• Duration of response and survival, and the safety and toxicity profile in patients, with squamous cell carcinoma of the skin. [ Time Frame: 6 Years ] [ Designated as safety issue: Yes ]
• Modulation of biological targets following daily administration of ZD1839 (250 mg) in patients with biopsy-proven SCC of the skin. [ Time Frame: 6 Years ] [ Designated as safety issue: No ]

• The secondary objectives are to determine the duration of response and survival, and the safety and toxicity profile in patients, with squamous cell carcinoma of the skin. [ Time Frame: Contact patients for survival until death every 56 days after ZD1839 has stopped and completion of the trial. ] [ Designated as safety issue: Yes ]
• Exploratory objectives are to evaluate modulation of biological targets following daily administration of ZD1839 (250 mg) in patients with biopsy-proven SCC of the skin. [ Time Frame: Skin biopsies and buccal smears are optional. Buccal smears to be performed pretreatment, and on Days 2, 3, and 4. ] [ Designated as safety issue: No ]

Primary Objectives:

1. To explore the activity of ZD1839 administered to patients with SCC of the skin who have locoregional recurrence and/or metastatic disease and are not amenable to a curative local approach.
2. Activity is defined in terms of objective response rate, based on Union International Contre le Cancer (UICC)/World Health Organization (WHO) Criteria.

Secondary Objectives:

1. To determine the duration of response and survival and the safety and toxicity profile in patients with squamous cell carcinoma of the skin.
2. To evaluate modulation of biological targets following daily administration of ZD1839 (250 mg) in patients with biopsy-proven squamous cell carcinoma of the skin.

ZD1839 is a new drug that may slow or stop cell growth in humans.

Epidermal growth factor receptor (EGFR) may be involved in certain types of cancer, including squamous cell carcinoma of the skin. When EGFR is stimulated, a series of chemical reactions starts that results in a tumor being "told" to grow. ZD1839 tries to stop these reactions by blocking EGFR. This may stop tumors from growing.

Before treatment starts, participants will have a full medical history and physical exam. Participants will have routine lab tests (including about 2-4 teaspoons of blood), ECG (test to measure the electrical activity of the heart), a chest x-ray, and a CT (computerized tomography) scan or MRI (magnetic resonance imaging). These are done to learn the status of a participant's disease. Women able to have children must have a negative blood pregnancy test.

In this study, participants will take ZD1839 by mouth daily. Once the treatment has started, participants will return to the clinic before every treatment cycle (every 4 weeks) for the first 4 months then every 8 weeks thereafter. At these visits, participants will have a physical exam and blood tests will be performed. About 2-4 teaspoons of blood will be drawn at each visit. The doctor will also check on how participants are tolerating ZD1839 (side effects). Every 8 weeks, participants will have their tumor evaluated by radiographic scans. This may include either a CT or MRI and a chest X-ray.

During treatment, participants should not take any other medication, including non-prescription drugs such as aspirin or herbal products without the approval of their doctor.

Participants will continue taking the trial drug until the tumor grows, a severe side effect occurs, they withdraw consent, or the study is closed. The study will be closed 12 months after the last participant is enrolled.

THIS IS AN INVESTIGATIONAL STUDY. The FDA has approved ZD1839 for the treatment of advanced lung cancer, but the FDA has authorized ZD1839 for research only in the treatment of skin cancer.About 40 participants will take part in this study. All will be enrolled at M.D. Anderson.

Inclusion Criteria:

1. Provision of written informed consent.
2. Pathologically confirmed locoregional recurrence and/or metastatic SCC of the skin not amenable to curative therapy (i.e., surgery or radiation).
3. Evaluable and/or measurable disease. (Based on UICC/WHO Criteria)
4. ECOG performance status 0-2.
5. Adequate hematologic function as defined by an absolute neutrophil count >= 1,500/mm3, a platelet count >= 100,000/mm3, a WBC >= 3,000/ mm3, and a hemoglobin level of >= 9 g/dl.
6. Up to one prior chemotherapy regimen.
7. At least a 2-week recovery from prior therapy toxicity.
8. Age 18 years or older.
9. Disease free from a previously treated malignancy, other than the disease under study, for greater than 3 years. Patients with a history of a previous basal cell carcinoma of the skin or pre-invasive carcinoma of the cervix, completely resected breast cancer will not be excluded.
10. Women of childbearing potential and men must be willing to practice acceptable methods of birth control to prevent pregnancy.

Exclusion Criteria:

1. Prior ZD1839 or other EGFR inhibiting agents.
2. Other co-existing malignancies or malignancies diagnosed within the last 3 years with the exception of basal cell carcinoma or cervical cancer in situ.
3. Any unresolved chronic toxicity greater then CTC grade 2 from previous anticancer therapy.
4. Incomplete healing from previous oncologic or other major surgery.
5. Concommitant use of phenytoin, carbamazepine, barbiturates, rifampicin, St John's Wort. Patients taking anticoagulants must have coagulation parameters followed (i.e., PT or PTT).
6. ANC less than 1,500/mm**3 or platelets less than 100,000/mm**3.
7. Serum bilirubin greater than 1.25 times the upper limit of reference range (ULRR).
8. In the opinion of the investigator, any evidence of severe or uncontrolled systemic disease, (e.g., unstable or uncompensated respiratory, cardiac, hepatic, or renal disease).
9. Alanine amino transferase (ALT) or aspartate amino transferase (AST) greater than 2.5 times the ULRR if no demonstrable liver metastases or greater than 5 times the ULRR in the presence of liver metastases.
10. Evidence of any other significant clinical disorder or laboratory finding that makes it undesirable for the patient to participate in the trial.
11. Pregnancy or breast feeding (women of child-bearing potential)
12. The patient has an uncontrolled seizure disorder or active neurological disease.
13. The patient has received any non-approved or investigational agent(s) within 30 days before Day 1 of study treatment.
14. Known, severe hypersensitivity to ZD1839 or any of the excipients of this product.
15. Any evidence of clinically active ILD (patients with chronic, stable radiographic changes who are asymptomatic need not be excluded).