Inclusion Criteria:

- Participant is 18 years of age or older.

- Participant is scheduled for standard clinical 18F-FDG PET/CT scan or 131I therapy
within the Nuclear Medicine Service at Main Hospital.

- Patients must have pathologic lymph node metastases in the neck, axillary or inguinal
area (do not need to be biopsy proven) from either leukemias, lymphomas: , Head and
Neck cancers (e.g. tonsillar, nasopharynx, tongue carcinoma, breast cancer or
melanoma;or lymphoma or tonsillar or squamous cell carcinoma with metastases in the
neck region for PET/CT imaging, or thyroid cancer for thyroid ablation therapy. Any
other more infrequent cancer metastasizing with nodal metastasis in the neck, axilla
and inguinal regions to cervical lymph nodes is eligible as well as the primary goal
is to image pathological (i.e. hypermetabolic) lymph nodes.

- Patients with hypermetabolic activity and uptake in the neck,axilla, breast and
inguinal region on scan, defined visually as significant lesion suspicious for
malignancy by a nuclear medicine physician or trainee.

Exclusion Criteria:

- Patients imaged for Cerenkov luminescence are going to be required to be in a
darkened enclosure for at least 10 minutes and sit still during image acquisition,
potentially covered by a dark cloth in case that the ambient light level remains too
high for the ultra-sensitive camera. Any conditions that would prevent this will
exclude the patients.

- There are no other past medical, physiological or demographic concerns. This includes
any patients with skin blemishes that are present at the dermis over the tumor, as
these are of particular interest for use of this technique.