[87] 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.

Table1: Clinicopathological characteristics of metastatic NSCLC to breast
Age/genderLung ca known at time of breast bxBreast mass multifocalityDCISERTTF1Axillary LNsDistant metastases
64/FYsolitaryN--+Y
70/FNtwoN+++NA
72/FNsolitaryN-++Y
76/MNtwoN---Y
63/FNtwo, bilateralN-++Y
45/FYsolitaryN-+-Y
70/FYsolitaryN-NA-Y
69/FNsolitaryN-++Y
77/FYsolitaryN--NAY
65/FNsolitaryNNA+-Y
55/FYmultiple bilateralN-+-Y
Y=yes; N=no; NA=not available


Conclusions: Although rare, ACL can masquerade as PBC and needs to be considered in the differential diagnosis because the treatment and prognosis differ significantly. Even in the absence of a clinical history of lung carcinoma, metastatic carcinoma to the breast should be considered in at least one of the following scenarios: (1)single or multiple well circumscribed lesions of the breast with distant metastases but negative axillary lymph nodes, (2)cases which lack an in situ component and are triple negative yet not poorly differentiated or (3)those presenting as stage 4 PBT and/or having an unusually aggressive clinical course on standard breast therapy.
Category: Breast

Monday, March 19, 2012 1:00 PM

Poster Session II # 41, Monday Afternoon

 

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