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Presented by Dr. Jonathan Epstein and prepared by Dr. J. Judd Fite.
Case 3. A 65 year old man underwent a nephrectomy for a renal mass. Atypical mitotic figures were noted upon histological examination.
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Question 1 of 1
1. Question
A 65 year old man underwent a nephrectomy for a renal mass. Atypical mitotic figures were noted upon histological examination.
Correct
Answer: C. Malignant epithelioid angiomyolipoma
Histological Description: The tumor is composed of epithelioid cells with an overall high N/C with variable amount of pale clear to eosinophilic cytoplasm. Some are pleomorphic cells with multinucleation around the perimeter of the cell, and abundant cytoplasm termed “amoeboid cells”. Areas of necrosis are present. Mitotic figures are not frequent. The lesion lacks areas of usual angiomyolipoma.
Discussion: Angiomyolipomas (AML) is more frequently sporadic but can also be seen associated with tuberous sclerosis (TS). In patients with TS, presentation is at a younger age and lesions are multifocal and bilateral. AMLs can be epithelioid with and without atypia. In cases where the cells have a more epithelial appearance as opposed to spindled, yet there is no atypia, then these lesions are entirely benign. In cases with both epithelioid morphology and atypia there is a risk of malignant behavior. In our prior study we found the following criteria to be helpful to predict malignancy in these lesions, which in one third of cases, there is recurrence and metastases. Malignant behavior correlated with presence of 3 of the 4 following features: 1) >70% atypical epithelioid areas; 2) >2 mitoses per 10 HPF; 3) atypical mitotic figures; or 4) necrosis. In the current case all of the tumor has atypical epithelioid features, along with necrosis and atypical mitotic figures so the diagnosis was malignant epithelioid AML. In order to distinguish from a high grade renal cell carcinoma immunohistochemistry can be utilized. Typically positive these AMLs are positive for HMB45 and Melan A. In some negative cases, Cathepsin K is positive. Cytokeratins and PAX8 are negative, in contrast to what is seen in renal cell carcinoma.
Incorrect
Answer: C. Malignant epithelioid angiomyolipoma
Histological Description: The tumor is composed of epithelioid cells with an overall high N/C with variable amount of pale clear to eosinophilic cytoplasm. Some are pleomorphic cells with multinucleation around the perimeter of the cell, and abundant cytoplasm termed “amoeboid cells”. Areas of necrosis are present. Mitotic figures are not frequent. The lesion lacks areas of usual angiomyolipoma.
Discussion: Angiomyolipomas (AML) is more frequently sporadic but can also be seen associated with tuberous sclerosis (TS). In patients with TS, presentation is at a younger age and lesions are multifocal and bilateral. AMLs can be epithelioid with and without atypia. In cases where the cells have a more epithelial appearance as opposed to spindled, yet there is no atypia, then these lesions are entirely benign. In cases with both epithelioid morphology and atypia there is a risk of malignant behavior. In our prior study we found the following criteria to be helpful to predict malignancy in these lesions, which in one third of cases, there is recurrence and metastases. Malignant behavior correlated with presence of 3 of the 4 following features: 1) >70% atypical epithelioid areas; 2) >2 mitoses per 10 HPF; 3) atypical mitotic figures; or 4) necrosis. In the current case all of the tumor has atypical epithelioid features, along with necrosis and atypical mitotic figures so the diagnosis was malignant epithelioid AML. In order to distinguish from a high grade renal cell carcinoma immunohistochemistry can be utilized. Typically positive these AMLs are positive for HMB45 and Melan A. In some negative cases, Cathepsin K is positive. Cytokeratins and PAX8 are negative, in contrast to what is seen in renal cell carcinoma.
