First case report of ruptured giant expanding breast oil cyst

Fat necrosis is a common sequelae of breast trauma. Its many presentations have been described in the literature. Oil cyst is one of the less common presentations of fat necrosis. Giant oil cyst is rare and may take many years to mature in an unstable environment of the women's breast. To our best knowledge, rupture of a giant oil cyst has never been reported. Yet, it should be included on the list of differential diagnoses along with hematoma, infection, or neoplasm. When a patient presents with an expanding breast lump, clinicians should be aware of the potential for oil cyst rupture and its features.

A 51-year-old woman presented to a breast clinic with concern of an expanding painless left breast lump for the last 4 months. The lump first appeared 12 years ago shortly after a car accident and was stable for many years. The initial left breast ultrasound was inconclusive, but diagnostic mammogram revealed a giant ruptured calcified oil cyst. Due to the availability of prior diagnostic images, we were able to retrospectively follow the unique sequelae of fat necrosis from the development of giant oil cyst shortly after the breast trauma and up to the final outcome of ruptured calcified oil cyst.

Trauma to a woman's breast can lead to the formation of a large oil cyst which can remain present for years, peripherally calcify, and is susceptible to rupture. Clinicians should be aware of this potential complication when presented with the case of expanding breast lump. Diagnostic mammogram is a study of choice and demonstrates benign pathognomonic features of an oil cyst.