Dirofilariasis of Breast Mimicking Malignancy - A Rare Entity

Human dirofilarial infection usually presents as pulmonary coin lesion or as subcutaneous nodule. We report the case of a 60-year-old female presented clinically with swelling in the lower-outer quadrant of the right breast for 2 weeks. Ultrasound reported as atypical lesion suggest fine-needle aspiration cytology (FNAC) correlation and follow-up. Clinical examination - subcutaneous nodule of size 2 cm x 2 cm presents in the lower-outer quadrant. Clinical suspicious of carcinoma was considered and FNAC was done. Aspirated pus-like material and adult worm about 4 cm in length were attached to the needle. Smear was air-dried and stained with Giemsa. Smears were cellular and showed numerous neutrophils, eosinophils, and a few histiocytes in a necrotic background and also noted coiled adult dirofilarial worm. Cellblock was prepared and it showed the cut section of dirofilarial worm with cuticle, muscular layer, intestine, and reproductive tube. We report this case entity due to diagnostic confusion with breast malignancy clinically and radiologically.