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WHO Classification of Tumours
Mixed tumor, malignant, NOS
Skin


Definition

Malignant mixed tumour (MMT) is an exceedingly rare cutaneous adnexal carcinoma. It is regarded as the malignant counterpart of benign mixed tumour , but probably arises de novo, without association with its benign counterpart. MMT originates within the dermis or superficial subcutis, preferentially of trunk and extremities (particularly hands and feet). It presents as a large (2-15 cm in diameter), firm, asymmetrical, lobulated lesion with a biphasic growth pattern, infiltrative tumour margins and adjacent satellite tumour nodules. Histologically, the tumour is composed of epithelial and mesenchymal components. Epithelial tumour aggregations predominate at the periphery and present as confluent cords and nests of cells, often with interspersed zones of tubule formation. Chondromyxoid mesenchymal structures are more abundant toward the centre of the lesion. Tumour proliferation is invasive and destructive. Necrosis is common.
Malignant mixed tumour occurs in all age groups (average age 50 years) and affects women twice as often as men. Local recurrence and metastasis develops in >50% of cases; >25% of patients die. MMT metastasizes to regional lymph nodes, lung, and bone. Complete excision before metastasis is curative

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LeBoit PE, Burg G, Weedon D, Sarasin A (Eds.)
World Health Organization Classification of Tumours. Pathology and Genetics of Skin Tumours
3rd Edition
IARC Press: Lyon 2005



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