Malignant Mixed Tumor

 Glandular differentiation is often present; not as common as in benign mixed tumor of skin

image Irregular nests, cords, and sheets of cuboidal or polygonal cells

image Foci of highly atypical cells with hyperchromatic nuclei and numerous mitotic figures

• Some cases may show frankly malignant stromal cells (i.e., true carcinosarcoma)

• Infiltration of surrounding tissue, vascular invasion, and necrosis are helpful diagnostic features

• Rarely, features of associated benign mixed tumor can be seen

Top Differential Diagnoses

• Cutaneous mixed tumor

• Biphasic synovial sarcoma

MMT at Low Magnification
Malignant mixed tumor (MMT) image arising in a longstanding benign mixed tumor (well-circumscribed nodule on the left image) shows a large, asymmetrical, lobular, and infiltrative tumor invading from the dermis into the subcutaneous tissue.

MMT With Perineural Invasion
Marked infiltrative features with deep dermal and perineural image invasion is observed.

MMT at High Magnification
High magnification of an epithelial area shows infiltrative cords of cells, which demonstrate marked cytologic atypia with enlarged, hyperchromatic-staining nuclei surrounding small ductal lumina image.

HMWCK (CK5-CK6) Immunohistochemistry in MMT
The epithelial component of the tumor is strongly highlighted by a HMWCK (CK5-CK6) stain.



• Malignant mixed tumor (MMT)


• Malignant chondroid syringoma

• Malignant apocrine mixed tumor


• Rare variant of malignant tumor derived from adnexal ductal/gland and myoepithelial cells



• Most often on extremities and trunk
• More common in women

image F:M ratio ~ 2:1

• Average age at time of diagnosis is 5th decade

• Slow-growing, skin-colored tumor

• Slow protracted growth phase followed by rapid growth

• Rarely, malignant transformation from mixed tumor of skin
image Most tumors begin with anaplastic changes

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Apr 24, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Malignant Mixed Tumor

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