Faculty Bibliography

BACKGROUND/PURPOSE/OBJECTIVE:Tumor heterogeneity is a now well-recognized phenomenon that can affect the classification, prognosis and treatment of human cancers. Heterogeneity is often described in primary breast cancers based upon histologic subtypes, hormone- and HER2-receptor status, and immunolabeling for various markers, which can be seen within a single tumor as mixed cellular populations, or as separate discrete foci. EXPERIMENTAL DESIGN/METHODS/UNASSIGNED:Here, we present a case report of a patient's primary breast cancer that had two separate but adjacent histologic components, one that was estrogen receptor (ER) positive, and the other ER negative. Each component was subjected to whole exome sequencing and compared for gene identity to determine clonal origin. RESULTS:Using prior bioinformatic tools, we demonstrated that both the ER positive and negative components shared many variants, including passenger and driver alterations. Copy number variations also supported the two components were derived from a single common clone. CONCLUSIONS:These analyses strongly suggest that the two ER components of this patient's breast cancer were derived from the same clonal origin. Our results have implications for the evolution of breast cancers with mixed histologies, and how they might be best managed for optimal therapy.

Primary central nervous system T-cell lymphoma (PCNSTCL) is rare, accounting for 2% of CNS lymphomas. We report the first case of PCNSTCL with aberrant expression of CD20 and CD79a in an 81-year-old man with a left periventricular brain mass. A biopsy revealed dense lymphoid infiltrate consisting of medium-sized cells in a background of gliosis and many histiocytes. The lymphoid cells were positive for CD2, CD3, CD7, CD8, T-cell intracellular antigen-1, granzyme B, CD20, and CD79a and negative for CD4, CD5, PAX-5, OCT-2, BOB-1, human herpes virus-8, and Epstein-Barr virus-encoded small RNAs. Molecular studies revealed clonal TCR-β and TCR-γ gene rearrangements and negative immunoglobulin gene rearrangements. The patient was treated with chemotherapy (vincristine and methotrexate) and rituximab, but he died 1 month after the diagnosis. This is a unique case that emphasizes the use of a multimodal approach, including a broad immunohistochemical panel and molecular studies in lineage determination for lymphomas with ambiguous phenotype.