Cytohistological and Immunohistochemical Correlation of Cutaneous Mixed Tumors: A Series of Four Cases and Review of Recent Molecular Updates

Fine needle aspiration cytology (FNAC) is an established diagnostic modality today, but its utilization in skin tumors is limited by the fact that most of these lesions are small and easily accessible for clinicians to perform an excision biopsy. As a result, our knowledge of the cytological features of some of the uncommonly encountered skin tumors is still lacking. The aim of this study was to correlate the cytological features of cutaneous mixed tumors (CMTs) with histological and immunohistochemical findings in four cases of CMT in commonly and uncommonly encountered locations. We also review the recent updates highlighting the various genetic rearrangements and newer more specific immunohistochemical markers described so far. This was a retrospective study, and all the slides were taken from our departmental archives. Case 1 was a 25-year-old male who presented with a gradually increasing painless swelling over the right angle of the mouth of 1.5 years duration. Case 2 was a 45-year-old male with swelling on the right forearm for the last three years. Case 3 was a 35-year-old female with a forehead swelling of one year duration. Case 4 was a 55-year-old female with left cheek swelling for two years. On clinical examination, all four nodular swellings were predominantly in the skin/subcutaneous tissue. On cytology, all cases showed abundant chondromyxoid material with clusters of benign epithelial cells and a fair number of predominantly singly scattered myoepithelial cells. The diagnosis of all four cases was further confirmed on histopathology and immunohistochemistry, and the findings correlated well with cytology. The cytological features of CMT closely correlate with their histopathological and immunohistochemical features. Newer immunohistochemistry (IHC) marker pleomorphic adenoma gene 1 (PLAG1) may be helpful in making a definitive diagnosis of CMT on cytology and cell block preparation along with a good clinical correlation. Complete surgical excision is the treatment of choice, and recurrence is rare.