Solitary adult xanthogranuloma in external auditory canal: Cyto-histopathological correlation of an uncommon entity at an uncommon site

Juvenile xanthogranulomas (JXG) are the most common type of self-limiting non-Langerhans cell histiocytosis (LCH) usually presenting in infancy and early childhood. Clinically, they present as solitary to multiple rounded cutaneous nodules which resolve over time. Adult type xanthogranulomas (AXG), though histologically similar to JXG, are usually single and do not regress spontaneously. AXG arising in the external auditory canal (EAC) is a rare occurrence with very few cases reported in literature. We present a case of AXG in a 48-year-old man, arising from the right EAC. This case is unique as it is the only case to be described with both cytology and histology correlation. On cytology, smears showed scattered foamy histiocytes, inflammatory cells and thick stromal fragments. Cytology differential diagnoses of xanthomatous lesion, benign fibrous histiocytoma (BFH) and ceruminous adenoma were given; final diagnosis was deferred to histopathology which confirmed it to be an AXG. Thus, it is important to keep the diagnosis of AXG in mind while dealing with solitary polypoidal lesions in EAC showing prominent foam cell component. Lipidised BFH forms a close differential diagnosis, however can be excluded by subtle points on cytology and on histopathology.