Metastatic tumors in oral mucosa and jawbones: Unusual primary origins and unusual oral locations

•Kidney, breast and skin are the most common origins for oral metastases.•These primaries do not coincide with cancer frequency in general population.•Metastases are often unsuspected clinically for malignancy, mimicking reactive lesions.•Oral masses in adults may represent metastases from occult malignancy. To perform clinico-pathological characterization of a large series of oral metastases, collected from 3 main medical centers in Israel and compare findings to data on frequency of primary cancer types in the population. Pathology archives were searched for cases of metastatic tumors to the oral soft tissues and jawbones, 1990 – 2016. Metastases to the skin of face or to major salivary glands have been excluded. Demographic data and histopathological features were analyzed. Study population included 60 patients, 35 females and 25 males (ratio of 1.4:1). The age range was 17–87 years, mean 67.7 + 14.36 years. Only 3 (5%) patients were under 40 years, the remaining clustered predominantly in the 60–80 year age group. The mean age of females (59 + 13.84) was significantly lower than that of males (67.44 + 14) (p = 0.03). There was an almost equal distribution between the oral soft tissue and the jawbones (48.3% and 51.7%, respectively). The five most common organs from which metastases were distributed to the oral cavity and jawbones combined were kidney (20%), breast (15%), cutaneous (predominately melanoma, 13%), lung (11.7%) and soft tissue-sarcomas (8.3%). For comparison, Israel National Cancer Registry 2013 reported that the most frequent malignancies were breast (25.8%), colorectal cancer (16.3%), lung (12%) and prostate (10%). Malignant melanoma was 6th (5.4%), kidney malignancy was only 9th in frequency (4.2%). Although the gingiva and jawbones were the most frequent locations, some cases presented in unusual locations, (mandibular vestibule, lower lip, posterior dorsal tongue), without any specific clinical feature to suggest metastasis. The most frequent primary origins for oral metastasis do not correspond to the relative frequency of the primary tumors in the population, indicating that metastatic spread is not a random process. Although the majority of metastasis involves the gingiva and jawbones, any other oral mucosal location might be involved. Thus, in adult/older patients, metastasis from a distant site should be included in the differential diagnosis of oral masses at any oral location, whether the existence of a primary tumor is reporte