A 49-year-old asymptomatic woman underwent routine screening mammography. This revealed an abnormality in the left breast and further investigations were advised.
The screening mammogram (Fig. 1) revealed a 10mm round mass in the upper-outer quadrant of the left breast (anterior-third) with obscured posterior margins—BIRADS 0. No calcifications, spiculated mass or significant axillary lymph nodes were noted. She was recalled for further clinical assessment, which revealed a palpable lump in the area of concern on mammography, and an ultrasound (US) was advised. Breast US (Fig. 2), in the area of mammographic abnormality, revealed a 12x10 mm thick-walled cyst with a 2 mm polypoidal lesion (without internal vascularity) arising from its non-dependant wall—BIRADS 4a. No other focal abnormality was seen in the rest of the left breast. Ultrasound-guided biopsy of the complex cyst was performed (Fig. 3) without complications. Histopathology (Fig. 4) revealed larva of the cysticercal parasite with surrounding giant cell reaction. Clinical follow-up after a two-month course of albendazole showed no abnormality on palpation or imaging (Fig. 5).
Cysticercosis, which is caused by Taenia solium larvae, is a common parasitic infection of the soft tissues . Humans become occasional hosts by eating undercooked vegetables or pork contaminated by eggs of T. solium or regurgitation of eggs into the stomach from intestines of people harbouring a gravid worm. This parasitic infestation is endemic in Asia, Latin America and Central & South Africa . It can affect multiple organs like brain, spinal cord, orbit, muscles, subcutaneous tissue, breast and heart.
Clinical features depend upon the location of the cyst, number of cysts and host response  and a history of residence or travel in endemic regions may provide a diagnostic clue. Among soft tissue infestations, subcutaneous lesions may present as painless or painful subcutaneous nodules and intramuscular cysts as myalgia, mass, pseudotumour or pseudohypertrophy. In the breast, an uncommon location of affliction [4-7], they can manifest in the form of a lump (painful or painless) making the clinical diagnosis a myriad of possibilities ranging from cysts (simple, complex or complicated), abscess, fibroadenoma or malignancies, to name just a few. Radiological investigations are necessary for characterisation, defining complications such as cyst rupture or associated abscess formation and image-guided biopsies. Mammogram can reveal masses, lymphadenopathy or even calcified worm-like density . The characteristic finding on an US is of a complex cyst with an echogenic focus along the wall, which represents the scolex. In chronic cases, these lesions tend to calcify. Magnetic resonance Imaging has a role when the parasite is viable, where peripheral enhancement of the cyst wall can be demonstrated. Definitive diagnosis is made by tissue sampling, which reveals presence of a scolex and surrounding host response in the form of inflammatory cell infiltration with histiocytes and epitheloid cell granulomas .
Treatment of uncomplicated breast cysticercosis entails a course of anti-helminthic medication and follow-up imaging to look for resolution. If complicated with abscess formation, drainage procedures might be necessary.
Differential Diagnosis List
Fat necrosis or oil cyst
Mastitis or breast abscess