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Presented by Dr. Cimino-Mathews and prepared by Nicolas A. Giraldo-Castillo.
This case talks about a 80 year-old female with a breast mass.
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Question 1 of 1
1. Question
A 80 year-old female with a breast mass. Choose the correct diagnosis:
Correct
Answer: B. Malignant phyllodes tumor
Histology: The mass consists of a biphasic population of a bland epithelial component and an atypical stromal component. The epithelial component consists of a benign luminal cell layer with an intact myoepithelial cell layer, which line slit-like ductal spaces (“intracannalicular pattern”). The stromal cells display marked cytologic atypia including increased nuclear-to-cytoplasmic ratio, nuclear hyperchromasia, pleomorphism, and prominent nucleoli. The mitotic rate is brisk (>10 mitoses per 10 high power fields). The stromal component is expanded and meets criteria for stromal overgrowth, defined as greater than a 4X low power field composed entirely of stromal cells without an epithelial component.
Discussion: Phyllodes tumors are rare biphasic fibroepithelial neoplasms characterized by cellular stroma and leaf-like architecture, and they are subsequently subdivided into benign, borderline and malignant categories on the basis of a constellation of histologic features. These features include, 1) the tumor circumscription/degree of infiltration, 2) degree and pattern of stromal cellularity, 3) degree of stromal cell atypia, 4) stromal mitotic activity, and 5) presence or absence of malignant heterologous elements. The severity of the atypical features increase as the classification progresses from benign to borderline to malignant. The only feature that is exclusively seen in malignant phyllodes tumors is the presence of malignant heterologous element within the stroma (e.g., rhabdomyosarcomatous differentiation, chondrosarcomatous differentiation). The 2019 update to the WHO Classification of Breast Tumours, 5th Ed. made a change in the classification of malignant heterologous elements in phyllodes tumors. The presence of liposarcomatous differentiation is no longer considered a malignant heterologous element, based on evidence that areas histologically resembling liposarcomatous differentiation in phyllodes tumors do not share cytogenetic changes (e.g., MDM2 amplification) with true well-differentiated liposarcomas. Thus, “liposarcomatous-like” areas do not necessitate a diagnosis of malignancy in a phyllodes tumor.
References:
1. Tan BY, Acs G, Apple SK, et al. Phyllodes tumours of the breast: a consensus review. Histopathology. 2016 Jan;68(1):5-21.
2. Hoon Tan P, Ellis I, Allison K, et al. The 2019 WHO classification of tumours of the breast. Histopathology. 2020 Feb 13. [Epub ahead of print]Incorrect
Answer: B. Malignant phyllodes tumor
Histology: The mass consists of a biphasic population of a bland epithelial component and an atypical stromal component. The epithelial component consists of a benign luminal cell layer with an intact myoepithelial cell layer, which line slit-like ductal spaces (“intracannalicular pattern”). The stromal cells display marked cytologic atypia including increased nuclear-to-cytoplasmic ratio, nuclear hyperchromasia, pleomorphism, and prominent nucleoli. The mitotic rate is brisk (>10 mitoses per 10 high power fields). The stromal component is expanded and meets criteria for stromal overgrowth, defined as greater than a 4X low power field composed entirely of stromal cells without an epithelial component.
Discussion: Phyllodes tumors are rare biphasic fibroepithelial neoplasms characterized by cellular stroma and leaf-like architecture, and they are subsequently subdivided into benign, borderline and malignant categories on the basis of a constellation of histologic features. These features include, 1) the tumor circumscription/degree of infiltration, 2) degree and pattern of stromal cellularity, 3) degree of stromal cell atypia, 4) stromal mitotic activity, and 5) presence or absence of malignant heterologous elements. The severity of the atypical features increase as the classification progresses from benign to borderline to malignant. The only feature that is exclusively seen in malignant phyllodes tumors is the presence of malignant heterologous element within the stroma (e.g., rhabdomyosarcomatous differentiation, chondrosarcomatous differentiation). The 2019 update to the WHO Classification of Breast Tumours, 5th Ed. made a change in the classification of malignant heterologous elements in phyllodes tumors. The presence of liposarcomatous differentiation is no longer considered a malignant heterologous element, based on evidence that areas histologically resembling liposarcomatous differentiation in phyllodes tumors do not share cytogenetic changes (e.g., MDM2 amplification) with true well-differentiated liposarcomas. Thus, “liposarcomatous-like” areas do not necessitate a diagnosis of malignancy in a phyllodes tumor.
References:
1. Tan BY, Acs G, Apple SK, et al. Phyllodes tumours of the breast: a consensus review. Histopathology. 2016 Jan;68(1):5-21.
2. Hoon Tan P, Ellis I, Allison K, et al. The 2019 WHO classification of tumours of the breast. Histopathology. 2020 Feb 13. [Epub ahead of print]
