Multicentric reticulohistiocytosis with oral and laryngeal involvement in association with autoimmune/inflammatory syndrome induced by adjuvants (ASIA): expanding the spectrum of two uncommon entities.

Multicentric reticulohistiocytosis (MRH) is the most frequent entity in the group of reticulohistiocytoses. It is usually accompanied by a symmetrical erosive polyarthritis and is frequently associated with cancer and autoimmune disorders. Autoimmune syndrome induced by adjuvants (ASIA) is an inflammatory syndrome triggered by adjuvants such as those contained in vaccines or by silicone implants. Here we report a 71-years old female with a history of breast cancer treated with surgery and subsequent prosthesis who developed a systemic hyperinflammatory syndrome including seronegative symmetric polyarthritis, multiple skin lesions and two large nodular lesions in the oral cavity and larynx. Clinical picture was consistent with a clinical diagnosis of ASIA, with breast implant rupture and/or vaccination against SARS-CoV-2 as possible triggers. Histopathology of skin, oral and laryngeal nodules revealed cutaneous/mucous and submucosal infiltration of large epithelioid mononuclear or binucleated cells with fine granular ground glass-like cytoplasm and round to kidney-shaped nuclei with prominent nucleoli, without atypical features or relevant pleomorphism, accompanied by sparse giant cells and lymphocytes. These cells stained positive for CD68 and CD45 and negative for S100, CD1a, and markers of epithelial or neural/melanocytic differentiation, altogether consistent with a diagnosis of reticulohistiocytosis. Clinic-pathological correlation allowed the final diagnosis of MRH. To our knowledge, this is the first report of a co-occurrence of MRH with ASIA and this is relevant to broaden the spectrum of those both rare diseases.