Case report

An 84-year-old woman was referred with a rapidly growing mass on the right side of the tongue. She had a medical history of cutaneous carcinosarcoma of the occipital region, which had been treated surgically 9 months before. She had been followed up after surgery with no evidence of recurrence and metastasis. On physical examination, a demarcated hard mass measuring 2.0 cm × 1.0 cm was seen in the right inferior surface of the tongue ( Fig. 1 ). The authors clinically diagnosed it as a benign tongue tumour, but were aware of the possibility of metastatic carcinosarcoma. An excisional biopsy with a 5 mm safety margin was removed for histological diagnosis. Histopathologically, the tumour showed carcinomatous and sarcomatous components ( Fig. 2 A ). The carcinomatous tumour cells formed nests without keratinization and the sarcomatous tumour cells showed a fibrous spindle shape. Immunohistochemically, the carcinomatous tumour cells were positive for pan-keratin (AE1/AE3; Fig. 2 B), vimentin ( Fig. 2 C), and neuron specific enolase (NSE), but negative for α-smooth muscle actin (α-SMA; Fig. 2 D) and cytokertatin 20 (CK20). The sarcomatous tumour cells were positive for vimentin ( Fig. 2 C), NSE, α-SMA ( Fig. 2 D), and CK20, but negative for AE1/AE3 ( Fig. 2 B). Based on these findings, the tumour was diagnosed as metastatic cutaneous carcinosarcoma to the tongue. CT scans of the neck and lung taken 1 month before the first visit to the authors’ clinic showed no obvious recurrence and metastasis. The patient was examined for the presence of other metastatic lesions. Positron emission tomography (PET) revealed multiple metastases to the lung, pericardium, liver, kidney, adrenal, bones, and muscles ( Fig. 3 ). Tumour recurrence in the tongue was found 2 weeks after the excisional biopsy, although tumour cells were not seen in the surgical margin. The authors recommended systemic chemotherapy including cisplatin and docetaxel, but the patient refused it. She received palliative treatment including pain control and died of the disease 2 months after diagnosis.

A bulging mass with clear boundary in the right inferior surface of the tongue.

Histological and immunohistochemical staining of the biopsy specimen. (A) A mixture of carcinomatous and sarcomatous tumour cells was seen (H&E stain, original magnification 100×). The carcinomatous tumour cells were positive for AE1/AE3 (B) and vimentin (C), but negative for α-SMA (D). The sarcomatous tumour cells were positive for vimentin (C) and α-SMA (D), but negative for AE1/AE3 (B) except a few cells in the border of the sarcomatous and the epithelial component that were positive for AE1/AE3 (arrow) (B–D original magnification 200×).

Coronal PET showing multiple metastases to the lung, pericardium, liver, kidney, adrenal, bones, and muscles.

Discussion

The gingiva is the most common metastatic site for malignant tumours to the oral cavity and the tongue is the second . The most common primary sites are the lung in men and the breast in women. The skin is the third primary site. 90% of metastatic cutaneous tumours are malignant melanoma and 10% are basal cell carcinoma . A search revealed no reported case of metastatic cutaneous carcinosarcoma to the oral mucosa.

Prognosis for patients with metastatic tumour to the oral mucosa is generally poor because most die within a year. Palliative therapies such as chemotherapy and/or radiotherapy are usually chosen for management of metastatic tumour to the oral mucosa. In the case of a single metastatic focus, surgical excision may be chosen as a therapy for control of the metastatic tumour. The authors decided to perform excisional biopsy in this case because it was a demarcated tumour, although the possibility of metastatic carcinosarcoma could not be ruled out. In the event of the tumour being diagnosed as metastatic carcinosarcoma, the authors intended to perform systemic screening to aid treatment design. From the result of this screening, they suggested systemic chemotherapy to the patient.

Carcinosarcoma is a rare malignant tumour composed of a malignant epithelial component and a malignant mesenchymal component. Cutaneous carcinosarcoma is extremely rare, and there are fewer than 50 cases to date in the literature . These tumours are commonly surgically excised. There is no evidence for the usefulness of radiotherapy or chemotherapy for cutaneous carcinosarcoma because only a small number of patients received such therapy . No report described the treatment regimen for cutaneous carcinosarcoma in detail. Chemotherapy with platinum compounds and taxanes has been reported for female genital carcinosarcoma , although the usefulness of this regimen was unclear. The authors suggested systemic chemotherapy with cisplatin and docetaxel in this case.

This tumour often has a period of recent rapid growth and metastasis occurs in 7–29% . The most common metastatic site was the lung (19%), followed by the bone and brain (5%) . A search revealed that few cases develop multiple metastases . In the present case, the tongue lesion was one of the systemic metastases showing rapid growth. This tumour was thought to be aggressive and the authors could not find such a progressive case.

Three major theories have been proposed for the pathogenesis of carcinosarcomas. The first, known as the collision theory, proposes that two individual stem cells may simultaneously and independently undergo malignant transformation and are actually separate tumours that have collided . The second, composition theory is that the spindle cell component is a reaction to the carcinoma . The third, divergence theory is that individual elements are derived from a single common precursor cell . In most cases of oesophageal carcinosarcoma, it has been suggested that the sarcomatous component generally results from differentiation of squamous cell carcinoma cells into mesenchymal tumour cells. The reasons for this suggestion are that most carcinosarcomas contain a transitional zone between carcinomatous and sarcomatous components and that identical genetic alterations are observed in both components . The pathogenesis of most oesophageal carcinosarcomas has been linked to divergence theory and this theory has also been applied to cutaneous carcinosarcoma . When considering the pathogenesis of carcinosarcoma, the presence of a transitional zone or genuine sarcomatous components such as osteoblastic or rhabdomyoid features, or both, is a key feature. Differential diagnosis with spindle cell carcinoma or reactive spindle cell is important in the absence of genuine sarcomatous components.

In the present case, the sarcomatous component is considered a true tumour, since it showed cellular atypism, abnormal increase of mitosis, a negative reaction with AE1/AE3 and a positive reaction with vimentin. Immunohistochemistry revealed a few sarcomatous cells positive for AE1/AE3 in the border of the sarcomatous and the epithelial component. This suggested the presence of a single common precursor cell. The pathogenesis of this case was considered to be divergence theory.

In conclusion, the authors presented a case of metastatic cutaneous carcinosarcoma to the tongue, which is the first case of metastatic carcinosarcoma to the oral cavity. The pathogenesis of carcinosarcoma is unclear, but this tumour was very aggressive, resulting in poor prognosis. These metastatic tumours are thought to be more aggressive and the prognosis is very poor. More research to elucidate the pathogenesis of carcinosarcoma and to develop an effective therapy are needed.