Problems when diagnosing cutaneous leishmaniasis: a retrospective study analyzing clinical, histopathological and immunohistochemical features.

BACKGROUND: Cutaneous leishmaniasis (CL) incidence in Switzerland is rising due to factors like migration and globalization. The aim of this work was to investigate CL frequency in Switzerland and identify clinical and histopathological difficulties in diagnosing CL in a non-endemic country. PATIENTS AND METHODS: This retrospective study evaluated the clinical and histopathological characteristics of all CL cases from two dermatopathology laboratories between 2000 and 2022. Skin biopsies were histopathologically reviewed using HE, Giemsa, and immunohistochemical stain for CD1a and a specific Leishmania antibody (LA). PCR to detect Leishmania DNA was performed if sufficient tissue was available. RESULTS: 42 cases (27 m, 15 f) were included. The correct clinical diagnosis of CL was only made in 15 (35.7%) cases. In seven (16.6%) cases, CL was missed in the initial histopathologic evaluation. Two main histopathological patterns were observed: granulomatous and pseudolymphomatous. Immunohistochemical staining with CD1a and Leishmania-specific antibody was positive in 91% and 80% of cases, respectively. Leishmania PCR was positive in 25 of 26 cases, mainly detecting Old World species. CONCLUSIONS: CL is rare in Switzerland and often misdiagnosed clinically and histopathologically. CD1a and specific Leishmania antibody stainings are useful. CL should be considered in non-healing ulcers, even without a history of travel to endemic areas.

Pulmonary Langerhans Cell Histiocytosis: Diagnosis in Bronchoalveolar Lavage Liquid-Based Cytology Samples.

INTRODUCTION: Pulmonary Langerhans cell histiocytosis (PLCH) is a rare interstitial lung disease characterized by the accumulation of Langerhans cells within the lung tissue. The diagnosis of PLCH traditionally involves clinical, radiological, and lung biopsy histopathological evaluations. CASE PRESENTATION: We present 2 cases where the diagnosis of PLCH was confirmed through the analysis of bronchoalveolar lavage (BAL) fluid cytology using immunoperoxidase technique, highlighting the significance of this minimally invasive technique in the diagnostic process. Clinical and radiological examination suggested advanced interstitial lung disease characterized by a fibrocystic pattern in both cases. The cytologic analysis of the BAL fluid revealed typical histiocytes with longitudinal grooves and eosinophils, which was better seen on liquid-based cytology (LBC) smears. ICC with CD1a, Langerin, and S-100 confirmed the diagnosis of PLCH. CONCLUSION: Detecting PLCH through the examination of BAL cytology poses challenges, yet it is achievable, particularly with the assistance of LBC and ICC.

Anandamide modulation of monocyte-derived Langerhans cells: implications for immune homeostasis and skin inflammation.

