A spindle cell tumor of unknown origin and diffuse bone marrow involvement in a patient with hypercalcemia

Metastasis of unknown origin in bone marrow is infrequent, although, when it occurs, adenocarcinoma is the most common histologic type. Involvement of bone marrow by a spindle cell tumor and presentation with hypercalcemia are very rare.

This report describes a 21-year-old man with diffuse bone marrow involvement from a spindle cell tumor.

The patient presented with low back pain, anemia, thrombocytopenia, azotemia, and hypercalcemia. Bone marrow biopsy revealed a spindle cell tumor that was positive for vimentin staining but whose primary site could not be identified. A bone marrow scan revealed absence of uptake, which suggested systemic disease. We treated this case as a type of sarcoma by giving combined chemotherapy consisting of vincristine, actinomycin-D and cyclophosphamide. The patient showed a clinical response for seven months, but the disease progressed despite chemotherapy and he died one year after diagnosis.

We have documented a rare case of spindle cell tumor involving bone marrow without evidence of the tumor's primary site.