Myxoid leiomyosarcoma.

A series of 13 myxoid leiomyosarcomas (LS) is presented. Seven were from genital and six from extragenital sites and most tumours were large. The myxoid matrix in some tumours separated individual tumour cells; occasionally the myxoid areas were trabecular in shape, resulting in a plexiform tumour pattern; in other tumours there were many closely spaced small mucoid pools which produced a pseudoglandular pattern; in one tumour the pools were large and confluent, and macroscopically evident as gelatinous areas. Four patients who were followed up and whose tumours had shown an absent or very low mitotic rate, nevertheless developed recurrences or metastases; hence a low mitotic count was an unreliable prognostic criterion. The myxoid LS studied did not differ in clinical behaviour and prognosis from the more common solid counterparts. Myxoid LS should be included in the differential diagnosis of any myxoid malignant soft tissue tumour.