Introduction: The endocannabinoid system (ECS), named after the chemical compounds found in the cannabis plant, is a regulatory network of neurotransmitters, receptors, and enzymes that plays crucial roles in skin health and disease. Endogenous ligands of the ECS, called endocannabinoids, have proven to be important regulators of immune responses. One of the most prevalent endocannabinoids, arachidonoylethanolamide (also known as anandamide), is known for its anti-inflammatory effects. Langerhans cells (LCs) are the sole antigen-presenting cells present in the human epidermis. They serve as the first line of defense against pathogens and are essential for the skin's specific immune responses and play a critical role in maintaining tissue homeostasis; however, little is known about the effect of endocannabinoids on these cells. Our research aimed to provide the connection between monocyte-derived Langerhans cells (moLCs) and the ECS, shedding light on their collaborative roles in immune homeostasis and inflammation. Methods: Human monocytes were differentiated into moLCs using established protocols. Anandamide was applied during the differentiation process to test its effect on the viability, marker expression, and cytokine production of the cells, as well as in short term treatments for intracellular calcium measurement. TLR ligands applied after the differentiation protocol were used to activate moLCs. The impact of anandamide on the functionality of moLCs was further assessed using differential gene expression analysis of bulk RNA-Seq data, moLC-T cell cocultures, while ELISpot was employed to determine polarization of T cells activated in the aforementioned cocultures. Results: Anandamide did not significantly affect the viability of moLCs up to 10 µM. When applied during the differentiation process it had only a negligible effect on CD207 expression, the prototypic marker of LCs; however, there was an observed reduction in CD1a expression by moLCs. Anandamide had no significant effects on the maturation status of moLCs, nor did it affect the maturation induced by TLR3 and TLR7/8 agonists. MoLCs differentiated in the presence of anandamide did however show decreased production of CXCL8, IL-6, IL-10 and IL-12 cytokines induced by TLR3 and TLR7/8 activation. Anandamide-treated moLCs showed an increased capability to activate naïve T cells; however, not to the level seen with combined TLR agonism. RNA sequencing analysis of moLCs differentiated with anandamide showed modest changes compared to control cells but did reveal an inhibitory effect on oxidative phosphorylation specifically in activated moLCs. Anandamide also promoted the polarization of naïve T cells towards a Th1 phenotype. Discussion: Our results show that anandamide has nuanced effects on the differentiation, maturation, cytokine secretion, metabolism and function of activated moLCs. Among these changes the decrease in CD1a expression on moLCs holds promise to selectively dampen inflammation induced by CD1a restricted T cells, which have been implicated as drivers of inflammation in common inflammatory skin conditions such as psoriasis, atopic dermatitis and contact dermatitis.

Integrated Analysis of CD1A Immune Infiltration and Competing Endogenous RNA Networks in COAD.

Background: The CD1A gene, a key component of the human immune system and part of the CD1 family, plays a crucial role in presenting lipid antigens to T cells. Abnormal CD1A expression is associated with various immune-related diseases and tumors. However, the biological function of CD1A in COAD is unclear. Methods: Multiple databases were systematically employed to conduct an analysis of CD1A expression in pan-cancer and COAD, along with its clinical-pathological features. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) functional enrichment analyses of CD1A were performed using the 'clusterProfiler' package. The Protein-protein interaction (PPI) analysis of CD1A was used the STRING database. Additionally, TIMER and ssGSEA tools were used to explore the relationship between CD1A expression in COAD and immune cell infiltration. The study also investigated the association between CD1A expression and N6-methyladenosine (m6A) modification genes in the TCGA COAD cohort and constructed a CD1A-centric competing endogenous RNA (ceRNA) regulatory network. Results: CD1A displays varying expression levels in various tumors, including COAD, and is closely linked to clinical-pathological characteristics. GO analysis suggests that CD1A plays a role in important processes like antigen processing and presentation, leukocyte-mediated immunity, and lymphocyte-mediated immunity. KEGG analysis identifies CD1A's involvement in key pathways such as the Chemokine signaling pathway and Cytokine-cytokine receptor interaction. PPI analysis highlights CD1A's interactions with CD207, CD1C, CD1E, FOXP3, and ITGB2. ssGSEA analysis indicates a significant relationship between CD1A expression and the infiltration of various immune cells in COAD. Significant associations were found between CD1A and m6A modification genes in COAD. Furthermore, a CD1A-centered ceRNA regulatory network has been constructed. Conclusion: CD1A emerges as a potential biomarker for the diagnosis and treatment of COAD, showing a strong association with tumor immune infiltration, m6A modification, and the ceRNA network.

Pulmonary Langerhans Cell Histiocytosis Post-Hodgkin Lymphoma Completely Resolved With Vinblastine in a Heavy Smoker: Coincidence or Causation?

