A case of multicentric reticulohistiocytosis with multiple nodules in the oral cavity

Multicentric reticulohistiocytosis (MRH) is a rare systemic disease categorized under non-Langerhans cell histiocytosis. It is clinically characterized by papulonodular skin lesions and multiple destructive arthritis and is often associated with malignant tumors. We report a rare case of MRH involving multiple nodules in the oral cavity. A 77-year-old woman was referred to our department with multiple nodules on her lower lip, buccal mucosa, and tongue, which caused difficulties with mastication. She had a history of knee osteoarthritis and heart failure, for which she was under treatment by her primary physician. Initially diagnosed with multiple benign tumors, she underwent a biopsy, which suggested a granular cell tumor. Consequently, the tumors were excised under general anesthesia. Three days prior to the operation, the patient was referred to the Department of Dermatology for a nodule on the occipital skin, and a biopsy was performed. Histopathological examination of both the skin lesion and the orally excised tumors revealed histiocytes with ground-glass eosinophilic cytoplasm. Immunohistochemical analysis showed that the histiocytes were positive for CD68 and negative for AE1/AE3, S-100, and CD1a. These findings confirmed the diagnosis of MRH. Systemic screening subsequently identified thyroid and breast cancers. Due to her deteriorating condition, no active treatment could be administered, and she passed away 11 months post-operation from heart failure. During this period, new oral tumors emerged, but no recurrence was detected in the previously excised areas.