PMC6604449_01
Initial radiography of Lesions. a Plain film radiography showing the lytic lesions present in the right distal clavicle and humeral head (arrows). b T1 MRI of the chest showing the T9 pathologic fracture (arrow)
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Fig1
Radiographs showed multiple lytic lesions (Fig. 1a), and subsequent computed tomograms (CT) revealed extensive lytic lesions to bilateral humeral heads, iliac bones, ischial bones, thoracic spine and lumbar spine with pathologic fracture of T9. Due to new-onset numbness and tingling of her leg, emergent magnetic resonance image (MRI) was obtained which confirmed extensive metastases to the left femur with distal non-displaced diaphysis pathologic fracture, in addition to metastases to the humerus, scapula, clavicle, 4th and 5th ribs, throughout the pelvis, and the spine with pathologic T9 fracture and mild spinal canal stenosis but no cord compression (Fig. 1b).
Staining of Specimens. Histopathologic features of the T9 biopsy and intraoperative femur stabilization specimens, indicated in lower right corners. A Nests of osteoid producing cells can be seen surrounded by swirls of pleomorphic spindle cells and reticular substance. HE x40. B The tumor is predominantly made up of irregular spindle cells. HE x40. C The tumor can be seen infiltrating normal bone architecture, HE x40. D Pleomorphic spindle cells with intervening stroma. HE x200. E Poorly defended clusters of cells can be seen surrounded by neoplastic stroma, HE x200. F Spindle cells showing a high degree of pleomorphism, hyperchromatic nuclei, and irregular nuclear contours. HE x200. G Positive immunohistochemical staining for OSCAR cytokeratin in scattered spindle cells, x200. H Scattered positive immunohistochemical staining for OSCAR cytokeratin, x200. I The same scattered positive immunohistochemical staining for OSCAR cytokeratin is seen in the femur biopsy, x200
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Fig2
Histopathologic examination of a biopsy from the T9 lesion revealed proliferation of spindle cells with hyperchromatic, pleomorphic nuclei, and irregular nuclear contours organized in swirls giving a nested appearance (Fig. 2A, B, D, E). Focal areas of osteoid production and large amounts of reticular substance production can be seen (Fig. 2A, D). However, immunohistochemical staining showed the atypical spindle cells to have scattered staining for OSCAR cytokeratin, with weakly and patchy positivity for pankeratin, hallmarks of an epithelial origin (Fig. 2G, H). Histopathologic examination of the intraoperative femur biopsy showed a similar cytomorphologic profile to the T9 biopsy (Fig. 2C, F, I). Additional stains performed on this section showed the neoplastic cells to be positive for OSCAR (Fig. 2I) and negative for CD99 and EMA, further ruling out epithelioid sarcoma, synovial sarcoma, and mesenchymal chondrosarcoma.
Additional immunostaining of specimens. Immunohistochemical features of the T9 biopsy and intraoperative femur stabilization specimens indicated at left, all x200. Pankeratin is weakly positive in a subset of spindle cells; CK7, GATA, SOX10, and S100 all showed no reactivity in the T9 biopsy specimen. Additional stains performed on the specimen from the femur stabilization are non-reactive for CD99, AE-1/AE-3, EMA, CD45, and CD138
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Fig3
Radiographic PET/CT staging of lesions. The delayed enhancement PET scan shows 18-fluorodeoxyglucose (FDG) uptake over time. Metabolically active organs such as the bladder, kidneys, testicles and brain show increased uptake normally. a Initial staging PET/CT showing lesions in the bilateral humeri, claviculi, distal femurs, proximal tibias, pelvis, and spine. b 6-month re-staging PET/CT showing regression of lesions in bilateral femurs, right shoulder, and multiple levels of the thoracic spine consistent with a chemotherapeutic response. c 9-month re-staging PET/CT showing multifocal progression of osseous lesions
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Fig4
Whole body positron emission tomography CT (PET/CT) showed extensive hypermetabolic metastasis to the bony skeleton (Fig. 4a), however a non-osseous primary was never identified despite thorough clinical and radiologic evaluation.  At 6-month follow-up, she had completed four cycles of chemotherapy and showed a positive treatment response with decreased hypermetabolism of bony lesions (Fig. 4a, b). However, at 9 months follow up following six cycles, PET/CT showed progression of the lesions, with multifocal areas of increased metabolic activity throughout the spine, sacrum, and pelvis (Fig. 4b, c).