Metastatic Non-Small Cell Lung Carcinoma (NSCLC) Masquerading as Primary Breast Cancer (PBC) – A Rare yet Major Pitfall in Pathologic Diagnosis
Rola Ali, Tareq Mohammad, Malcolm Hayes, Diana Ionescu. BC Cancer Agency, Vancouver, BC, Canada
Background: PBC is the most common malignancy of women but metastatic malignancy to the breast has a reported frequency of 0.4 - 1.3%. The commonest non-mammary tumors (NMT) in the breast are hematological malignancies, malignant melanoma, lung tumors, renal cell carcinoma, ovarian tumors, and thyroid carcinoma. Accurate and timely diagnosis of metastatic NMT in the breast is mandatory to enable proper treatment. We compared clinical and pathological characteristics of metastatic NSCLC to breast with PBC to provide practical tools for pathologists in this essential differential diagnosis.
Design: Cases of non-hematopoietic NMT diagnosed in breast specimens were collected from archives of the BCCA Department of Pathology and the private collection of one author (MH). Clinical charts and pathologic slides were reviewed and ancillary tests performed where appropriate.
Results: 28 cases of metastatic NMT were identified including: 13 lung tumors, 6 melanomas, 4 ovarian tumors, 1 renal cell carcinoma, 1 vulvar carcinoma, 1 thymic carcinoma, 1 gastric carcinoma, and 1 carcinoid. NSCLC was the most common metastasis. Adenocarcinoma of lung (ACL) was most frequent (8/13), followed by small cell carcinoma (2/13). There was one case each of adenosquamous carcinoma, large cell neuroendocrine carcinoma and pulmonary carcinoid. The clinical and pathological features are summarized in table 1.
|Age/gender||Lung ca known at time of breast bx||Breast mass multifocality||DCIS||ER||TTF1||Axillary LNs||Distant metastases|