The overlooked primary : bladder cancer metastases on dry bone : a study of the 20th century CAL Milano Cemetery Skeletal Collection

Objective: The aim of this article is to provide additional documentation of bone metastases to help anthropologists recognize the condition and potentially suggest the diagnosis of bladder carcinoma in differential diagnosis. Materials and methods: Thirteen individuals clinically diagnosed with bladder carcinoma from the 20 th century Milano Cemetery Skeletal Collection were macroscopically studied to document bone metastases in bladder cancer. Results: Bone metastases were found through macroscopic observation in three individuals or 23% of the study sample. Metastases were mostly of a mixed nature (45%), although both osteoblastic (13%) and osteolytic (9%) also occurred. In particular, mixed and osteoblastic metastases exhibited different distribution patterns, even when affecting the same bones. The vertebrae (24.7%), skull (12.9%), ribs (11.7%), proximal humeri (7.8%), pelvis (5.2%), proximal femora (2.6%), sacrum (1.3%) and sternum (1.3%) were the most commonly affected. Osteolytic lesions included coalescing superficial pits or lesions perforating the bone cortex. Proliferative lesions manifested as spongiosclerosis or periosteal new bone. Mixed metastases were osteolytic lesions exposing a thickened trabecular bone or coalescent porosity with reactive new bone. Conclusions: Bladder carcinoma metastases were mostly mixed, exhibiting periosteal reactions, perforations of bone cortex, spongiosclerosis and coalescing porosity. Significance: Bladder carcinoma is rarely considered in the differential diagnosis of the primary organ. This study reports the macroscopic aspect of bone metastases in bladder carcinoma and may help anthropologists diagnose the condition in skeletons. Limitations: Absence of evidence is not evidence of absence; some lesions may have been hidden from macroscopic observation and therefore missed. Further research: Radiographic analysis and comparison with other neoplasms should provide additional details for the diagnosis of bladder cancer bone metastases.