Hydatid cyst: unusual presentation as 'breast lump'.

Hydatid cyst in the breast is rare. We report a case of hydatid cyst in the breast in a 30-year-old Indian rural woman who presented with a lump in her left breast. MRI findings showed a cystic lesion in the breast. Histopathological examination showed features consistent with hydatid cyst with surrounding adherent pericystic breast tissue showing fibrocollagenisation and inflammatory response. ELISA for echinococcal antigen was also found to be positive. This case emphasises that preoperative diagnosis of hydatid cyst in the breast is difficult and often missed as the breast is a rare site of echinococcal infection and clinical and imaging findings are wide and non-specific. Cytological diagnosis by fine-needle aspiration may not always be possible. Therefore, hydatid cyst in the breast should always be considered in the differential diagnosis of a breast lump and histopathological confirmation is necessary for early and appropriate treatment.