This observation represents an unusual clinical aspect of a rare breast cancer, mucinous carcinoma which represents 1% of all breast cancers, with its two pure and mixed forms whose treatment and prognosis are not identical.
The pure form has a good prognosis despite the exceptional clinical presentation of this type of breast cancer hence the interest of this case study, Mrs. L, a 70 year-old without risk factors admitted for mastitis of the left breast with rapid installation over 2 months, suspected of malignancy, yet the couple mammography / ultrasound did not manifest this malignancy, it shows an aspect of opacity well circumscribed of sharp contours.
After the needle biopsy, the diagnosis of mucinous carcinoma was made which determined a suitable management is a neoadjuvant chemotherapy followed by a radical treatment, the hormonotherapy was continued in front of the expression of the hormonal receptors. Post-treatment surveillance did not report distant recurrence or metastasis.