Tubular elements in lymph node metastases from lobular carcinomas with or without tubule formation

Invasive lobular carcinomas may demonstrate tubule formation both at the primary and at metastatic sites. A series of 135 invasive lobular carcinomas scrutinously screened for tubular elements were used, and tumours with axillary lymph node metastases were selected for review. Two observers blinded to the histology of the primary tumours independently and then together looked at all slides from lymph node metastases of 50/52 cases having nodal involvement searching for tubular structures. Altogether 4 lymph nodes from 4 tumours were identified as harbouring tubules, 1 from a primary with tubular elements, and 3 from carcinomas without tubular elements identified in the primary. Tubule formation was generally focal (< 10%) in most primaries (including the one with similar metastasis), therefore, by chance identification and sampling bias may be contributory factors to the discrepant primary and metastatic tubular elements, but microenvironment related factors may also be involved in a site dependent development of tubules in lobular carcinomas. Identifying tubules in a metastasis associated with a non-tubule-forming primary lobular carcinoma should not obviously mandate the search for a similar tubule-forming primary tumour.