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Mentions: The curetted lesion was resected in sufficiently solid, granular, reddish-brown fragments. Microscopic examination revealed fibrous septa with spindle cell fibroblastic proliferation, capillaries and extensive areas of mature osteoid and reactive woven bone formation rimmed by plump benign-appearing osteoblasts (Figures 3 and 4). The bony trabeculae tended to anastomose. The spindle cells had low mitotic activity, and atypical forms were absent. There were no signs of nuclear atypia, necrosis or other features of malignancy. Multi-nucleated giant cells were patchy in distribution. There were also sparse, small, aneurysmal cystic spaces identified that contained blood and were surrounded by multi-nucleated giant cells (Figure 5). Scattered histocyte-like cells and lymphocytic foci were observed. The histological features were consistent with the solid variant of an ABC.
Solid variant of aneurysmal bone cyst of the heel: a case report
Bottom Line: The eventual diagnosis is based on microscopic evidence and is made when a predominance of solid to cystic elements is found.The present case is of great interest because of the nature of the neoplasm and the extremely unusual location in which it developed.Pathologists must be alert for such a diagnosis.
Affiliation: Department of Pathology, Metaxas Anticancer Hospital, Piraeus, Greece. email@example.com.
Introduction: An aneurysmal bone cyst is a benign but often rapidly expanding osteolytic multi-cystic osseous lesion that occurs as a primary, secondary, intra-osseous, extra-osseous, solid or conventional lesion. It frequently coexists with other benign and malignant bone tumors. Although it is considered to be reactive in nature, there is evidence that some aneurysmal bone cysts are true neoplasms. The solid variant of aneurysmal bone cyst is a rare subtype of aneurysmal bone cyst with a preponderance of solid to cystic elements. Such a case affecting the heel, an unusual site, is reported.
Case presentation: A 26-year-old Caucasian man presented with pain and swelling in his left lower extremity. A plain radiograph demonstrated an intra-osseous, solitary, eccentric mass in the front portion of the left heel. Computed tomography and magnetic resonance imaging scans showed that the lesion appeared to be sub-cortical, solid with a small cystic portion without the characteristic fluid-fluid level detection but with distinct internal septation. Bone images containing fluid-fluid levels are usually produced by aneurysmal bone cysts. The fluid-fluid level due to bleeding within the tumor followed by layering of the blood components based density differences, but it was not seen in our case. An intra-lesional excision was performed. Microscopic examination revealed fibrous septa with spindle cell fibroblastic proliferation, capillaries and extensive areas of mature osteoid and reactive woven bone formation rimmed by osteoblasts. The spindle cells had low mitotic activity, and atypical forms were absent. The histological features of the lesion were consistent with the solid variant of an aneurysmal bone cyst.
Conclusion: Solid aneurysmal bone cysts have been of great interest to pathologists because they may be mistaken for malignant tumors, mainly in cases of giant cell tumors or osteosarcomas, because of cellularity and variable mitotic activity. It is rather obvious that the correlation of clinical, radiological and histological findings is necessary for the differential diagnosis. The eventual diagnosis is based on microscopic evidence and is made when a predominance of solid to cystic elements is found. The present case is of great interest because of the nature of the neoplasm and the extremely unusual location in which it developed. Pathologists must be alert for such a diagnosis.