Inflammatory myxoid tumor of the soft parts with bizarre giant cells.

We present five cases of a tumor which we named inflammatory myxoid tumor of the soft parts with bizarre giant cells and which is often misdiagnosed as a malignant neoplasm. The tumors were located in the soft tissues of the fingers and hand and were 1 to 2.5 cm in the largest diameter (median 2 cm). The tumors were divided by fibrous septa into lobules. The lobules were composed of numerous proliferating capillaries and tumor cells, both set in copious myxoid extracellular matrix. Variously dense inflammatory infiltrate represented by numerous lymphocytes and plasma cells and sparse neutrophil leukocytes surrounded the capillaries. The tumor cells had one, two, or more nuclei. The nuclei of the tumor cells were vesicular, often indented or cleaved and they usually had one small nucleolus. The cytoplasm displayed characteristic clear vacuoles filled with mucous substances. In some of the tumor cells the cytoplasmic vacuoles filled the whole cytoplasm and compressed or indented the nucleus. Such cells had an appearance of signet ring cells. The cytoplasm of some of the cells often contained lymphocytes and leukocytes. All four patients with follow-up were without signs of recurrence and metastasis 2, 4, 6 and 7 years after the diagnosis.