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Presented by William Westra, M.D. and prepared by Angelique W. Levi, M.D.
Case 1: 78 year-old woman with a submandibular mass.
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Question 1 of 1
1. Question
Week 27: Case 1
78 year-old woman with a submandibular mass. An immunostain for smooth muscle actin is included below (Image 4)./images/s-7649a.jpg
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/images/s-7649e.jpgCorrect
Answer: Carcinosarcoma (true malignant mixed tumor)
Histology: The tumor is comprised of a mixture of components reflecting divergent lines of tumor differentiation. The predominant component is seen as sheets of polygonal to spindled-shaped cells (Image 1) that diffusely infiltrate the submandibular gland and surrounding soft tissues. The cells are cytologically malignant, and mitotic figures are readily identified. Although these tumor cells are undifferentiated at the light microscopic level, they demonstrate strong cytokeratin expression by immunohistochemistry. Other components of the tumor show differentiation along mesenchymal lines. Osteosarcomatous differentiation is seen as malignant cells embedded in a mineralized osteoid-type matrix (Image 2). In addition, rounded cells with prominent pink cytoplasm resemble rhabdomyoblasts (Image 3). Indeed, these cells strongly express muscle markers by immunohistochemistry (Image 4). At the center of the tumor mass is a circumscribed zone of prominent hyalinization (Image 5).
Discussion: Among the group of salivary gland tumors known as “malignant mixed tumors” (including malignant ex-mixed tumor, metastastizing mixed tumor, and carcinosarcoma) only carcinosarcoma manifests both carcinomatous and sarcomatous components. In this example of a carcinosarcoma, the carcinomatous component is best classified as a large cell undifferentiated carcinoma. Immunohistochemical staining for cytokeratin is useful in confirming its epithelial nature and in differentiating this tumor from a pure sarcoma of salivary gland origin. The sarcomatous component of salivary gland carcinosarcomas is usually a chondrosarcoma, but a variety of other types (including osteosarcoma) have been reported. This case is exceptionally unusual for the dual occurrence of a rhabdomyosarcoma and an osteosarcoma.
Salivary gland carcinosarcomas can arise de-novo or from a pre-existing benign mixed tumor. In this case, a benign component was not identified. However, a centralized zone of prominent hyalinization suggests the likely possibilty of a pre-existing benign mixed tumor that has been overrun by its malignant component.
Incorrect
Answer: Carcinosarcoma (true malignant mixed tumor)
Histology: The tumor is comprised of a mixture of components reflecting divergent lines of tumor differentiation. The predominant component is seen as sheets of polygonal to spindled-shaped cells (Image 1) that diffusely infiltrate the submandibular gland and surrounding soft tissues. The cells are cytologically malignant, and mitotic figures are readily identified. Although these tumor cells are undifferentiated at the light microscopic level, they demonstrate strong cytokeratin expression by immunohistochemistry. Other components of the tumor show differentiation along mesenchymal lines. Osteosarcomatous differentiation is seen as malignant cells embedded in a mineralized osteoid-type matrix (Image 2). In addition, rounded cells with prominent pink cytoplasm resemble rhabdomyoblasts (Image 3). Indeed, these cells strongly express muscle markers by immunohistochemistry (Image 4). At the center of the tumor mass is a circumscribed zone of prominent hyalinization (Image 5).
Discussion: Among the group of salivary gland tumors known as “malignant mixed tumors” (including malignant ex-mixed tumor, metastastizing mixed tumor, and carcinosarcoma) only carcinosarcoma manifests both carcinomatous and sarcomatous components. In this example of a carcinosarcoma, the carcinomatous component is best classified as a large cell undifferentiated carcinoma. Immunohistochemical staining for cytokeratin is useful in confirming its epithelial nature and in differentiating this tumor from a pure sarcoma of salivary gland origin. The sarcomatous component of salivary gland carcinosarcomas is usually a chondrosarcoma, but a variety of other types (including osteosarcoma) have been reported. This case is exceptionally unusual for the dual occurrence of a rhabdomyosarcoma and an osteosarcoma.
Salivary gland carcinosarcomas can arise de-novo or from a pre-existing benign mixed tumor. In this case, a benign component was not identified. However, a centralized zone of prominent hyalinization suggests the likely possibilty of a pre-existing benign mixed tumor that has been overrun by its malignant component.
