Microsatellite instability is an important characteristic of many tumor types especially those associated with hereditary non-polyposis colorectal carcinoma (HNPCC) syndrome. Microsatellite alterations in 50% of primary small cell lung carcinoma (SCLC) have been found. These alterations were also found in the sputum. Because neoplastic characteristics such as decreased strand stability9 and ras mutations have been found in the plasma DNA of cancer patients, we looked for microsatellite alterations in the plasma of SCLC patients. A microsatellite alteration was present in 16 out of 21 (76%) SCLC tumors and in 15 out of 21 (71%) plasma samples. In one case, the alteration was present only in the plasma DNA. If confirmed in larger studies, microsatellite analysis of plasma DNA might constitute a new tool for tumor staging, management and, possibly, detection.

A study of 80 well-differentiated osteosarcomas, 16 from the Mayo Clinic files and 64 from our consultation files, revealed that males and females were about equally affected, most of the patients were young adults, and skeletal distribution was similar to the distribution seen in conventional osteosarcoma. Radiographs generally showed poor margination, suggestive of malignancy. Histologically, the tumors were composed of spindle cells with only minimal atypia. Some tumors had bone spicules similar to those seen in fibrous dysplasia. An invasive growth pattern was the most helpful feature in differentiating low-grade osteosarcoma from fibrous dysplasia. Initial treatment was highly variable. Local excision was almost always associated with recurrence. Wide excision was almost never followed by recurrence. The recurrent tumor was a high-grade, conventional osteosarcoma in 15% of the patients, and this was associated with a poor prognosis. Wide excision seems to be the treatment of choice for this very rare variant of osteosarcoma.

S ialolithiasis is a relatively frequent occurrence; however, cases of sialolithiasis originating around a "foreign body" nidus are rare. We describe a patient with submandibular sialolithiasis organized around a vegetal nidus and discuss the etiology of the case.

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Chondroblastoma of the bone is a benign tumor that has well-characterized radiographic and histologic features. It tends to affect the epiphyseal ends of long bones in men during the second and third decades of life. The tumor is located more frequently at other sites in older patients. The treatment of choice is complete curettage with bone grafting, which in our series provided local control in 82% of patients at 2 years' follow-up. Recurrent tumors usually can be treated in the same manner.