This mnemonic has been commonly used to recall the differential diagnosis for a solitary lung mass: CASH PLEASe
C – Cancer
A – Abscess
S – Solitary Metastasis
H – Hamartoma
P – Pseudotumor
L – Lymphoma
E – Echinococcus
A – Actinomyces
S – Sequestration
See a case discussion of solitary lung mass here.