COW-2020-11

CASE OF THE WEEK

2020-11 / MARCH 17
(CONTRIBUTOR: CONSTANTINA PETRAKI)

71 y/o male with an incidental 4.8 cm renal tumor treated with partial nephrectomy. The tumour is positive for PAX8, CK7 and KSP-Cadherin. CK20, Vimentin, CD10, AMACR and CA IX are negative. SDHB and Fumarate Hydratase are retained. The Ki-67/MIB1 index is low (≤5%).

Quiz

1. What is the correct diagnosis?

a. Oncocytoma

b. Eosinophylic variant of chromophobe renal cell carcinoma

c. Hybrid oncocytoma-chromophobe tumor (HOCT)

d. Low-grade oncocytic tumor (LOT)

e. Clear cell renal cell carcinoma with eosinophilic changes

1. Low-grade oncocytic tumor (LOT)

Pictures show an oncocytic neoplasm with round to oval nuclei with mostly no perinuclear halo.
Low-grade oncocytic tumor of the kidney is a recently described neoplasm with distinct morphology and immunophenotype (CK7+, CD117-) as well as with indolent behavior. A readily recognizable morphology includes solid growth pattern and sharply delineated oedematous hypocellular stromal areas with loosely arranged tumor cells, some with myoid-cell like morphology and others exhibiting cords, trabeculae or loose reticular growth. Focal fresh haemorrhage and lymphocytic clusters are often seen. The differential diagnosis includes oncocytoma, eosinophylic variant of chromophobe renal cell carcinoma, HOCT and eosinophilic variant of clear cell renal cell carcinoma.

Trpkov K, Williamson SR, Gao Y, et al. Low-grade oncocytic tumour of kidney (CD117-negative, cytokeratin 7-positive): a distinct entity?
Histopathology 2019 ,75: 174–184.

Constantina Petraki
Metropolitan Hospital, Athens, Greece
constantinapetraki@gmail.com

Kidney

oncocytic, low grade