Localised primary amyloidosis of inguinal lymph node with superimposed bone metaplasia.

We present here a case of localised primary amyloidosis of the right inguinal lymph node in a 42 year old female. On gross examination the specimen was 4.0 x 4.0 x 3.2 cm in size with a tan-pink color and two whitish-yellow areas of hard consistency. Histologically the lymph node was replaced by an eosinophilic amorphous material, alkaline Congo red, crystal violet, thioflavine T and sodium sulphate-alcian blue (SAB). We observed areas of mature bone metaplasia alternating with sheets of plasma cells and clusters of foreign body giant cell reaction. Immunohistochemical study showed anti-lambda chain staining within the amorphous material. The negative clinical history, physical examination, normal serum electrophoresis and bone marrow and rectal biopsy allowed us to make the diagnosis of localised primary amyloidosis of lymph node. The patient is alive and without evidence of disease progression to systemic amyloidosis or plasma cell dyscrasia, after clinical follow-up of seven years.