Which microscopic findings are characteristic of sarcomatoid renal cell carcinoma (SRCC)?

Updated: Mar 11, 2019
  • Author: Ronald J Cohen, MB, BCh, PhD, FRCPA, FFPATH; Chief Editor: Liang Cheng, MD  more...
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On microscopic examination, 2 main histologic types of sarcomatoid renal cell carcinoma (SRCC) have been described. A fibrosarcoma-like appearance is reported in 14-65% of cases, characterized by sheets of whorled or interlacing bundles of spindle cells. Alternately, 27-85% of cases resemble malignant fibrous histiocytoma characterized by spindle cells in a storiform pattern, a greater degree of nuclear pleomorphism, and occasional multinucleated osteoclast-like giant cells (see the image below). [7] Some tumors (3-24%) have no distinct pattern, [7] and a hemangiopericytomalike pattern has been described in rare cases. [31]

Sarcomatoid renal cell carcinoma showing a storifo Sarcomatoid renal cell carcinoma showing a storiform growth pattern (malignant fibrous histiocytoma-like) with marked nuclear pleomorphism, occasional multi-nucleated giant cells and atypical mitoses.

Histologic coagulative tumor necrosis is seen in 90% of SRCCs (see the image below), [4] while less common histologic findings include foci of myxoid stromal change and regions of chondrosarcomatous or osteosarcomatous differentiation. [17, 18]

Sarcomatoid renal cell carcinoma in a storiform pa Sarcomatoid renal cell carcinoma in a storiform pattern associated with histologic coagulative necrosis (top left).

Regions of rhabdoid differentiation are reported in around 15% of tumors classified as SRCC. [32] In 61% of SRCCs, a clear demarcation exists between the sarcomatoid and RCC components (see the image below), whereas in 39%, the 2 components are intimately admixed, often showing regions of transition between them. [7]

A region of clear demarcation between the sarcomat A region of clear demarcation between the sarcomatoid and clear cell components of sarcomatoid renal cell carcinoma.

In most cases, both the sarcomatoid (86-92%) and the RCC (67-95%) components of SRCC are of Fuhrman grade III or IV. [4, 7, 31] However, the poor prognosis associated with sarcomatoid differentiation is independent of the nuclear grade of either component, and the convention is to assign all SRCCs to Fuhrman grade IV. [4, 7, 15, 17, 33]

Ultrastructural analysis confirms the epithelial derivation of sarcomatoid components in SRCC, most commonly by revealing interdigitation of the spindle cells with occasional-to-multiple desmosomal junctions. Some tumors also have short segments of basal lamina and/or occasional cells with sparse microvilli. In SRCC with CCRCC components, the sarcomatoid cells can display small pools of glycogen and lipid. [34, 35, 36]

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