NCIt definition : An uncommon, mass-forming lesion that affects single or multiple sites. It is characterized
by the presence of a lymphoplasmacytic infiltrate rich in IgG4-positive plasma cells
and storiform tissue fibrosis, and increased serum IgG4 levels. It usually occurs
in the pancreas, submandibular glands, lacrimal glands, lymph nodes, and hepatobiliary
tract. Patients usually present with fatigue and weight loss. It responds to steroids
treatment and follows a course of remissions and recurrences.;