The association among Langerhans cell histiocytosis, hematolymphoid malignancies, and heavy smoking has been addressed in medical literature to identify a possible potential link. Such occurrence can pose diagnostic challenges, as well as important clinical implications for disease progression and treatment approaches. We present pulmonary Langerhans cell histiocytosis instance in a 35-year-old male patient, with a 34-pack-year smoking history and nodular sclerosing Hodgkin lymphoma stage IIB who developed multiple bilateral lung nodules. The patient completed 6 cycles of doxorubicin (Adriamycin), bleomycin, vinblastine, and dacarbazine chemotherapy and radiotherapy 2 years earlier. CT chest scans revealed numerous micronodules scattered randomly throughout the upper and lower left lung lobes. Subsequent wedge resection exhibited cellular proliferation with grooved nuclei, eosinophilic cytoplasm, and surrounding inflammatory components. Immunohistochemical staining showed positive staining for S100 and CD1a confirming a diagnosis of pulmonary Langerhans cell histiocytosis. The patient responded to a 6-week treatment with vinblastine and prednisolone. A subsequent CT scan of the lungs revealed complete resolution after 3 years. This report underscores the importance of identifying pulmonary Langerhans cell histiocytosis in heavy smokers with Hodgkin lymphoma presenting with multiple nodular pulmonary lesions. For patients with Hodgkin lymphoma and a possible genetic predisposition, smoking may contribute to the overt development of pulmonary Langerhans cell histiocytosis. Therefore, smoking cessation and careful follow-up examinations are required. Further research is recommended to elucidate the underlying mechanisms of this intriguing association.

Keratinocyte-derived small extracellular vesicles supply antigens for CD1a-resticted T cells and promote their type 2 bias in the context of filaggrin insufficiency.

Introduction: Exosome-enriched small extracellular vesicles (sEVs) are nanosized organelles known to participate in long distance communication between cells, including in the skin. Atopic dermatitis (AD) is a chronic inflammatory skin disease for which filaggrin (FLG) gene mutations are the strongest genetic risk factor. Filaggrin insufficiency affects multiple cellular function, but it is unclear if sEV-mediated cellular communication originating from the affected keratinocytes is also altered, and if this influences peptide and lipid antigen presentation to T cells in the skin. Methods: Available mRNA and protein expression datasets from filaggrin-insufficient keratinocytes (shFLG), organotypic models and AD skin were used for gene ontology analysis with FunRich tool. sEVs secreted by shFLG and control shC cells were isolated from conditioned media by differential centrifugation. Mass spectrometry was carried out for lipidomic and proteomic profiling of the cells and sEVs. T cell responses to protein, peptide, CD1a lipid antigens, as well as phospholipase A2-digested or intact sEVs were measured by ELISpot and ELISA. Results: Data analysis revealed extensive remodeling of the sEV compartment in filaggrin insufficient keratinocytes, 3D models and the AD skin. Lipidomic profiles of shFLGsEV showed a reduction in the long chain (LCFAs) and polyunsaturated fatty acids (PUFAs; permissive CD1a ligands) and increased content of the bulky headgroup sphingolipids (non-permissive ligands). This resulted in a reduction of CD1a-mediated interferon-γ T cell responses to the lipids liberated from shFLG-generated sEVs in comparison to those induced by sEVs from control cells, and an increase in interleukin 13 secretion. The altered sEV lipidome reflected a generalized alteration in the cellular lipidome in filaggrin-insufficient cells and the skin of AD patients, resulting from a downregulation of key enzymes implicated in fatty acid elongation and desaturation, i.e., enzymes of the ACSL, ELOVL and FADS family. Discussion: We determined that sEVs constitute a source of antigens suitable for CD1a-mediated presentation to T cells. Lipids enclosed within the sEVs secreted on the background of filaggrin insufficiency contribute to allergic inflammation by reducing type 1 responses and inducing a type 2 bias from CD1a-restricted T cells, thus likely perpetuating allergic inflammation in the skin.

Immunohistochemical analysis of chronic and recurrent dermatophytosis.

