RATIONALE: Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die. Combining more than one drug may kill more tumor cells.

PURPOSE: Phase II trial to study the effectiveness of combining cyclophosphamide, methotrexate, and fluorouracil in treating patients with Merkel cell cancer.

OBJECTIVES: I. Investigate the ability of the Southwest Oncology Group Melanoma Committee to enroll patients with unresectable Merkel cell carcinoma that is local-regional or metastatic. II. Determine the overall survival rate and objective response rate of these patients after treatment with cyclophosphamide, methotrexate, and fluorouracil.

OUTLINE: Patients are stratified according to local-regional disease versus metastatic disease. Patients receive cyclophosphamide IV, methotrexate IV, and fluorouracil IV on day 1. Courses repeat every 21 days for up to 2 years in the absence of disease progression or unacceptable toxicities. Patients are followed every 6 months for 2 years, then annually thereafter.

PROJECTED ACCRUAL: A total of 80 patients (40 patients per stratum) will be accrued for this study.

DISEASE CHARACTERISTICS: Histologically proven unresectable Merkel cell carcinoma Local-regional OR Metastatic Bidimensionally measurable disease If all known sites previously irradiated, disease must be progressive CNS metastases allowed if not only site of measurable disease No pleural effusions or ascites

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: SWOG 0-2 Life expectancy: Not specified Hematopoietic: Absolute granulocyte count at least 1500/mm3 Platelet count at least 100,000/mm3 Hepatic: Not specified Renal: Not specified Other: Not pregnant or nursing Fertile patients must use effective contraception No other prior malignancy within 5 years except: Adequately treated basal cell or squamous cell skin cancer Adequately treated stage I or II cancer In situ cervical cancer

PRIOR CONCURRENT THERAPY: Biologic therapy: No prior biologic therapy or immunotherapy No concurrent immunotherapy Chemotherapy: No prior chemotherapy for metastatic disease At least 4 weeks since prior adjuvant chemotherapy No prior adjuvant cyclophosphamide, methotrexate, or fluorouracil No other concurrent chemotherapy Endocrine therapy: No concurrent hormone therapy Radiotherapy: See Disease Characteristics At least 14 days since prior radiotherapy Surgery: At least 2 weeks since prior surgery