Cytology of secondary hemophagocytic lymphohistiocytosis masquerading as lymphoma in a nonimmunocompromised adult.

Hemophagocytic lymphohistiocytosis (HLH) is a potentially fatal immune disorder which is uncommon in a nonimmunocompromised adult. A 27-year-old female who presented with fever, hematuria, generalized lymphadenopathy was clinically suspected to have lymphoma was subjected to fine needle aspiration of cervical lymph nodes. Cytology of lymph node had numerous histiocytes with phagocytosed lymphocytes, red blood cells and nuclear debris. A diagnosis of secondary HLH was made based on cytological findings, clinical manifestations, and laboratory results. She was treated with steroids and recovered completely. A high degree of clinical suspicion coupled with comprehensive cytology with fine needle aspiration cytology is fruitful in the diagnosis of HLH, a potentially fatal disease and help in the delineation of therapeutic regimen.

Introduction

Hemophagocytic lymphohistiocytosis (HLH) was earlier called as hemophagocytic syndrome. HLH was first described in 1939.[1] The incidence is approximately 1.2 cases/million/year.[2] HLH is broadly classified into two types based on the etiology (1) primary HLH caused by genetic mutations (2) secondary HLH as a result of other clinical conditions. There is a wide range of clinical manifestations like infections, malignant neoplasm, immunocompromised patients, rheumatic arthritis and metabolic conditions that can culminate into HLH.[34] The commonest cause is a viral infection[4] in children and immunocompromised status in adults.

In order to diagnose HLH, the “Histiocyte Society Trials – HLH 2004 criteria” has to be met.[5] It has no specific clinical feature or laboratory test other than the fine needle aspiration cytology (FNAC) that helps the clinician to arrive at a diagnosis. Here, we are presenting a rare case of secondary HLH in a nonimmunocompromised adult female due to viral etiology following FNAC of cervical lymph nodes with a clinical suspicion of lymphoma.

Case Report

A 27-year-old female presented with fever since 15 days associated with pain abdomen, dysuria, hematuria, hepatosplenomegaly and generalized lymphadenopathy. Her hematological investigations revealed bicytopenia with hemoglobin – 8.7 g/dL and platelet count – 64,000 cells/mm2; serological tests were positive for Weil Felix and Paul Bunnel, and negative for HIV; biochemical tests showed hypertriglyceridemia (triglycerides – 831 mg/dL), hyperferritinemia (1650 ng/mL), hyperbilirubinemia (direct bilirubin – 4.4 mg/dL, indirect bilirubin – 2.1 mg/dL), hypoalbuminemia (albumin – 2.6 g/dL, albumin/globulin ratio — 1:1), transaminitis (aspartate aminotransferase - 144U/L, alanine transaminase - 102U/L).

Rest of the tests were within normal limits. Abdominal ultrasound revealed additional findings of right renal calculi, periportal, peripancreatic, right iliac, pre and para aortic lymphadenopthy.

She gradually developed altered sensorium, with left cerebellar signs, reduced plantar reflexes and truncal ataxia due to central nervous system (CNS) involvement. Clinicians suspecting lymphoma requested for FNAC.

Fine needle aspiration cytology of bilateral cervical lymph node with 22G needle was performed, and smears were stained with May-Grünwald-Giemsa and Papanicolaou. Smears were highly cellular. Numerous histiocytes engulfing lymphocytes, red blood cells, plasma cells and nuclear debris in the cytoplasm with eccentrically placed, round nucleus were noted [Figure 1]. Lymphoid series of cells at various stages of maturation and plasma cells were seen. There were no acute inflammatory cells like neutrophils or eosinophils. Combining the FNAC findings, clinical features and laboratory results a diagnosis of HLH secondary to viral infection was made. Bone marrow also showed a few histiocytes with engulfment of blood cells along with micronormoblastic erythroid hyperplasia and mild megakaryocytic hyperplasia.

