Solid tumors causing palpable adenopathy typically reflects local spread. LNs are typically firm, fixed and stuck to one another. Many cancers can cause adenopathy which can't be palpated (e.g. mediastinal or retroperitoneal nodes).
Breast cancer: first site of spread is often ipsilateral axilla
Head and Neck squamous cell: first spreads to ipsilateral lymph nodes of neck
Thyroid cancer: first spreads to ipsilateral lymph nodes of neck
Melanoma: first spread can be to nearest lymph nodes (e.g. inguinal, axillary); though as progresses, can present anywhere
Advanced lung, esophageal cancer: Right supraclavicular nodes
Advanced lung, lymphoma, gastric, other intra-abdominal cancer: Left supraclavicular (Virchow's) nodes
Advanced intra-abdominal (e.g. colon): Periumbilical (Sister Mary Josephs) nodes