Unusual huge intramuscular granuloma with calcium phosphate crystal deposition in the buttock

An unusual case of a huge granuloma featuring marked calcium phosphate crystal deposition in muscle is presented. A 58-year-old male demonstrated a well-circumscribed, large, elastic firm mass which had slowly grown over 8 years in the left buttock. Clinical examinations including X-ray, ultrasonography and computed tomography all suggested a neoplastic growth. Surgical excision revealed three inter-connected irregular-shaped masses, measuring up to 11 x 10 x 6 cm in size. The histological appearance was of granulomas composed of numerous small crystals surrounded by reactive mononuclear cells embedded in fibrous tissue containing many foreign body type giant cells. Chemical analysis demonstrated the crystals to be made up of calcium phosphate.