Figure 1

Numerous hemophagocytic histiocytes along with lymphoidseries of cells at various stages of maturation and plasma cells (H and E, ×100). Inset showing a hemophagocytic histiocyte engulfing lymphocytes, plasma cells, and nuclear debris in the cytoplasm with eccentrically placed nucleus (H and E, ×400)

Meanwhile, within a couple of hours the patient's condition worsened, she developed disseminated intravascular coagulopathy with prolonged prothrombin time, activated partial thromboplastin time and was positive for fibrin degradation products.

An intravenous steroid was started, and she showed an immediate good response to the treatment.

Discussion

The common clinical features of HLH are prolonged fever, hepatosplenomegaly, bleeding, skin rash, CNS abnormalities, and jaundice. The common laboratory findings include bicytopenia or pancytopenia, coagulopathy, hyperlipidemia, hypofibrinogenemia, hyperferritinemia, transaminitis, hyperbilirubinemia, hypoalbuminemia and hyponatremia.[3]

The most commonly affected organ is liver, hence at least increased transaminases is necessary to diagnose HLH. HLH can be confirmed by identifying the genetic mutations.[3] HLH is no longer viewed as a disorder of young children; adult patients are now being identified and treated.[6] HLH in adults is mostly due to an underlying disease like Epstein-Barr virus infection and lymphoma.

The pathogenesis involved in genetic mutation is that the cytotoxic cells form a conjugate with their target to form an immunologic synapse, followed by trafficking of the cytotoxic granules containing perforin and granzymes toward the immunologic synapse, docking, priming and fusion of the cytotoxic granules with the plasma membrane. Granule content is released into the immunologic synapse and induces target-cell destruction by caspase-dependent and independent apoptosis. In secondary HLH, there is failure to remove antigen, which results in ongoing stimulation of the immune effector cells.[3]

The cytological examination of bilateral cervical lymph nodes showed numerous histiocytes with hemophagocytosis that can be seen in lymphoma with benign erythrophagocytosis. But there were no atypical lymphoid cells hence lymphoma was ruled out. The differential diagnosis at this juncture was histiocytic disorders like Rosai-Dorfman (RD) disease, Langerhans cell histiocytosis (LCH), malignant histiocytosis and HLH [Table 1].

Table 1

Differential diagnosis of HLH

Rosai-Dorfman disease presents with bilateral massive and painless cervical lymphadenopathy with or without constitutional manifestation. It is a rare, but distinct clinico-pathological entity of idiopathic proliferation of histiocytes with a unique cytologic feature of histiocyte, which are large cells containing vesicular nucleus and voluminous cytoplasm, exhibiting lymphophagocytosis (emperipolesis). This patient even though had bilateral cervical lymphadenopathy, they were not massive and had hepatosplenomegaly that is unusual in RD disease.[7]

The classic cytological features of LCH include high cellularity, sheets of Langerhans cell 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 that has characteristics features namely large cell with large, eccentric, kidney-shaped coffee bean nucleus. LCH was ruled out because of absence of diagnostic findings such as eosinophils and lobulation or grooving of the nucleus.[8]

It may be difficult to distinguish between HLH and malignant histiocytosis because of similar clinical presentation; but low nucleocytoplasmic ratio, abundant lightly staining cytoplasm with hemophagocytosis, absence of prominent nucleoli and mitotic figures are the cytological features of HLH compared to malignant histiocytosis.[9] Considering the cytological findings, clinical presentation and laboratory findings the clinicians were able to arrive at a diagnosis of HLH.

For further confirmation of HLH, bone marrow study was requested. We could obtain bone marrow aspirate but were unable to acquire bone marrow biopsy. The smears showed occasional histiocytes with hemophagocytosis. Although the demonstration of hemophagocytosis in the bone marrow of lymph node is virtually diagnostic, negative results may be reported due to sampling difficulties or timing of the procedure.[10]

Conclusion

Fine needle aspiration cytology is an easy, cost effective, rapid and simple procedure. A high degree of clinical suspicion coupled with comprehensive cytology with FNAC is fruitful in the diagnosis of HLH, a potentially fatal disease and help in the delineation of therapeutic regimen. It is no longer a disease of children since it has also been detected in adults caused by various etiological agents.