Extraskeletal osteosarcoma and its histological mimics

Extraskeletal osteosarcoma infiltrating pancreas, spleen, gastric, and left kidney: a case report

“…Some other tumor-like lesions mimic ESOS, such as osteosarcoma with tumoral osteoid production, reactive metaplastic bone, dense collagen-mimicking osteoid, or even a benign soft tissue tumor with bone formation. Especially in this case, where the tumor was located at the retroperitoneal, dedifferentiated liposarcoma is a more prevalent entity possibly happening [ 10 ]. All specimens were sent for histological examination, which revealed high-grade, pleomorphic, vesicular, chromatin tumor cells with spindle nuclei and involvement of cartilage and osteoid matrix that forms a lace-like pattern.…”

“…These findings suggest osteosarcoma as the diagnosis. The scarcity of ESOS results in diagnostic difficulties owing to radiological and pathological similarities with other conditions, which are more common [ 10 ]. Making a correct diagnosis of ESOS is vital because it needs a more aggressive treatment strategy than other sarcomas [ 11 ].…”

A staghorn kidney stone or extraskeletal osteosarcoma of the kidney? A case report and literature review

“…9 Differential diagnoses of extraskeletal sarcoma include other sarcomas that produce tumoral osteoid or bone, such as dedifferentiated liposarcoma, leiomyosarcoma, and solitary fibrous tumor, as well as sarcomas that contain reactive metaplastic bone, such as synovial sarcoma and sarcomas with dense collagen that mimics osteoid, such as spindle cell/sclerosing rhabdomyosarcoma, and also benign soft tissue lesions such as phosphaturic mesenchymal tumors. 10 Because the prognoses of ESOS and these mimic lesions differ significantly, accurate diagnosis with proper sampling technique, preparation, and adequate volume of biopsied specimens is essential.…”

“…The specimen should be positive for mesenchymal markers, vimentin (VIM) and S-adenosylmethionine (SAM) and negative for epithelial markers, RCC and CK. 10 Enbloc resection with negative margin is a positive prognostic factor and the only treatment that can be curative. Resection margin, size of primary tumor, and depth of invasion are other prognostic factors for ESOS.…”

“…The specimen should be positive for mesenchymal markers, vimentin (VIM) and S-adenosylmethionine (SAM) and negative for epithelial markers, RCC and CK. 10 …”