“…It should be noted that another crucial differential diagnosis is metastatic axillary lymphadenopathy from an occult breast primary. The clavipectoral fascia can be used to differentiate between the two, with any histologically confirmed axillary malignancy superficial to the clavipectoral fascia being CATS, while any mass beneath it being defined as axillary lymphadenopathy [ 13 ]. Although we couldn't confirm the presence of clavipectoral fascia on MRI in our case, the mass's superficial location suggested CATS instead of metastatic axillary lymphadenopathy.…”