PMC5515098_01
Noncontrast CT coronal image. There is a 6 cm mixed solid and cystic lesion arising from the native left lower renal pole (white arrow) with an adjacent medial 1.8 cm soft tissue nodule (black arrow).
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Noncontrast abdominopelvic CT scan revealed a 6 cm mixed solid and cystic left lower pole lesion arising from the native left kidney, as well as an adjacent 1.8 cm soft tissue nodule (Fig. 1).
Gross specimen sectioning revealed a circumscribed mass with a central scar and granular texture (white arrow). A portion of the mass was distinct with a smooth texture and white appearance (black arrow).
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Sections of the kidney mass identified a collision of two neoplasms with different morphologies (Fig. 2).
Histomorphology: (A) clear cell RCC, seen as nests of neoplastic cells with optically clear cytoplasm, set in a delicate vascular network. (B) Immunohistochemistry for CA-IX highlights strong membranous expression, corroborating the diagnosis of clear cell RCC. (C) High-grade B cell lymphoma, seen as discohesive neoplastic cells with moderate to scant cytoplasm and large nuclei with prominent nucleoli. (D) Immunohistochemistry for PAX-5 highlights nuclear expression, corroborating the B cell phenotype of neoplastic cells. RCC = renal cell carcinoma; CA-IX = carbonic anhydrase-IX; PAX-5 = paired box (PAX) family.
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The first mass measured 3.5 cm and was composed of nests of tumor cells with optically clear cytoplasm, set within a delicate vascular network (Fig. 3A). Immunohistochemistry on this part showed tumor cells positive for CA-IX and PAX-8, corroborating the morphologic impression of classic clear cell RCC (Fig. 3B). The larger second mass measured 8.1 cm and consisted of sheets of monomorphic tumor cells with moderate to scant cytoplasm and enlarged nuclei with prominent nucleoli (Fig. 3C). Immunohistochemistry on this part showed tumor cells negative for CA-IX and positive for PAX-5, CD45, MUM1, and MYC (Fig. 3D).