Metastatic Renal-Cell Carcinoma of the Oro-Facial Tissues: A Comprehensive Review of the Literature with a Focus on Clinico–Pathological Findings

Background Metastatic tumors of the oro-facial tissuesare rare, with an incidence ranging between 1% and 8% of all oral malignant tumors. Generally reported with a peak of incidence in the 5–7th decades but possibly occurring at any age, metastases may represent the first sign of an occult cancer or manifest in patients with an already known history of a primary carcinoma, mostly from the lungs, kidney, prostate, and colon/rectum in males, and the uterus, breast, lung, and ovary in females. In the oro-facial tissues, the most involved sites are the oral mucosa, gingiva/jawbones, tongue, and salivary glands. Methods A broad and deep literature review with a comprehensive analysis of the existing research on oro-facial metastases from renal-cell carcinoma (RCC) was conducted by searching the most used databases, with attention also paid to the clear-cell histological variant, which is the most frequent one. Results Among the 156 analyzed studies, 206 cases of oro-facial metastases of renal cancer were found in patients with an average age of 60.9 years (145 males, 70.3%; 61 females, 29.6%). In almost 40% of the cases, metastasis represented the first clinical manifestation of the primary tumor, and 122 were histologically diagnosed as clear-cell renal-cell carcinoma (ccRCC) (59.2%). The tongue was involved in most of the cases (55 cases, 26.7%), followed by the gingiva (39 cases, 18.9%), mandible (35 cases, 16.9%), maxilla (23 cases, 11.1%), parotid gland (22 cases, 10.6%), buccal mucosa (11 cases, 5.3%), lips (7 cases, 3.3%), hard palate (6 cases, 2.8%), soft palate, masticatory space, and submandibular gland (2 cases, 0.9%), and lymph nodes, tonsils, and floor of the mouth (1 case, 0.4%). Among the 122 ccRCCs (84 males, 68.8%; 38 females, 31.1%), with an average age of 60.8 years and representing in 33.6% the first clinical manifestation, the tongue remained the most frequent site (31 cases, 25.4%), followed by the gingiva (21 cases, 17.2%), parotid gland (16 cases, 13.1%), mandibular bone (15 cases, 12.2%), maxillary bone (14 cases, 11.4%), buccal mucosa and lips (6 cases, 4.9%), hard palate (5 cases, 4%), submandibular gland and soft palate (2 cases, 1.6%), and lymph nodes, tonsils, oral floor, and masticatory space (1 case, 0.8%). The clinical presentation in soft tissues was mainly represented by a fast-growing exophytic mass, sometimes accompanied by pain, while in bone, it generally presented as radiolucent lesions with ill-defined borders and cortical erosion. Conclusions The current comprehensive review collected data from the literature about the incidence, site of occurrence, age, sex, and survival of patients affected by oro-facial metastases from renal-cell carcinoma, with particular attention paid to the cases diagnosed as metastases from clear-cell renal-cell carcinoma, which is the most frequent histological variant. Clinical differential diagnosis is widely discussed to provide clinicians with all the useful information for an early diagnosis despite the effective difficulties in recognizing such rare and easily misdiagnosed lesionsTheir early identification represents a diagnostic challenge, especially when the clinical work-up is limited to the cervico–facial region. Nevertheless, early diagnosis and recently introduced adjuvant therapies may represent the key to better outcomes in such patients. Therefore, general guidelines about the clinical and radiological identification of oro-facial potentially malignant lesions should be part of the cultural background of any dentist.