Which microscopic findings are characteristic of rhabdoid renal cell carcinoma (RRCC)?

Updated: Mar 11, 2019
  • Author: Ronald J Cohen, MB, BCh, PhD, FRCPA, FFPATH; Chief Editor: Liang Cheng, MD  more...
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Answer

On microscopic examination, the rhabdoid component of rhabdoid renal cell carcinoma (RRCC) is characterized by large round or polygonal cells with globular eosinophilic paranuclear inclusion bodies, large eccentric vesicular nuclei, prominent nucleoli, and abundant eosinophilic cytoplasm (see the image below). [8, 9, 10, 11] A variable proportion of these large pleomorphic cells may lack inclusion bodies, and some have clear cytoplasm, which is due in some cases to glycogen deposits [9] and in other cases to coalescence of large vacuoles in the cell periphery. [8]

Rhabdoid renal cell carcinoma showing large pleomo Rhabdoid renal cell carcinoma showing large pleomorphic cells with globular eosinophilic paranuclear inclusion bodies, large eccentric vesicular nuclei, prominent nucleoli and abundant eosinophilic cytoplasm. Note lymphocytic infiltrate.

The 2 main architectural growth patterns reported are solid sheets of cells or an alveolar pattern with delicate fibrovascular septae encircling solid nests of cells. Stroma is scanty, with occasional cases showing stromal myxoid change or hyalinization.

The rhabdoid components are commonly associated with hemorrhage (39% of cases), necrosis (22%), and focal lymphocytic infiltration. A coexisting sarcomatoid component is reported in 7-50% of RRCCs, often showing transition with rhabdoid components and occasionally intermixed with the rhabdoid cells. [8, 9, 10, 11]

In most RRCCs, the rhabdoid component also shows transition with coexisting RCC components, although in some tumors, these 2 morphologic elements are distinct and separated by a fibrous capsule. [9, 10]

In rare cases, no RCC component is detected despite extensive sampling of the tumor. [9, 12] In most RRCCs (86-94%), the RCC components are of Fuhrman grade III or IV, and the rhabdoid cells are typically described as high grade. [8, 11] Given the poor prognosis associated with this form of differentiation, rhabdoid change should likely be viewed as analogous to sarcomatoid change, and all RRCCs should be assigned to Fuhrman grade IV.

Ultrastructural analysis shows that 43-50% of RRCCs have classic rhabdoid cells with eccentric nuclei displaced by paranuclear cytoplasmic condensations of intermediate filaments, often in a concentric whorled pattern. [8, 10] Although rhabdoid cells in the remaining cases do contain increased amounts of intermediate filaments, the cytoplasmic inclusion bodies visible by light microscopy are due to paranuclear aggregation of organelles that have been displaced by large vacuoles in the cell periphery. [8] Similar findings have been reported in some cases of pediatric MRT of the kidney, in which the vacuoles were interpreted as large dilated cisternae of endoplasmic reticulum. [37]


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