Sarcomatoid carcinomas are uncommon, high-grade tumors, predominantly composed of spindle cells. Only a few cases arising in the penis have been reported. The aim of this study is to better define the clinicopathologic features of this neoplasm. A total of 400 cases of squamous cell carcinoma of the penis were reviewed from which 15 sarcomatoid carcinomas (4%) were identified. Clinical and pathologic features were evaluated in all cases. Immunohistochemical studies for expression of AE1/AE3, Cam 5.2, 34betaE12, EMA, vimentin, muscle specific actin, smooth muscle actin, desmin, S-100, p63, and p53 and in situ hybridization studies for HPV were performed in 5 cases. Information about lymph node status was available in 9 cases, and follow-up in 5 cases. The mean age was 59 years, and mean tumor size was 5 cm. Grossly, most tumors were large, polypoid, and ulcerated masses frequently affecting the glans (93%) and deeply invading corpora cavernosa (80%) and skin. Microscopically, the lesions were predominantly composed of atypical spindle cells disposed in interlacing fascicles, resembling fibrosarcoma or leiomyosarcoma, sometimes admixed with pleomorphic giant cells mimicking malignant fibrous histiocytoma. One case was predominantly composed of myxoid areas. Less frequent and focal patterns were pseudoangiomatous and epithelioid. Mitotic figures were numerous, and necrosis was prominent. Foci of heterologous differentiation toward bone (osteosarcomatous component) were present in 1 case. Four cases showed a minor mixed component of usual, papillary, verrucous, and basaloid carcinoma. Intrapenile metastasis ("satellitosis") was present in 4 tumors. One of the cases was multicentric with a separate independent focus of well-differentiated carcinoma with pseudohyperplastic features. Associated low- and high-grade squamous intraepithelial lesions were noted in 73% of the cases. Immunohistochemical studies and HPV in situ hybridization were done in 5 cases. The spindle cells were diffusely positive for vimentin and p53 and showed at least intermediate expression of 34betaE12 and p63 in all cases. EMA and AE1/AE3 were focally positive in 60% of the cases, and Cam 5.2 was focally positive in 1 case. Tumor cells failed to express muscle specific actin, smooth muscle actin, desmin, and S-100. HPV in situ hybridization was negative in all cases. Inguinal metastases were present in 89% of the cases. Two of five patients with adequate follow-up died of disease within 8 months of the diagnoses. In conclusion, penile sarcomatoid carcinomas are unusual, large, and aggressive tumors usually associated with lymph node metastasis and poor outcome. Differential diagnoses include sarcoma and melanoma. Cytokeratin 34betaE12 and p63 appear to be the more specific and sensitive markers to categorize these tumors as epithelial. Diffuse immunoreactivity for p53, compared with a more basal and focal reactivity in differentiated squamous cell carcinoma, may be indicative of a late mutation in the natural progression of the disease.