Painless postauricular mass: An atypical presentation of Kikuchi-Fujimoto disease

Abstract

Kikuchi-Fujimoto disease, also known as histiocytic necrotizing lymphadenitis, is a rare self-limiting condition primarily characterized by cervical lymphadenopathy and fever. This report presents the case of a Han Chinese woman in her early 40s who had no significant medical history and presented with a painless mass behind her ear. She denied systemic symptoms such as fever, night sweats, or weight loss. Physical examination revealed a non-tender, mobile mass in the postauricular region. Initial ultrasound suggested a small cystic structure, and the mass was subsequently excised. Initial pathology reported reactive lymphoid hyperplasia; however, due to atypical presentation, immunohistochemical staining was performed, which was positive for multiple markers consistent with Kikuchi-Fujimoto disease. The patient did not receive specific treatment and remained asymptomatic with no recurrence at 1-month follow-up. The patient lacked typical lymph node pain and fever. The absence of typical lymph node pain and fever in the patient in this case highlights the importance of considering Kikuchi-Fujimoto disease in the differential diagnosis of painless lymphadenopathy and underscores the significance of histopathological examination and immunohistochemical analysis in reaching a definitive diagnosis.

Introduction

Kikuchi-Fujimoto disease (KFD), first described in 1972 by Kikuchi and Fujimoto, is a rare benign condition characterized by fever and tender cervical lymphadenopathy. ¹ Although typically self-limiting, KFD can present a diagnostic challenge due to its non-specific symptoms, which may mimic more serious conditions such as lymphoma or tuberculosis. The etiology of KFD remains elusive, but it is hypothesized to involve a viral trigger or an autoimmune response in genetically predisposed individuals. ² This disease is more commonly reported among young adults of Asian descent, although cases have been documented worldwide. ³

The clinical presentation of KFD often includes fever and cervical lymphadenopathy and sometimes rash, arthralgia, and fatigue. ⁴ However, atypical manifestations can occur, leading to misdiagnoses. For instance, KFD has been reported to involve extranodal sites and present without the classic lymphadenopathy, complicating diagnosis. ⁵ The gold standard for diagnosing KFD is a lymph node biopsy, which reveals characteristic histiocytic and lymphocytic infiltration. Immunohistochemical (IHC) staining aids in diagnosing KFD by identifying specific markers within affected tissues, such as CD8+ T cells and CD68+ histiocytes, which help distinguish it from other lymphadenopathies. ⁶ While KFD is generally a benign condition with a favorable prognosis, there is a recognized association with the development of systemic lupus erythematosus (SLE) in a small subset of cases. ⁷ This association underscores the importance of long-term follow-up for patients with KFD to monitor for potential autoimmune complications.

