title: Extensive Regional Metastasis of High-Grade Mucoepidermoid Carcinoma of an Unknown Primary Tumor.
abstract: OBJECTIVE
  Mucoepidermoid carcinoma (MEC) is the most common salivary carcinoma. It arises most frequently in the major salivary glands, but can also arise in minor glands or intraosseous sites. MEC of an unknown primary occurs very rarely. The present report documents only the third case reported in medical studies.
  
  
  METHODS
  A 66-year-old man with previous carcinoma in situ (CIS) of the left posterior oral tongue that had been excised in 2004 and again in 2010 presented with a hard lymph node, 3 × 2 cm at level II of the right neck in July 2015. Positron emission tomography-computed tomography (PET-CT) revealed multiple, bilateral cervical lymphadenopathy, with no primary site identified. Fine needle aspiration biopsy and cytologic examination from the right neck was positive for malignancy, suggestive of metastatic squamous cell carcinoma. Panendoscopy and biopsy revealed CIS at the tongue bases and tonsils bilaterally (p16-negative). The patient's case was presented to a tumor board, and definitive concurrent cispl.atin-based chemoradiation was recommended for TisN2cM0, stage IVA oropharyngeal CIS, which was completed in November 2015. PET-CT in January 2015 showed complex interval changes, with some areas demonstrating improvement (ie, no uptake in the left neck) and worsening in others (ie, increased metabolic activity in the right neck), suggestive of residual disease. Repeat PET-CT in March 2016 showed increased nodal involvement and increasing standardized uptake value. Bilateral modified radical neck dissection was undertaken, and histologic examination showed high-grade MEC in 51 of 61 lymph nodes with extracapsular spread and soft tissue involvement.
  
  
  RESULTS
  The patient died in May 2016 at 2 months after surgery.
  
  
  CONCLUSIONS
  Metastatic MEC of an unknown primary is a diagnostic challenge. PET-CT might not be the most reliable diagnostic investigation to identify the primary or metastatic foci, such as was demonstrated in the present case.
authors.affiliation: Fellow, Department of Oncology/Microvascular Surgery, University of Maryland Medical Center, Baltimore, MD. Electronic address: naseemghazali@doctors.org.uk.
authors.forename: Naseem
authors.initials: N
authors.lastname: Ghazali
authors.affiliation: Dental Undergraduate, University of Maryland School of Dentistry, Baltimore, MD.
authors.forename: Alyssa
authors.initials: A
authors.lastname: Flashburg
authors.affiliation: Chairman and Professor, Department of Oral and Maxillofacial Surgery, University of Maryland School of Dentistry, University of Maryland Medical Center, Baltimore, MD.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Ord
mesh_terms: D000368:Aged; D018277:Carcinoma, Mucoepidermoid / Q000175:diagnosis / Q000556:secondary / Q000601:surgery; D003937:Diagnosis, Differential; D003952:Diagnostic Imaging; D017809:Fatal Outcome; D006801:Humans; D008207:Lymphatic Metastasis; D008297:Male; D037981:Neck Dissection; D060787:Neoplasm Grading; D009382:Neoplasms, Unknown Primary / Q000473:pathology*; D009959:Oropharyngeal Neoplasms / Q000175:diagnosis / Q000556:secondary / Q000601:surgery