Florid Lobular Intraepithelial Neoplasia with Signet Ring Cells, Central Necrosis and Calcifications: A Clinicopathological and Immunohistochemical Analysis of Ten Cases Associated with Invasive Lobular Carcinoma

Background and Aims. In its most florid form, classic lobular intraepithelial neoplasia (UN) proliferates to form a solid mass of tumor cells that fill and expand the duct within the terminal duct lobular unit lumen. Foci such as these can develop central necrosis and calcifications, detectable on mammograms. The immunohistochemical expression of E-cadherin has been found to be absent in all reported examples of LIN with necrosis. The occurrence of LIN composed entirely of signet ring cells with central necrosis is extraordinarily rare. Methods. We described 10 of these cases to illustrate this uncommon morphologic pattern of LIN. The cases were encountered during routine clinical practice of the authors over a 5-year period at the Oncology Hospital of the Mexican Social Security Institute in Mexico City. Cases were comprised of several (> 6) foci of LIN with signet ring cells as well as with comedo-type necrosis. Results. Age of patients ranged from 45-75 years (mean age: 51.2 years). The indications for biopsy were calcifications (n = 7) and mass (n = 3) on mammograms. Luminal necrosis was seen in all ten cases and calcifications in seven cases. Eight cases had associated invasive carcinoma, including six lobular carcinomas and one composite carcinoma (lobular and ductal). All cases showed a lack of E-cadherin membrane staining and a diffuse cytoplasmic immunoreactivity for high molecular weight keratin, positivity for estrogen receptors and progesterone receptors was present in 9/10 and 8/10 of cases, respectively. Conclusions. LIN composed entirely of signet ring cells can develop macro-acini, central necrosis and calcifications. These cases are frequently associated with invasive lobular carcinoma at the time of initial presentation. (C) 2010 IMSS. Published by Elsevier Inc.