Cytological diagnosis of Langerhans cell histiocytosis with cutaneous involvement.

Langerhans cell histiocytosis (LCH) is a rare disease affecting predominantly children. The course of the disease varies, from spontaneous resolution to a progressive multisystem disorder with organ dysfunction and potential life-threatening complications. Diagnosis of LCH is often difficult and may be delayed because of its rarity and especially so if it occurs with unusual presentation. Fine needle aspiration cytology of a 4 year old male child, a case of LCH is presented with a purpose of highlighting the characteristic cytological features. A high index of suspicion, awareness of characteristic cytological features of LCH and its differential diagnoses is necessary. This can obviate the need of biopsy and electron microscopy. Immunohistochemistry if available can be performed on cytology smear and cell block.

Introduction

Langerhans cell histiocytosis (LCH) is a rare disease arising from clonal proliferation of Langerhans cell, abnormal cells derived from bone marrow that migrates from skin to lymph node. In 1868, Paul Langerhans discovered the epidermal dendritic cells. Diagnosis of LCH is often difficult and can be delayed because of its rarity. The course of the disease varies, from spontaneous resolution to a progressive multisystem disorder with organ dysfunction and potential life threatening complications.[12] We present a case of LCH in a child where fine needle aspiration cytology (FNAC) was helpful in establishing a rapid and correct diagnosis in correlation with radiology. The purpose is to highlight common and characteristic cytological features.

Case Report

A 4 year old male child presented with diffuse cervical swelling on the left side of the neck since 2 months. There were multiple eczematous lesions seen over the swelling. On examination, multiple cervical lymph nodes were palpable measuring 0.8 × 0.8 to 1.2 × 1.5 cm on the anterior neck on both the sides of the neck. They were firm, tender and slightly mobile. Patient also had history of left ear discharge since 2 weeks. He had no fever or loss of weight. Liver and spleen were not palpable. There was no history of Koch's contact.

On investigation his hemoglobin was 11.5 g/dL. Total leukocyte count was 12,080 with differential count showing 45% neutrophils, 37% lymphocytes, 15% monocytes and 3% eosinophils. Platelet count was normal. The Mantoux test was negative. The bone marrow biopsy was unremarkable. Skeleton X-ray survey revealed no abnormality. Positron emission tomography (PET) scan showed conglomerate nodal mass in left II, III, II/V level and left supraclavicular nodal mass extending upto superior mediastinum and left chest wall. There were no lytic lesions seen in the skeleton system. Thyroid was normal.

The patient was referred for FNAC. FNAC from diffused selling over left supraclavicular region yielded hemorrhagic whitish aspirate. Ethanol fixed smears and air dried smears were prepared and stained with Papanicolaou and Giemsa stains respectively. Cytological smears were cellular and showed numerous atypical histiocytes singly and in loose cohesive clusters. These histiocytes were binucleate, multinucleate with abundant dense cytoplasm and eccentric vesicular nuclei [Figure 1a-c]. The nuclei showed characteristic intranuclear pseudoinclusions, prominent nuclear indentations and grooves (with a kidney or coffee bean appearance) [Figure 1b]. The background showed lymphocytes, neutrophils and few eosinophils [Figure 1a]. The presumptive diagnosis of Langerhans cell histiocytosis was given.

Figure 1

(a) Cellular smear showing loose clusters of cells with preponderance of histiocytes with few of them showing kidney shaped nucleus (arrow), alongwith neutrophils (N), lymphocytes (L) in the background. (Pap, ×400); (b) Cells showing pseudoinclusion (arrow) (Pap, ×400); (c) Binucleated histiocyte (arrow) (Giemsa, ×400)

The differential diagnoses entertained were Hodgkin's lymphoma and Langerhans cell histiocytosis. Subsequently biopsy was done.

The biopsy showed sheets of atypical histiocytes with grooves with polymorphous inflammatory cells comprising of eosinophils, neutrophils, lymphocytes in background. There was no necrosis, and no mitosis [Figure 2a]. The immunohistochemistry was performed. On immunohistochemical staining, S-100 and CD1a were diffusely positive in all the atypical histiocytes [Figure 2b]. Desmin and ALK-1 were negative. The final diagnosis of Langerhans cell histiocytosis was given (Low risk).[34]

Figure 2

(a) Biopsy showing variable histiocytes with mononucleate, binucleate and multinucleate cells amidst lymphocytes and polymorphs (H and E, ×400); (b) Immunostaining with S100 showed diffuse positivity in the atypical histicytes (IHC, ×100)

The patient was treated with vinblastine, etoposide and prednisolone. After 4 months, the swellings decreased and all the eczematous lesions healed completely.