BACKGROUND: Dermatophytosis has assumed epidemic proportions with rising resistance, recalcitrance and recurrence, especially in tropical regions. While various factors contribute to high prevalence worldwide, yet little is known about the interactions between host defence mechanisms and dermatophytes, particularly in chronic and recalcitrant dermatophytosis. OBJECTIVES: We aimed to compare the population of various immune cells in specimens of chronic recurrent dermatophytosis and those with acute superficial dermatophytosis. METHODS: We investigated the density of various immune cells-Langerhans cells (CD1a+), macrophages (CD68+), dermal dendrocytes (Factor XIIIa+) in the skin of chronic dermatophytosis patients and those with successfully resolved lesions (controls). RESULTS: Langerhans cells were significantly decreased in the epidermis of patients, both in affected and unaffected areas in comparison with controls. In the dermis, however, no differences in the density of immune cells (macrophages and fibroblasts) were observed. LIMITATIONS: The limited sample size and immune cells evaluated could be expanded further in future research. CONCLUSION: These results indicate that the decreased number of Langerhans cells could be a potential risk factor for the development of chronic and recurrent dermatophytosis.

Chemoradiotherapy and Lymph Node Metastasis Affect Dendritic Cell Infiltration and Maturation in Regional Lymph Nodes of Laryngeal Cancer.

Dendritic cells (DCs) are the most specialized antigen-presenting cells, and lymph nodes (LNs) play an important role in the DC-mediated T-cell response. We evaluated the infiltration of CD1a-positive DCs (CD1a-DCs), i.e., immature DCs, and S100-positive dendritic cells (S100-DCs), a mixture of immature and mature DCs, in 73 cases of laryngeal cancer and its regional LNs. Among them, 31 patients underwent radiotherapy (RT) or chemoradiotherapy (CRT) prior to surgery. No significant difference was found for CD1a-DC infiltration in the primary tumors, metastatic LNs and non-metastatic LNs, while S100-DCs were significantly fewer in number in the primary tumors and metastatic LNs compared to non-metastatic LNs. The cases which showed a high infiltration of S100-DCs in the metastatic LNs appeared to show a favorable prognosis, although statistical significance was not reached. In the RT/CRT group, the infiltration of the CD1a-DCs and S100-DCs was less in the primary tumors and metastatic LNs compared to the treatment-naive group. Conversely, the RT/CRT group showed higher CD1a-DC and S100-DC numbers in the non-metastatic LNs compared to the treatment-naïve group. Thus, DC maturation in metastatic LNs plays an important role in tumor immunity in laryngeal cancer, and the infiltration of DCs into the primary tumor and metastatic LNs is impaired by RT/CRT.

Relation of Langerhans cell size to buccal carcinoma.

Oral cancer decreases quality of life despite timely medical management. The carcinogens in tobacco products and their role in tumorigenesis are well documented. Langerhans cells (LCs) are a subset of antigen-presenting cells (APCs) that monitor the tumor microenvironment and engulf carcinogens and foreign bodies. We investigated the distribution and size of LCs and their relation to the mode of tobacco consumption and clinical outcome in patients with buccal carcinoma. We recruited patients with oral cancer who were scheduled for tumor excision and men with urethral stricture undergoing substitution urethroplasty using buccal mucosa. Normal and tumor-adjacent tissues were stained with CD1a antibody. The distribution and mean diameter of 100 LCs/patient were determined. We found significantly smaller LCs in patients who chewed only tobacco compared to those who consumed tobacco by other means. The size of LCs decreased significantly with progressive stages of malignant disease. We found that patients with larger LCs survived longer than those with smaller LCs during an average follow-up of 24 months. We suggest a relation between the size of LCs and clinical outcomes in patients with buccal carcinoma.

Human Skin T Cells Express Conserved T-Cell Receptors that Cross-React with Staphylococcal Superantigens and CD1a.

