Calcinosis Circumscripta with Iron Mineralization in an African Green Monkey (Chlorocebus aethiops sabaeus)
A 19-y-old, colony-born, female African green monkey (Chlorocebus sabaeus) presented for recurrent swelling measuring 11 × 5 × 4 cm on the right thigh, around the stifle, which started 5 y previous, resulting in lameness. The affected area had alopecia and crusting and felt lobulated on palpation. Radiographic evaluation revealed multiple foci of well-circumscribed, soft-tissue mineralization within the subcutis and underlying muscles. The monkey was euthanized due to poor quality of life. Postmortem exam demonstrated a yellow-to-red, friable, crepitant, nonencapsulated multilobulated mass, infiltrating skeletal muscles of the right thigh and containing multiple white hard spicules. Microscopic examination revealed abundant irregular-to-globoid amphophilic material (mineralization) in the subcutis and skeletal muscle. The mineralization was surrounded by extensive fibrous connective tissue (fibrosis), lymphocytes, macrophages, and multinucleated giant cells. Histochemical staining, scanning electron microscopy, and infrared spectroscopy determined the mineral material to be composed of calcium phosphate and small amounts of collocated iron. The findings were most consistent with a diagnosis of calcinosis circumscripta (sometimes referred to as tumoral calcinosis). Calcinosis circumscripta in African green monkeys has not previously been reported, although this condition has been reported in rhesus macaques, a common marmoset, and a cynomolgus macaque. The cause of iron mineralization in this case was unknown, and its occurrence within calcinosis lesions has not been previously documented.
A 19-y-old African green monkey with a mineralized mass on the right thigh. (A) Moderate alopecia and crusting on the surface of the mass, firm and lobulated on palpation. (B) Infiltrating and replacing the subcutis and skeletal muscles of the right thigh was a 11 × 5 × 4-cm firm, nonencapsulated, yellow to red, multilobulated mass (skin removed).
(A) Ventrodorsal and (B) right lateral view radiographs of a 19-y-old African green monkey with right hindleg lameness and a chronic swelling on the right hip, revealing the multilocular opacity within soft tissues around the latero-caudal hip and stifle.
Mineralized mass in the red thigh, from an 19-y-old African green monkey. (A) Numerous globoid amphophilic material focally and extensively expanding the soft tissue of the right thigh, stained with hematoxylin and eosin (H&E). On a background of fibrosis, there is moderate mixed inflammatory cell infiltrate (mainly lymphocytes and macrophages). Inset: a blood vessel with thickened tunica media (H&E). (B) Islands and lakes of globoid material staining positive for von Kossa, suggestive of calcification/mineralization. (C) In many areas, the mineralization was also stained positively with Perl Prussian blue stain, consistent with iron deposit. (D) Globoid material was surrounded by extensive fibrous connective tissue (fibrosis) and a multilayered granulomatous inflammation (Masson trichrome stain). Inset: less than 10% of the globoid material positively stained by periodic acid-Schiff stain.
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