ultrastructural levels. A confirmation was made of the original assumption of high acid alpha-D-mannosidase activity, i.e. activity described in human Langerhans intraepidermal cells (Elleder, 1975). In the control group of tumors, with the exception of urticaria pigmentosa, enzyme activity was either at trace level or altogether absent. Acid alpha-D-mannosidase activity therefore appears to be the first biochemical feature common to both histiocytosis X and the Langerhans cells. The significance of the finding for the present theory of the histogenesis of the above tumors is discussed.

Atypical fibroxanthoma of the skin: an ultrastructural study of two cases

The ultrastructure of two atypical" fibroxanthomas of the skin was studied. The first lesion was a spindle cell tumor on light microscopy, which electron microscopy revealed was composed of undifferentiated mesenchymal cells. The second lesion had a highly pheomorphic appearance on both light and electron microscopy. It was formed by atypical histiocytic cells and abundant "typical" Langerhans cells. The second lesion was considered to be a proliferation either of atypical Langerhans cells or of histiocytes related to Langerhans cells. Thus, atypical fibroxanthoma of skin may not be a homogeneous entity but could be a group of mesenchymal proliferative lesion in a similar clinical setting.

A unique cytoplasmic structure in papular histiocytoma

Intracytoplasmic granules with a unique and highly complex ultrastructure, have been observed within the cellular infiltrate of the lesions of two patients with papular histiocytosis. Examination of serial sections has enabled construction of a three-dimensional model of these granules, which appear to be composed of an elaborate arrangement of membranes and vesicles. Two hypotheses (endocytosis and exocytosis) are proposed for the mode of formation of these unique cytoplasmic structures.

Systemic giant-cell histiocytosis: report of a case and a review of the adult form of Letterer-Siwe disease

The multiple classifications of histiocytic disorders, and the lack of specificity in their application, have degraded the utility of such diagnostic terms as "Letterer-Siwe Disease" and "Malignant Histiocytosis". A case is presented of a systemic histiocytic proliferation with erythrophagocytosis and giant-cell formation which does not fit into any presently accepted diagnostic niche. No similar case was found in the literature. Moreover, it appears that the entity "Adult form of Letterer-Siwe disease" has been uncritically accepted on the basis of a few poorly documented cases, and should be abandoned.

Ultrastructural changes induced by vinblastine in cutaneous lesions of histiocytosis X

The ultrastructural examination of the skin lesions of 2 typical patients with subacute disseminated histiocytosis X 12, 24, 36, 48 and 72 hours after the intravenous administration of vinblastine enabled us to observe that, after 12-24 hours, there were numerous Langerhans cells undergoing mitosis which had no spindle microtubules but showed fragments of newly forming nuclear membrane, thus demonstrating that mitosis was arrested in anaphase. Later on, in the Langerhans cells mainly, we observed degenerative phenomena (mitochondrial swelling, perinuclear edema and rupture of the plasma membrane) and, finally, a marked reduction in the number of this type of cells were observed.