General
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• Lymphatic filariasis is caused by nematodes that inhabit the lymphatic vessels and lymph nodes of a human host

Terminology
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• 3 filarial species cause lymphatic filariasis in humans:
  • Wuchereria bancrofti is the most common cause of infections worldwide
  • Brugia malayi and Brugia timori can be the causative organisms in Asia
  • Dirofilarial infection of the breast has also been reported (Breast Care (Basel) 2012;7:487)

Epidemiology
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• Endemic in Central Africa and South East Asia
• Humans are the only host for W. bancrofti filariasis
• Brugian filariasis can affect wild and domestic animals

Sites
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• Inguinal lymph nodes and lower extremities are most commonly involved
• Can affect the arms, breast and genitalia

Pathophysiology
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• Microfilaria enter the lymphatic vessels of mammary gland and develop into adult worms, disrupting lymphatic drainage
• Intact adult worms produce minimal tissue reaction, but can cause obstruction leading to lymphedema (peau d’orange skin: mimics malignancy)
• Degenerating/dying worms provoke an inflammatory reaction forming a mass with eosinophilic and granulomatous inflammation
• Some of the inflammation is in response to antigens of the endosymbiotic bacteria Wolbachia, which the filarial worms contain
• Secondary lymphangitis and fibrosis may result
• Chronic inflammation leads to nonpitting edema, hyperpigmentation and hyperkeratosis, and possibly superimposed bacterial infection
• Adult filiaria mate and release microfilaria into the blood

Etiology
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• Infection is transmitted by mosquito vectors; humans are definitive hosts (CDC - Lymphatic Filariasis)

Clinical features
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• Unilateral, soft, non-tender swelling, commonly in upper outer quadrant
• May be mobile from quadrant to quadrant and mimic fibroadenoma
• May be associated with enlarged lymph nodes and simulate breast carcinoma
• Overlying skin has induration, hyperpigmentation, dilated veins

Diagnosis
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• Peripheral smear examination for microfilaria
• Excision biopsy

Laboratory
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• Serological testing
• Elevated eosinophils and serum IgG4

Radiology
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• Real time ultrasound may show movement of filarial worms ("filarial dance")
• See Clinical images

Case reports
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• 35 year old man with filariasis presenting as gynecomastia (Breast J 2012;18:83)
• 59 year old woman (Indian J Pathol Microbiol 2008;51:85)
• 69 year old woman (Radiology 2002;222:515)
• 2 adult women with dirofilariasis of breast (Diagn Cytopathol 2002;26:22)
• Woman with filariasis of the breast three years after visiting India (Arch Pathol Lab Med 1987;111:757)

Treatment
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• Diethylcarbamazine to kill microfilaria
• Surgical treatment may be an option for genital and breast disease

Clinical images
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Groups of fine linear calcification

 

Spiral and rod shaped calcification

Ill defined lump

Micro description
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• Cross section of adult worm with surrounding chronic, eosinophilic and granulomatous inflammation, fibrosis

Micro images
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Gravid female worm of
Wucheria bancrofti
surrounded by fibrosis (AFIP)

Transverse section of adult filarial
worm with granuloma

Filarial nematode in
spermatic cord

Cytology description
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• Fragments of adult worms, gravid female worms, microfilariae, macrophages, variable epithelioid granulomas, other acute or chronic inflammatory cells (Diagn Cytopathol 2011;39:8)

Cytology images
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Thyroid

 

Blood smears

Differential diagnosis (clinical)
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• Carcinoma, Fibroadenoma

Additional references
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• CDC - Parasites - Lymphatic Filariasis, eMedicine - Filariasis

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