Are palpable supraclavicular lymph nodes usually cancer?

It depends. Sometimes these, and other nodes are palpable because of infection. Sometimes cancer can do it. Rock hard nodes would more likely mean cancer, while soft, painful ones would point to infection.
Not necessarily. Supra-clavicular lymph nodes may be enlarged due to local or systemic infections. Unilateral enlargement of supra-clavicular lymph nodes would be more suspicious and warrant exclusion of malignancy.

Related Questions

Is it possible to have several palpable bilateral supraclavicular lymph nodes and not be related to cancer?

Yes. There are. Indeed many causes of benign, or at least not malignant nodes. Sarcoid is a common one, but drug reactions, infections, tb, HIV are some of a long list of others. Read more...
Yes. Several bilateral enlarged nodes in the neck are more likely to be due to infection, locally or systemically. However, enlarged nodes may be due to lymphoma/leukemia and metastatic tumors. If the enlargement has persisted more than a few days, consult your doctor for a more detailed examination and investigation. Read more...

Can esophageal cancer spread to supraclavicular lymph nodes without causing any symptoms?

Sadly yes. Esophagus is a muscular tube that can stretch, so often no symptoms until it can't . Also has no outer membrane surrounding it so easier to spread outside the organ itself. Read more...
Unfortunately yes. Supraclavicular lymph node spread is possible with out symptoms from the primary tumor. Supraclavicular lymph node metastasis does not preclude treatment, but likely rules out surgery. Read more...
Yes. Esophageal cancer can go unnoticed for a while. I have seen patients present with very advanced disease without a long course of symptoms. Supraclavicular lymph nodes without a clear explanation need to be evaluated carefully. A number of tumors can spread to the supraclavicular nodes including lung, esophagus, stomach and ovarian cancers. Read more...
Yes. The symptom is the inability to swallow food or liquid comfortably. Esophageal cancer is generally circumferential, like a doughnut. The hole or the lumen becomes smaller as the cancer grows, making it difficult for food and then liquid to pass through. However, that hole can be as small as 6mm in diameter before symptoms appear. So esophageal ca often has no symptoms. Read more...

Confused - in a healthy young adult, are pea-sized neck and supraclavicular lymph nodes for months normal or should they not be palable?

Should be ok. Especially if you are thin, nodes less than 1 cm are usually nothing to worry about. If they persist or grow, would recommend an evaluation. This could involve imaging. Some people get biopsies. Read more...