Case presentations

The reporting of this study conforms to CARE guidelines. ⁸

A Han Chinese woman in her early 40s with no significant medical history presented to our outpatient clinic with a painless mass behind her right ear that had been present for approximately 3 weeks. She denied any history of autoimmune diseases, fever, night sweats, weight loss, or other systemic symptoms. There was no family history of autoimmunity or consanguineous marriage between her parents. She was fully vaccinated and had no allergies. No recent travel history or contact with patients with tuberculosis was reported. On physical examination, the patient’s vital signs were within normal limits: temperature, 36.5°C; heart rate, 72 beats per minute; respiratory rate, 16 breaths per minute; blood pressure, 118/76 mmHg. She appeared well-nourished and in no distress, with no signs of weight loss or muscle wasting. Cardiovascular examination revealed regular heart sounds without murmurs, and respiratory examination showed clear lung fields with normal breath sounds. Abdominal examination was unremarkable, with no hepatosplenomegaly or tenderness. Neurological examination was normal, with intact cranial nerves, normal motor and sensory function, and symmetric reflexes. Musculoskeletal examination showed no joint abnormalities or muscle weakness. Lymphatic system examination revealed a single, non-tender, mobile mass measuring approximately 1.5 cm in diameter in the right postauricular region, with no other palpable lymphadenopathy. An ultrasonographic examination of the affected area revealed a small cystic structure, initially suspected to be an epidermoid cyst. However, given the clinical presentation and location, further evaluation was deemed necessary. The mass was subsequently excised. Preliminary pathological results showed that the structure of lymph nodes was generally normal, with mild focal necrosis in cortical and paracortical areas, accompanied by proliferation of lymphocytes and histiocytes, and lack of neutrophils and plasma cells (Figure 1(a) and (b)). Immunohistochemical staining showed CD68+ histiocytes, CD3+ T cells, and CD20+ B cells; the distribution of T cells and B cells was generally normal (Figure 2). Based on these pathological findings, the pathologist made a diagnosis of Kikuchi’s disease. Other conditions such as SLE, viral infections, bacterial infections, tuberculosis, and lymphoma should also be considered. After receiving the immunohistochemistry results, the patient underwent a complete blood cell count and autoantibody tests, with no positive results. Due to the absence of significant discomfort, the patient declined further hematological examinations and bone marrow aspiration. The patient did not receive any medication for treatment. She remained asymptomatic with no recurrence at 1-month follow-up.

Figure 1.

Node histopathology. (a) Nodal paracortical expansion resulting in general architecture derangement (H&E, 40×) and (b) presence of lymphoid cells in different maturing stages, histiocytes, and areas of necrosis (H&E, 200×). H&E: hematoxylin and eosin.

Figure 2.

Immunohistochemistry analysis showing macrophages stained positive to CD10, BCL-6, BCL-2, CD5, CD3, CD20, CD21, MPO, CD123, and CD68.

Discussion and conclusion

KFD is a benign condition that typically presents with painful cervical lymphadenopathy and fever. The disease is often self-limiting, but its atypical presentations can lead to diagnostic challenges. ⁹ As this case demonstrates, the patient did not present with fever and tender cervical lymphadenopathy. Without subsequent pathological and immunohistochemical analysis, the initial ultrasound findings of small cystic structures may lead to misdiagnosis. This highlights the importance of thorough histopathological examination and the use of immunohistochemistry in diagnosing KFD. The patient’s clinical presentation may represent a mild form of the disease. Given the self-limiting nature of the condition, many patients with mild symptoms may not seek medical attention, suggesting that many mild cases may remain undetected.

The etiology of KFD is unknown, with reports speculating a correlation with viral or parasitic infections. ¹⁰ Unfortunately, due to the absence of significant discomfort symptoms, the patient refused further hematological examinations beyond the complete blood cell count and autoantibody tests. Some case reports have documented the co-occurrence of KFD with SLE. In the majority of longitudinal evaluations, KFD occurs prior to SLE, although there are also reports of its occurrence after SLE. ¹¹ However, the current evidence is insufficient to establish a mutual association between the two as autoimmune diseases. The patient’s non-recurrent and benign course is consistent with the typical prognosis of KFD, but long-term follow-up is still required to monitor the potential development of autoimmune diseases.

The treatment for KFD is primarily supportive, as the disease is usually self-limiting. However, in cases with severe symptoms or complications, treatment may include the use of non-steroidal anti-inflammatory drugs, corticosteroids, or other immunomodulatory therapies. ¹² The decision to initiate treatment is often based on the severity of symptoms and the presence of any complications. Despite the lack of high-level evidence guiding treatment, these approaches have been used to alleviate symptoms and potentially shorten the disease course.

This case report describes an atypical presentation of KFD, highlighting the importance of a thorough histopathological examination and IHC analysis in reaching a definitive diagnosis. The case also serves as a reminder of the need for clinicians to consider KFD in their differential diagnosis of lymphadenopathy, even when the presentation is atypical or lacks the usual clinical signs. The management of KFD is primarily supportive, and most patients recover fully without sequelae. However, the potential for KFD to progress to SLE or other autoimmune diseases warrants careful monitoring and follow-up care.