Discussion

LCH is a rare disease and the estimated annual incidence ranges from 0.5 to 5.4 cases per million persons. In the past, the disorder was referred to as histiocytosis X and had 3 variants: eosinophilic granuloma, Hand-Schuller Christian disease and Letterer – Siwe syndrome. These three conditions are believed to represent different expressions of the same disorder, now known as LCH.[1]

An ongoing debate exists whether this is reactive or neoplastic process.[56] The disease is characterized by clonal proliferation of the antigen presenting dendritic cell called Langerhans cell (LC). The proliferation may be induced by a viral infection, a defect in T-cell macrophage interaction and/or a cytokine driven process mediated by tumor necrosis factor, interleukin 11 and leukemia inhibitory factor 1.[1]

LCH may occur at any age although the majority of the cases are diagnosed in children from newborn to 15 years. There is no significant gender difference. The clinical spectrum varies from a solitary lesion to multifocal unisystem to multisystem lesions with related symptoms. The unifocal form usually involves the bone, often seen in children in between 5 and 15 years old. Systemic LCH is more common in children under 2 years of age. The multifocal unisystem form almost always occurs in the bone. Any bone can be involved, but more than 50% of lesions occur in the skull, spine, pelvis, ribs and mandible. The multifocal multisystem form involves many organs, including the bone, skin, liver, spleen, hematopoietic system and lymph node.[126] The lymph node involvement in LCH can be seen as a part of the systemic disease or as a localized lesion.[56]

Our case showed only skin lesions in the supraclavicular area which exhibited features suggestive of eczema.[45] The lymph node enlargement seen in X-ray was reaction to skin lesion.[5] Isolated skin lesion in LCH is a rare clinical presentation.[2]

Traditionally, the diagnosis of LCH is based on hematologic and histological criteria.[1-3] Enough experience has accumulated in accurate cytological diagnosis of LCH in various body sites on the basis of characteristics cytological features in the presence of appropriate clinical and radiological setting as evident from several case reports and case series.[267] Ancillary studies may be always necessary for diagnosis in appropriate clinical and radiological setting. However, our patient had no other systemic involvement which was evident from the investigations done. Hemogram, hepatic function test, inflammatory markers, skeletal radiography, chest X-ray, PET scan and abdomen ultrasonography did not show any other organ involvement. Hence biopsy of the skin lesion and further IHC studies were done which confirmed the diagnosis of LCH.

The classic cytological features include high cellularity composed of sheets and many Langerhans cell seen admixed with polymorphous population of numerous eosinophils neutrophils and lymphocytes, multinucleated giant cells and macrophages. The key to the diagnosis is to identify Langerhans cell through its characteristics features namely large cells with large, eccentric, kidney-shaped coffee bean nucleus.[289] A confirmed diagnosis can only be made if cells are labeled with anti-CD1a antibody.

Malignancy with tumor cells commonly having nuclear grooves or pseudo inclusions should also be considered, such as malignant melanoma and papillary carcinoma of thyroid. LCH show positivity for S-100, PNA (peanut agglutinin), MCH class II, CD1a and Langerin (CD 207).[1] Our case showed positivity for S-100 proteins and CD1a.

The Birbeck granules are their distinctive ultrastructural hallmark.[1] Electron microscopy though specific, is more time consuming and costly. It is not considered essential for diagnosis as suggested by other authors. The patient with apparently restricted LCH needs careful staging of their disease to ensure that these are not part of a more extensive process. FNA can be used to establish the extent of disease or recurrence of LCH. The patient with apparently restricted LCH needs careful staging of their disease to ensure that these are not part of a more extensive process. FNA can be used to establish the extent of disease or recurrence of LCH.

Conclusion

A high index of suspicion, awareness of characteristic cytological features of LCH, and its differential diagnoses is necessary. This can obviate the need of biopsy and electron microscopy. IHC if available can be performed on cytology smear and cell block.