Amyloidoma is a localized tumoral deposition of amyloid protein without systemic involvement. Though rare, it has been reported in various tissues. Calcified amyloidoma is an extremely uncommon condition that can mimic benign and malignant soft tissue tumors. Here, we report a case of isolated calcified amyloidoma, which clinically simulated a soft tissue sarcoma.
A 60-year-old previously healthy female presented with a slow growing hard mass in her left lower abdomen. She denied any pain, weight loss, B symptoms, history of surgery or significant trauma. Imaging studies confirmed the presence of a heterogeneous mass within the abdominal muscles. With the clinical suspicion of sarcoma, a core biopsy was obtained which showed focal necrosis and granulomatous reaction. The mass was surgically excised. Histopathological evaluation revealed the concentric deposition of dense amorphous eosinophilic material associated with metaplastic bone formation, lymphoplasmacytic infiltrate and multinucleated giant cells. The eosinophilic deposit showed strong reactivity with Congo red stain and displayed typical apple-green birefringence under polarized light confirming amyloid. Normal serum protein electrophoresis and hematological studies ruled out an underlying systemic plasma cell dyscrasia.
Primary localized amyloidoma should be considered in the differential diagnosis of soft tissue masses even in the absence of systemic amyloid disease.
(C) 2014 Royal College of Pathologists of Australasia