RATIONALE: Studying samples of tissue and blood in the laboratory from patients treated with ipilimumab with or without sargramostim may help doctors learn more about the effects of ipilimumab and sargramostim on cells. It may also help doctors understand how well patients respond to treatment.

PURPOSE: This research trial studies tissue and blood biomarkers in patients with stage III melanoma or stage IV melanoma treated with ipilimumab with or without sargramostim.

OBJECTIVES:

• To compare the pathology of primary melanomas, melanoma metastases, and post-treatment melanoma metastases in relation to clinical outcomes for patients receiving ipilimumab plus sargramostim (GM-CSF) and patients receiving ipilimumab alone.
• To determine the effects of the addition of systemic GM-CSF to ipilimumab on effector immune function in patients with metastatic melanoma.
• To determine the effects of the addition of systemic GM-CSF to ipilimumab on regulatory immune function in patients with metastatic melanoma.
• To determine the effects of the addition of systemic GM-CSF to ipilimumab on anti-tumor humoral immunity in patients with metastatic melanoma.

OUTLINE: Serum, peripheral blood mononuclear cells, and tumor tissue (from primary tumor and post-treatment biopsies) samples are analyzed for biomarkers predictive of clinical outcomes, immune function, and anti-tumor humoral immunity by IHC, RT-PCR, flow cytometry, ELISPOT assays, and ELISA.

DISEASE CHARACTERISTICS:

• Diagnosis of measurable unresectable stage III or stage IV melanoma
• Treated with ipilimumab with or without sargramostim on clinical trial ECOG-E1608
• Primary tumor tissue and optional post-treatment biopsies of tumors from easily accessible tissues

PATIENT CHARACTERISTICS:

• ECOG performance status 0 or 1

PRIOR CONCURRENT THERAPY:

• See Disease Characteristics

Samples from patients who participated in E1608 and provided samples for research.