Clinicopathological characteristics and treatment outcomes of occult breast cancer: a SEER population-based study

Abstract

BackgroundOccult breast cancer (OBC) is a rare type of breast cancer that has not been well studied. The clinicopathological characteristics and treatment recommendations for OBC are based on a limited number of retrospective studies and thus remain controversial.Patients and methodsWe identified 479 OBC patients and 115,739 non-OBC patients from 2004 to 2014 in and the Surveillance, Epidemiology, and End Results (SEER) database. The clinicopathological characteristics and survival outcomes were compared between OBC and non-OBC patients. We used the propensity score 1:1 matching analysis to evaluate OBC vs non-OBC comparison using balanced groups with respect to the observed covariates. We further divided the OBC population into four groups based on different treatment strategies. Univariable and multivariable analyses were used to calculate and compare the four treatment outcomes within the OBC population.ResultsOBC patients were older, exhibited a more advanced stage, a higher rate of negative estrogen receptor and progesterone receptor status, a higher rate of HER2-positive status, and a higher rate of ≥10 positive lymph nodes, and were less likely to undergo surgical treatment than non-OBC patients. After adjustments for clinicopathological factors, the OBC patients exhibited a significantly better survival than the non-OBC patients (P<0.001). This result was confirmed in a 1:1 matched case–control analysis. Within the four OBC treatment groups, we observed no difference in survival among the mastectomy group, the breast-conserving surgery (BCS) group, and the axillary lymph node dissection (ALND)-only group. The multivariable analysis revealed that the sentinel lymph node dissection-only group had the worst prognosis (P<0.001). Conclusion: OBC has unique clinicopathological characteristics and a favorable prognosis compared with non-OBC. BCS plus ALND and radiotherapy showed a survival benefit that was similar to that of mastectomy for OBC patients.

Unique presentation of occult breast cancer with uterine cervix metastasis

“…2 Most patients were 50 years or older in age and presented with advanced stage cancers that were more likely than non-OBC to be ER-and PR-negative. 2 To our knowledge, this is the first reported case of OBC metastatic to the uterine cervix. The uterine cervix is, in fact, very rarely involved even in metastatic non-OBC, having been reported in anywhere from 0.8% to 1.7% of patients.…”

“…Occult breast cancers are rare entities. Only 0.4% of the 116 218 subjects listed in the Surveillance, Epidemiology and End Results database for the 2004‐2014 timeframe were diagnosed with OBC . Most patients were 50 years or older in age and presented with advanced stage cancers that were more likely than non‐OBC to be ER‐ and PR‐negative …”

“… Unfavorable outcomes, however, were more likely to occur with tumors that were ER‐positive and when 10 or more lymph nodes were involved. Yet, after adjusting for confounders, OBC patients have been shown to have better overall survival (OS) than non‐OBC patients ( P < .001) …”

“…In women in the United States, breast cancer represents the most common malignancy and the second leading cause of cancer‐related deaths . OBC, however, is relatively rare . It is characterized by metastatic disease confirmed histologically as primary breast cancer, in the absence of a tumor mass on clinical examination and mammography .…”

“…OBC often presents with nonspecific symptoms, owing to lack of disease in the breast, which can make diagnosis challenging . When discovered, it is usually metastatic to the axillary lymph nodes . Although less commonly reported, other metastatic sites include bone, liver, lymphatic system, skin, orbits, bone marrow, lung, and spleen .…”