Spontaneous regression of primary extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) colliding with invasive ductal carcinoma of the breast: a case report

Malignant lymphomas of the breast, whether they are primary or secondary, are rare diseases, constituting only around 0.1 to 0.15% of the primary neoplasm of the breast. Although the most prevalent histological subtype is diffuse large B-cell lymphoma, primary extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) also occurs in the breast as in other extranodal sites, comprising about 15% of malignant lymphomas of the breast. In many cases, primary MALT lymphoma of the breast is low grade lymphoma, localized in the breast with indolent behavior and good prognosis. Here we report a case of spontaneous regression of primary MALT lymphoma of the breast. The lymphoma collided with invasive ductal carcinoma in the breast. Both tumors were identified in the Vacora biopsy specimen before the operation. However, the lymphoma disappeared, while the carcinoma remained, in the resected mass. To our knowledge, this is the first case report of spontaneous regression of MALT lymphoma of the breast colliding with breast cancer.