Background

Filariasis is a tropical vector-borne disease seen predominantly in Asian, African, and some South American countries [1]. In India, it is distributed along the sea coast and bank of rivers and the endemic areas include Bihar followed by Kerala, Uttar Pradesh, and Tamil Nadu [1], West Bengal [2]. Lymphatic filariasis in humans is mainly caused by Wuchereria bancrofti and Brugia Malayi. The adult worm mainly affects lymphatic circulation (Fig. 1). The commonly involved sites are bronchial aspirates, cervicovaginal smears, and pericardial fluid [3].

Fig. 1
figure 1

Life cycle of Wuchereria bancrofti [3]

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Breast involvement in filariasis is an extremely rare disease, seen only in endemic areas. Involvement of the breast occurs when the larvae migrate to lymphatic vessels leading to gradual fibrosis causing disruption of local lymphatic drainage [4]. Disruption of the subdermal lymphatic drainage can lead to hyperemia and peau d’orange appearance—a sign of breast malignancy causing the clinical dilemma. Another common presentation of patients with breast filariasis is an ill-defined painless breast lump [1]. The most common involved site is the upper outer quadrant of the breast followed by the periareolar region. The clinical course is often insidious with occasional febrile or inflammatory episodes [4].

Due to vague clinical presentation and symptoms mimicking breast malignancy, diagnosing breast filariasis is challenging [5].

Imaging plays an important role in the diagnosis of breast filariasis with ultrasound being the modality of choice. Real-time ultrasound helps to demonstrate the vigorous movements of the filarial worm termed “filarial dance”—classical filariasis. “The filarial dance sign” was first coined by Amartal et al. in a patient with scrotal filariasis [6, 7].

Thus, an appropriate diagnosis with real-time ultrasound helps in appropriate treatment and also helps in reducing the psychological stress on the patient.

Case presentation

A 30-year-old patient from West Bengal presented to an outpatient surgery department, Sri Ramachandra Medical Centre, Chennai, Tamil Nadu, with a complaint of painless nodular swelling in the periareolar region of the right breast for the past 1 month associated with itching. The family history was negative for breast carcinoma. There was no history of breast trauma.

On clinical examination, there was no palpable lump in the breast and no palpable axillary lymph nodes. The overlying and adjacent skin was normal. The patient reported no symptoms of fever or chills.

Considering the age of 30 years, she underwent an ultrasound of both breasts as a primary investigation. Ultrasound of the right breast revealed a hypoechoic lesion in the subareolar region (area of palpable concern), around 11 o’ clock position measuring 1.2 × 0.6 cm probably a dilated duct with a tiny linear hyperechoic fluctuating focus within (Fig. 2). On real-time ultrasound, the vigorous movement of the worm was seen within the duct—suggestive of “Filarial dance” (Fig. 3). On color Doppler, mixed red-blue color signals with rhythmic, non-pulsatile Doppler signals were noted (Fig. 4). Ultrasound of the left breast was unremarkable.

Fig. 2
figure 2

Serial of images from real-time ultrasound focused on targeted lesion in the right breast at 11 o’ clock position

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Fig. 3
figure 3

a A tubular hypoechoic lesion in the subareolar region of the right breast around 11 o’ clock position suggestive of dilated duct. b A linear hyperechoic focus within the dilated duct. c Color Doppler showing mixed red-blue signals within

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Fig. 4
figure 4

Power Doppler of the curvilinear hyper echogenic area reveals non-rhythmic, non-pulsatile signal within

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Ultrasound-guided fine needle aspiration cytology of the dilated duct was done using an 18-gauge needle (Fig. 5). Wet and dry slides were made and sent for cytology. The cytology result revealed the presence of bancrofti microfilaria.

Fig. 5
figure 5

USG-guided FNAC from the dilated duct using a 18-gauge needle

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Blood investigations revealed normal hemoglobin levels 12.4 gms/dl (normal range 12-15gms/dl), red blood cell count of 4.42 mill/cc.mm (normal range 3.8–4.8 mill/cc.mm), a total leukocyte count of 7300 cells per microliter (normal range 4500–11,000 cells per microliter [4.5–11 cells × 109/l]), a normal differential leukocyte count (60% neutrophils [normal range, 40–80%], 23% lymphocytes [normal range, 20–40%], eosinophilia-with 10% eosinophils [normal range, 1–4%]), 6.2% monocytes [normal range,2–10%], 0.6% basophils [normal range,0–1%].

Peripheral blood smear revealed normocytic normochromic red blood cells with the normal number, morphology, and distribution of white blood cells with the absence of malarial parasite and microfilariasis.

Based on the ultrasound features and differential leukocyte showing eosinophilia, the diagnosis of breast filariasis was given.

The patient was put on a regimen of diethyl-carbamazine citrate (Day 1: 50 mg PO PC; Day 2: 50 mg PO TID; Day 3: 100 mg PO TID; Day 4–14: 100 mg TID PO) for 2 weeks for a period of 3 months with a drug-free interval of 2 weeks between each course.

The follow-up targeted ultrasound of the right breast performed after the completion of treatment showed a dilated duct in the subareolar region of the right breast. Twirling vigorous movement of the worm within the duct was no longer seen, suggestive of the dead worm. There was no evidence of mixed color signals on the color Doppler.

Conclusions

Breast filariasis is a rare presentation; however, in endemic areas like West Bengal, it is of utmost importance to differentiate breast filariasis from breast malignancy and correctly diagnose this disease using real-time ultrasound and color Doppler, thus helping inappropriate management.