The "Dance Moms" star got some fresh air outside her rehabilitation center on a hot summer day in L.A. Tuesday. She recently completed her fifth round of chemotherapy to treat Burkitt lymphoma ... which she was diagnosed with in April.

Abby's not been shy about keeping fans posted on her progress, either ... including recovery updates and photos from her back surgeries.

She's also revealed she's due for 6 cycles of chemo to fight the rare form of non-Hodgkins Lymphoma ... so she's approaching the finish line.