Lautenberg spokesman Caley Gray said the 86-year-old Democrat was attending a Tuesday afternoon hearing on Toyota recalls. Earlier, he cast votes on two judicial appointments.
The Senate's second-oldest member was hospitalized on Feb. 15 after suffering a fall at home in New Jersey. The following day he was treated for a bleeding ulcer, and it was announced Feb. 19 that the B-cell lymphoma was found in the ulcer.
He was discharged Thursday.
Lautenberg did not attend a Monday morning meeting with New Jersey Gov. Chris Christie and the state's congressional delegation.