Human Langerhans cells highly express CD1a antigen-presenting molecules. To understand the functions of CD1a in human skin, we used CD1a tetramers to capture T cells and determine their effector functions and TCR patterns. Skin T cells from all donors showed CD1a tetramer staining, which in three cases exceeded 10% of skin T cells. CD1a tetramer-positive T cells produced diverse cytokines, including IL-2, IL-4, IL-5, IL-9, IL-17, IL-22, and IFN-γ. Conserved TCRs often recognize nonpolymorphic antigen-presenting molecules, but no TCR motifs are known for CD1a. We detected highly conserved TCRs that used TRAV34 and TRBV28 variable genes, which is a known motif for recognition of staphylococcal enterotoxin B, a superantigen associated with atopic dermatitis. We found that these conserved TCRs did not respond to superantigen presented by CD1a, but instead showed a cross-reactive response with two targets: CD1a and staphylococcal enterotoxin B presented by classical major histocompatibility complex II. These studies identify a conserved human TCR motif for CD1a-reactive T cells. Furthermore, the demonstrated cross-reaction of T cells with two common skin-specific stimuli suggests a candidate mechanism by which CD1a and skin flora could synergize during natural immune response and in Staphylococcus-associated skin diseases.

Langerhans Cell Histiocytosis of the Nose and Maxilla: A Rare Presentation.

Langerhans cell histiocytosis (LCH) is a disease characterized by localized and generalized proliferation of the histiocytes. It is a locally aggressive condition. The clinical presentation is highly variable and can range from isolated, self-healing skin or bone lesions to life-threatening multisystem disease. It can present as a unifocal or multifocal disease. The majority are present in the head and neck region, but the involvement of Paranasal sinuses is rare. Here we describe a 64-years-old female who presented with a slow-growing left nasal mass for 1 year. Evaluation of the patient was suggestive of malignancy, but the biopsy report turned out to be Langerhans cell histiocytosis; subsequently left, total maxillectomy was done. We hereby present a unique case of LCH with isolated nose and paranasal sinus involvement.

Dendritic Cell Subpopulations Are Associated with Prognostic Characteristics of Breast Cancer after Neoadjuvant Chemotherapy-An Observational Study.

Breast cancer (BC) is the most prevalent malignancy in women and researchers have strived to develop optimal strategies for its diagnosis and management. Neoadjuvant chemotherapy (NAC), which reduces tumor size, risk of metastasis and patient mortality, often also allows for a de-escalation of breast and axillary surgery. Nonetheless, complete pathological response (pCR) is achieved in no more than 40% of patients who underwent NAC. Dendritic cells (DCs) are professional antigen-presenting cells present in the tumor microenvironment. The multitude of their subtypes was shown to be associated with the pathological and clinical characteristics of BC, but it was not evaluated in BC tissue after NAC. We found that highe r densities of CD123+ plasmacytoid DCs (pDCs) were present in tumors that did not show pCR and had a higher residual cancer burden (RCB) score and class. They were of higher stage and grade and more frequently HER2-negative. The density of CD123+ pCDs was an independent predictor of pCR in the studied group. DC-LAMP+ mature DCs (mDCs) were also related to characteristics of clinical relevance (i.e., pCR, RCB, and nuclear grade), although no clear trends were identified. We conclude that CD123+ pDCs are candidates for a novel biomarker of BC response to NAC.

CD1a and bound lipids drive T-cell responses in human skin disease.

