IANAQSA! That data doesn't put you in scope, but you're probably in scope anyway, but dint of whatever relationship you're in that gets you access to that non-scoped data.
To quote PCI-DSS 3.2 (emphasis as per source):
The primary account number is the defining factor for cardholder data. If cardholder name, service code, and/or expiration date are
stored, processed or transmitted with the PAN, or are otherwise
present in the cardholder data environment (CDE), they must be
protected in accordance with applicable PCI DSS requirements.
If you never have the full Primary Account Number, then you do not have cardholder data. That is not to say that you're not subject to the DSS, however. Even a merchant who outsources all handling of their card data to their service provider is subject to something like the SAQ A (Self Assessment Questionnaire).
What you're describing (first 6, last 4) is called Truncation and is described in section 3.4 of the DSS. So someone - your service provider? - is truncating card numbers and handing those to you in lieu of card numbers. If that's the case, your service provider should be authoritative for helping you figure out what your scope is under the DSS.
It comes down to this:
PCI DSS applies to all entities involved in payment card
processing—including merchants, processors, acquirers, issuers, and
Do those truncated numbers put you in scope? No. If you're receiving truncated numbers, are you likely in a relationship that makes you subject to the PCI DSS as above? Very likely, yes.