A molecular reappraisal of matrix-producing breast metaplastic carcinoma highlighted by PLAG1 and MYC rearrangements.

Background: Very little is currently known about molecular alteration of matrix-producing carcinoma of the breast. However, the morphological similarity with other neoplasm with a myxo-chondroid component is remarkable. In this pilot study we evaluated the molecular alterations involving and genes in 12 cases of matrix producing carcinoma.

Methods: We evaluated rearrangements as Break-Apart and Gene Copy Gain, and as amplification and polysomy in 12 cases of matrix producing carcinoma using a FISH method.

Results: Among the 12 cases of matrix producing carcinomas we found that the three cases harboring amplification were all negative for break-apart; four cases with polysomy were associated to break-apart and high Gene Copy Number; among four cases wild type for , three showed a - break-apart signal and of them two died with disease. One of the deceased patients showed an amplification of with - wild-type and the other showed a break-apart (6%) and a wild-type.

Conclusion: This is the first report to the best of our knowledge that shows a possible correlation between a matrix producing carcinoma with and involvement in the development and progression of this kind of tumor. We can suppose that MYC amplification behaves in an aggressive way together with PLAG1- break-apart in the cases of matrix producing carcinoma presented here. The gene copy gain is a useful diagnostic tool in the case of difficult diagnosis because an increase was observed in more than 50% of cases.