In addition to serving as the main physical barrier with the outside world, human skin is abundantly infiltrated with resident αß T cells that respond differently to self, infectious, microbiome, and noxious stimuli.  To study skin T cells during infection and inflammation, experimental biologists track T-cell surface phenotypes and effector functions, which are often interpreted with the untested assumption that MHC proteins and peptide antigens drive measured responses.  However, a broader perspective is that CD1 proteins also activate human T cells, and in skin, Langerhans cells (LCs) are abundant antigen presenting cells that express extremely high levels of CD1a.  The emergence of new experimental tools, including CD1a tetramers carrying endogenous lipids, now show that CD1a-reactive T cells comprise a large population of resident T cells in human skin.  Here, we review studies showing that skin-derived αß T cells directly recognize CD1a proteins, and certain bound lipids, such as contact dermatitis allergens, trigger T-cell responses. Other natural skin lipids inhibit CD1a-mediated T-cell responses, providing an entry point for the development of therapeutic lipids that block T-cell responses. Increasing evidence points to a distinct role of CD1a in type 2 and 22 T-cell responses, providing new insights into psoriasis, contact dermatitis, and other T-cell-mediated skin diseases.

Dendritic Cell Subpopulations Are Associated with Morphological Features of Breast Ductal Carcinoma In Situ.

Ductal carcinoma in situ (DCIS) is the preinvasive form of breast cancer (BC). It is disputed whether all cases of DCIS require extensive treatment as the overall risk of progression to BC is estimated at 40%. Therefore, the crucial objective for researchers is to identify DCIS with significant risk of transformation into BC. Dendritic cells (DC) are professional antigen presenting cells and as such play a pivotal role in the formation of immune cells that infiltrate in breast tumors. The aim of this study was to investigate the relationship between the density of DCs with different superficial antigens (CD1a, CD123, DC-LAMP, DC-SIGN) and various histopathological characteristics of DCIS. Our evaluation indicated that CD123+ and DC-LAMP+ cells were strongly associated with maximal tumor size, grading and neoductgenesis. Together with CD1a+ cells, they were negatively correlated with hormonal receptors expression. Furthermore, the number of DC-LAMP+ cells was higher in DCIS with comedo necrosis, ductal spread, lobular cancerization as well as comedo-type tumors, while CD1a+ cells were abundant in cases with Paget disease. We concluded that different subpopulations of DCs relate to various characteristics of DCIS. Of the superficial DCs markers, DC-LAMP seems particularly promising as a target for further research in this area.

DNA hypomethylation silences anti-tumor immune genes in early prostate cancer and CTCs.

Cancer is characterized by hypomethylation-associated silencing of large chromatin domains, whose contribution to tumorigenesis is uncertain. Through high-resolution genome-wide single-cell DNA methylation sequencing, we identify 40 core domains that are uniformly hypomethylated from the earliest detectable stages of prostate malignancy through metastatic circulating tumor cells (CTCs). Nested among these repressive domains are smaller loci with preserved methylation that escape silencing and are enriched for cell proliferation genes. Transcriptionally silenced genes within the core hypomethylated domains are enriched for immune-related genes; prominent among these is a single gene cluster harboring all five CD1 genes that present lipid antigens to NKT cells and four IFI16-related interferon-inducible genes implicated in innate immunity. The re-expression of CD1 or IFI16 murine orthologs in immuno-competent mice abrogates tumorigenesis, accompanied by the activation of anti-tumor immunity. Thus, early epigenetic changes may shape tumorigenesis, targeting co-located genes within defined chromosomal loci. Hypomethylation domains are detectable in blood specimens enriched for CTCs.

OSCC in Never-Smokers and Never-Drinkers Is Associated with Increased Expression of Tumor-Infiltrating Lymphocytes and Better Survival.

