115th Annual Meeting of the United-States-and-Canadian-Academy-of-Pathology (USCAP), San-Antonio, Kuzey Mariana Adaları, 21 - 26 Mart 2026, cilt.106, (Özet Bildiri)
Eosinophilic vacuolated tumor (EVT) is an emerging renal oncocytic tumor in the 2022 World Health Organization classification. Prototypical morphologic features include eosinophilic cytoplasm with large, optically clear vacuoles and enlarged nuclei with prominent nucleoli. However, its immunoprofile, characterized by positivity for CD117, cathepsin K, CD10 and GPNMB with variable KRT7/KRT20 expression, overlaps with other entities in the morphological differential diagnosis. We have anecdotally noted that EVTs are often positive for CD56, and herein explore the diagnostic sensitivity and specificity of CD56 in a large cohort of eosinophilic renal neoplasms including EVT.
Design
A cohort of EVTs (n=40) and other eosinophilic kidney tumors (n=115) collected from 16 institutions were stained for CD56 and semi-quantitively scored as follows: 0 (≤2%), 1+ (2-10%), 2+ (10-50%), or 3+ (>50%). All diagnoses were made by genitourinary pathologists with the aid of immunohistochemical studies. Clinicopathologic features were recorded for EVTs including MTOR/TSC1/TSC2 status when available.
Results
The median age of EVT patients was 51 years (range 13-80 years). The M:F ratio was 1:1.7. EVT specimens were: biopsy (n=5), partial nephrectomy (n=24), and radical nephrectomy (n=11). Next generation sequencing detected a MTOR/TSC1/TSC2 variant in 11/13 EVTs. CD56 expression was found in 38/40 (95%) EVTs. Most EVTs (n=33/40, 82.5%) had 3+/diffuse CD56 expression (Figure 1) and this pattern of reactivity was found to be the most specific for EVT (Table 1). However, a 3+ pattern of CD56 expression was also seen in 12/35 (34.3%) oncocytomas, 1/20 (5%) eosinophilic solid and cystic (ESC) renal cell carcinomas (RCC), and 2/4 hybrid oncocytic tumors (Figure 2). Eosinophilic chromophobe RCC (n=11), eosinophilic clear cell RCC (n=7), SDH-deficient RCC (n=5), epithelioid angiomyolipoma (n=7), low grade oncocytic tumor (n=23), and urothelial carcinoma (n=5) were all/mostly negative for CD56, with rare cases showing at most a 1+ staining pattern.
CD56 positivity criteria
Sensitivity
Specificity
1+/2+/3+ expression
95.0% (38/40)
73.9% (85/115)
2+/3+ expression
90.0% (36/40)
78.3% (90/115)
3+ expression
82.5% (33/40)
87.0% (100/115)
Table 1
Sensitivity and specificity of CD56 for eosinophilic vacuolated tumor using different percent cut-offs to define CD56 positivity
Our findings support the utility of CD56 as an adjunct diagnostic tool in the workup of kidney tumors (along with CD117, cathepsin K, GPNMB, KRT7, KRT20, SDHB, and CD10) when EVT is a consideration in the differential diagnosis. Diffuse CD56 showed high sensitivity and moderate specificity for EVT. Importantly, the presence of diffuse CD56 excluded most types of RCC except a small subset of ESC RCC.
