INVASIVE MICROPAPILLARY CARCINOMA OF THE BREAST - A NEW SPECIAL TYPE OF INVASIVE MAMMARY-CARCINOMA

After reviewing 986 consecutive cases of breast carcinoma from our fil es, 27 ductal infiltrating cancers showing micropapillary differentiat ion in invasive areas (MP) were selected. Special immunohistological a nd ultrastructural techniques were used, and their characteristics com pared to those of the Not Otherwise Specified type of carcinomas (NOS) . Diagnostic areas of MP were HvE sections and were composed of solid or tubular neoplastic cell groups inside a spongy background, where th ey appeared to swim in aqueous or mucinous material. Neoplastic cells displayed the reverse polarity typical of the papillary phenotype. Thi s was revealed by the detection of acid mucinous rims, lineal deposits of EMA substances, and microvilli in a peripheral position, even in a reas where the micropapillae resembled tubules. Histologically, most M P were mixed with NOS, Papillary, or Mucinous patterns, but regardless of the extension of their micropapillary diagnostic component, their tumour size, or their WHO histological grade, two thirds had extensive lymphatic vessel invasion and all the cases presented massive axillar y lymph node metastasis. Six of the twelve patients followed died with in a mean of 22 months. In conclusion, we propose the recognition of ' 'Invasive Micropapillary Carcinoma of the Breast'' as a new special en tity with a potentially high degree of aggressiveness.