Unusual small bone metastases from epithelial malignancies: diagnosis by fine-needle aspiration cytology with histologic confirmation.

Although epithelial malignancies can have bone metastases, involvement of small bones is exceedingly rare, representing either first manifestation of an occult carcinoma or late disseminated disease. Small bone metastases may mimic primary skeletal diseases leading to misdiagnosis and delayed treatment. We report three cases of metastatic epithelial malignancies diagnosed by computed tomography (CT)-guided fine-needle aspiration (FNA) biopsy in two patients with lytic calcaneal lesions and a patellar lesion in a third patient; all with histologic confirmation. Case 1, a 63-year-old female, presented with heel pain. FNA and tissue biopsy of the calcaneus revealed a clear cell malignancy consistent with a renal primary. Follow-up abdominal CT scan revealed a renal lesion consistent with renal cell carcinoma. Case 2, a 37-yr-old male with squamous cell carcinoma of the esophagus, presented with foot pain. FNA and tissue biopsy of the calcaneous revealed metastatic squamous cell carcinoma. Case 3, a 52-yr-old male with a history of squamous cell carcinoma of floor of mouth, presented with knee pain and swelling. FNA and tissue biopsy of the patella revealed metastastic squamous cell carcinoma. To the best of our knowledge, this is the first complete FNA cytology report with histologic confirmation of unusual small bone metastases of the feet and patella from epithelial malignancies and shows the value of FNA cytology in establishing a correct diagnosis, and excluding primary skeletal diseases.