ALK-Positive Inflammatory Myofibroblastic Tumor of the Nipple During Pregnancy-An Unusual Presentation of a Rare Disease.

Inflammatory myofibroblastic tumors (IMT) is a benign to low-grade malignant neoplasm most commonly occurring in the viscera and soft tissues of children and young adults. Involvement of the breast is very rare. This report presents the first case of IMT of the nipple and highlights the histologic features and differential diagnosis at this unusual anatomical site. The patient was a 31-years-old pregnant woman with a palpable mass at the upper half of the left nipple. The lesion appeared after breastfeeding of her first child and increased in size during her second pregnancy. A conservative, incomplete surgical excision was performed in the 24th week of the second pregnancy. The residual tumor subsequently underwent spontaneous regression. There was no evidence of disease 5 years after surgery. FISH and immunohistochemical analyses revealed rearrangement and overexpression of the ALK gene, a typical feature of both pulmonary and extrapulmonary IMT.