The aim of this study was to investigate the clinical, histopathologic, and immunologic differences of oral squamous cell carcinoma of never-smokers/never-drinkers and smokers/drinkers. Immunohistochemical staining for CD4, CD8, FoxP3, CD1a, and p16 was performed in 131 oral squamous cell carcinomas from smokers/drinkers and never-smokers/never-drinkers. Associations of smoking/drinking status with clinicopathologic data, immunohistochemical antibody expression, and survival were examined. Oral squamous cell carcinoma in never-smokers/never-drinkers was associated with the female gender (p < 0.001). Never-smokers/never-drinkers were older at diagnosis than smokers/drinkers (p < 0.001). Never-smokers/never-drinkers had more tumors in the maxilla, mandible, and tongue (p < 0.001). Pre-existing oral potentially malignant disorders appeared to be more common in never-smokers/never-drinkers (p < 0.001). Perineural invasion was more common in smokers/drinkers (p = 0.039). Never-smoking/never-drinking was associated with better overall survival (p = 0.004) and disease-specific survival (p = 0.029). High CD4+ T cell infiltration was associated with never-smoking/never-drinking (p = 0.008). Never-smokers/never-drinkers also showed increased CD8+ T cell infiltration (p = 0.001) and increased FoxP3+ Treg infiltration (p = 0.023). Furthermore, the total group of tumor-infiltrating lymphocytes was associated with never smoking/never drinking (p = 0.005). To conclude oral squamous cell carcinoma of the never-smokers/never-drinkers appears to be a distinct type of tumor, as it appears to have unique clinical and pathologic features and a more immunogenic microenvironment.

Dendritic Cell Activation in Leprosy Using CD1a and Factor XIIIa Markers.

BACKGROUND: Leprosy is manifested in varied forms based on the immune status of the patient giving rise to the polar and borderline spectrum of tuberculoid (TT) and lepromatous leprosy (LL). The present study was conducted to assess the macrophage activation in the spectrum of leprosy using CD1a and Factor XIIIa immunohistochemical markers and to correlate the macrophage expression with the morphological spectrum and bacillary index. METHODOLOGY: The present study was an observational study. RESULTS: The present study consisted of 40 biopsy-proven leprosy cases, in which a majority were males, and the most common age group was 20-40 years. The most common type encountered was borderline tuberculoid (BT) leprosy. Expression of epidermal dendritic cells and intensity of staining by CD1a was higher in TT (seven of 10 cases (70%)) when compared to LL (one of three cases (33%)). Similarly, Factor XIIIa showed higher expression of dermal dendritic cells in 90% of TT when compared to LL which was seen in 66%. CONCLUSION: The increased number and strong intensity of dendritic cells in the tuberculoid spectrum may indirectly indicate macrophage activation and possibly account for the low bacillary index.

Langerhans cell histiocytosis: A diagnostic challenge on thyroid fine needle aspiration cytology.

Thyroid gland involvement by Langerhans cell histiocytosis (LCH) is extremely rare. A 28-year-old woman with a history of polyuria, polydipsia and amenorrhoea presented with a diffuse thyroid swelling of 2 months duration. Clinical diagnosis was diabetes insipidus. Endocrine profile was normal. Fine needle aspiration cytology (FNAC) from thyroid revealed numerous large histiocytes with prominent nuclear grooves against an inflammatory background rich in eosinophils. A diagnosis of LCH was made and immunocytochemistry with CD1a confirmed the same. Subsequent skin biopsy also showed LCH. FNAC diagnosis of LCH in thyroid is challenging. The diagnostic pitfalls range from thyroiditis due to the presence of inflammatory cells in the background to papillary thyroid carcinoma due to grooved nuclei. Additional material should be collected at FNAC for ancillary studies to confirm the diagnosis.

Concomitant Langerhans and Interdigitating Reticulum Cell Hyperplasia in a Reactive Lymph Node of an Infant with Omenn Syndrome: A Diagnostic Pitfall for Langerhans Cell Histiocytosis.

Omenn syndrome, a rare form of combined immunodeficiency in infants, presenting with recurrent infections, erythroderma, lymphadenopathy, hepatosplenomegaly, eosinophilia, and increased serum IgE levels. It is a fatal condition unless treated by hematopoietic stem cell transplant. Hence, an early diagnosis and a prompt treatment can lead to better outcome in these unfortunate babies afflicted with Omenn syndrome. Here, we present an 8-week-old infant with typical features of Omenn syndrome, both clinically as well as on laboratory analysis, but surprising immunohistochemical findings on lymph node biopsy.