case_images: PMC5771372_01
case_images: Maximum intensity projection (MIP) images in anterior and posterior views of the 18F-FDG PET/CT images showing multiple hypermetabolic foci of increased FDG uptake throughout the body, most likely representing widespread metastatic disease.
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case_images: The study showed multiple hypermetabolic foci throughout the body (Figure 1).
case_images: Axial 18F-FDG PET/CT fusion images. Foci of markedly increased 18F-FDG uptake are shown in the peritoneal cavity, and in exophytic lesions in the kidneys bilaterally.
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case_images: Both kidneys contained exophytic lesions with increased 18F-FDG uptake (Figure 2).
case_images: A diagnostic challenge. (A) On hematoxylin-eosin staining, this excisional biopsy demonstrates a lymph node that has been entirely replaced by a high-grade, eosinophilic, homogeneously sarcomatoid malignancy with no evidence of differentiation. There is a high degree of both cellular atypia, ranging from spindled cells to fried egg cells, and nuclear atypia, featuring vesicular chromatin, irregular nuclear borders, and prominent nucleoli. A portion of this tissue was sent for flow cytometry prior to microscopic analysis, which excluded a hematologic malignancy, as no significant lymphoid population was identified. (B) Immunostaining to identify the tissue of origin for this malignancy demonstrated tumor cell nonreactivity for cytokeratins 7 and 20, with reactivity for vimentin and PAX8. These immunohistochemical and morphological findings are most consistent with a high-grade sarcomatoid carcinoma of renal origin. (C) Interrogation of prognostic/predictive markers by immunohistochemistry demonstrated high PD-L1 expression levels and was negative for BRAF V600E hotspot mutation. Fluorescence In Situ Hybridization studies with break-apart probes were negative for rearrangements in ALK and ROS1, suggesting that this patient might benefit from treatment with pembrolizumab and would be less likely to benefit from treatment with crizotinib and dabrafenib.
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case_images: The rare hematologic cells that were identified represented a small population of tumor infiltrating T-cells, a common phenomenon. The remaining portion was sent for histologic analysis, and was found to be a high-grade sarcomatoid carcinoma with no evidence of differentiation (Figure 3A). After correlation with the imaging studies, which identified bilateral, FDG-avid, exophytic lesions in the kidneys, a final diagnosis of sarcomatoid carcinoma of renal origin was rendered (Figure 3B).