Would you send Oncotype Dx for a premenopausal patient with a pT2N0 ER/PR+ lobular breast cancer that was diagnosed during the first trimester of pregnancy?

This is a complicated question. I feel as though more information would be helpful. I will try to address specifics that I consider when managing such cases that I hope are helpful. Appreciate others' thoughts as well.

First, how sure are we that this patient is N0? I cannot count the number of clinical N0 lobular cancers that end up having nodal involvement. At the least, I would want an MRI in addition to axillary ultrasound to evaluate the extent of disease. Any nodes that radiology mentions...

I would not. I do not believe that Oncotype is validated in pregnancy.

Oncotype, like other molecular prognostic assays, is valuable in its prognostication for lobular cancer. Studies about its predictive value in ILC have been less conclusive (Chen et al., PMID 30565472), and few ILCs are classified as high risk by the assay. PR-negativity and high grade are more likely to yield higher Oncotype scores (Wu et al., PMID 31234641).