Anaplastic lymphoma kinase-positive inflammatory myofibroblastic tumor of the breast: a case report and review of the literature.

Background: Few reports of inflammatory myofibroblastic tumor (IMT) of the breast have been published worldwide. Furthermore, primary anaplastic lymphoma kinase (ALK)-positive IMT of the breast is extremely rare. To date, only six patients with ALK-positive IMT have been reported in the literature.

Case Presentation: A 52-year-old woman underwent a medical examination, and a left breast mass was detected. She did not feel a mass in her chest. Mammography showed a focal asymmetric density at the lower outer portion of the left breast. Breast ultrasonography showed a 1.2-cm hypoechoic lesion with relatively clear boundaries and poor blood flow. Magnetic resonance imaging and computed tomography revealed a solitary heterogeneous mass in the left breast. Pathologic examination revealed a fibrosing lesion with proliferation of fibroblastic cells arranged in a storiform pattern and admixed inflammatory cells. Immunohistochemical examination showed that the tumor cells were positive for ALK. Under the preoperative diagnosis of IMT, we performed partial mastectomy with adequate margins. The postoperative diagnosis was pathologically confirmed as IMT. Immunohistochemical staining also showed overexpression of ALK-1 in the tumor. The patient had a good clinical course for 24 months postoperatively, without recurrence or metastasis.

Conclusions: IMT of the breast shows nonspecific imaging findings, making preoperative diagnosis difficult. Nevertheless, IMT has the characteristics of low-grade neoplasms with recurrence, invasion, and metastatic potential. Our report emphasizes the importance of determining a treatment plan as soon as possible based on an accurate diagnosis to improve the prognosis of this disease.