Mixed lobular and ductal carcinoma in situ is very rare. We recently experienced a case of invasive lobular carcinoma associated with mixed lobular and ductal carcinoma in situ in a 50-year-old female. The infiltrating portions of lobular carcinoma revealed thread-like strands of tumor cells. Lobular carcinoma in situ with pagetoid spread into the ducts and ductal carcinoma in situ of the predominantly papillary type were also noted in the same mass.
Metastasis to the breast from medullary carcinoma of the thyroid is extremely rare. We report a case of metastatic medullary carcinoma of the thyroid which presented as multiple breast masses with ipsilateral axillary lymphadenopathy in a 48-year-old woman. Six years ago, she underwent total thyroidectomy and neck dissection because of palpable neck masses, with a diagnosis of medullary thyroid carcinoma. Histological features of breast masses showed single- file or linear-cord arrangements, with plasmacytoid appearance, and the initial diagnosis was invasive lobular carcinoma. She underwent modified radical mastectomy. The tumor cells were diffusely positive for E-cadherin, calcitonin and thyroid transcription factor-1 (TTF-1) and were metastatic medullary carcinoma of thyroid. In the patients with a history of medullary carcinoma of the thyroid, a careful examination is necessary for a breast mass composed of solid and cord-like clusters of small round to ovoid cells with plasmacytoid appearance.
Immunohistochemical staining for E-cadherin, calcitonin and TTF-1 could be helpful for differential diagnosis.