Low‐grade oncocytic tumour of kidney (CD117‐negative, cytokeratin 7‐positive): a distinct entity?

Abstract

Aim To describe a group of distinct low‐grade oncocytic renal tumours that demonstrate CD117 negative/cytokeratin (CK) 7‐positive immunoprofile. Methods and results We identified 28 such tumours from four large renal tumour archives. We performed immunohistochemistry for: CK7, CD117, PAX8, CD10, AMACR, e‐cadherin, CK20, CA9, AE1/AE3, vimentin, BerEP4, MOC31, CK5/6, p63, HMB45, melan A, CD15 and FH. In 14 cases we performed array CGH, with a successful result in nine cases. Median patient age was 66 years (range 49–78 years) with a male‐to‐female ratio of 1:1.8. Median tumour size was 3 cm (range 1.1–13.5 cm). All were single tumours, solid and tan‐brown, without a syndromic association. On microscopy, all cases showed solid and compact nested growth. There were frequent areas of oedematous stroma with loosely arranged cells. The tumour cells had oncocytic cytoplasm with uniformly round to oval nuclei, but without significant irregularities, and showed only focal perinuclear halos. Negative CD117 and positive CK7 reactivity were present in all cases (in two cases there was focal and very weak CD117 reactivity). Uniform reactivity was found for PAX8, AE1/AE3, e‐cadherin, BerEP4 and MOC31. Negative stains included CA9, CK20, vimentin, CK5/6, p63, HMB45, Melan A and CD15. CD10 and AMACR were either negative or focally positive; FH was retained. On array CGH, there were frequent deletions at 19p13.3 (seven of nine), 1p36.33 (five of nine) and 19q13.11 (four of nine); disomic status was found in two of nine cases. On follow‐up (mean 31.8 months, range 1–118), all patients were alive with no disease progression. Conclusion Low‐grade oncocytic tumours that are CD117‐negative/CK7‐positive demonstrate consistent and readily recognisable morphology, immunoprofile and indolent behaviour.

ESC, ALK, HOT and LOT: Three Letter Acronyms of Emerging Renal Entities Knocking on the Door of the WHO Classification

“…LOT is typically a single and sporadic tumor, found in a non-syndromic setting and in older patients (median age 66 years). There is a female predilection (M:F = 1:1.8) [44]. During the follow-up, these tumors behaved indolently, with no evidence of disease progression, although this is based on a single study with a relatively limited follow-up (mean 31.8 months) [44].…”

“…LOT is typically a single, small tumor that shows low stage and, based on the available data, it exhibits an indolent clinical behavior [44]. The awareness of the constellation of the clinical, morphologic and immunophenotypic features of this tumor that we provisionally named "LOT" will hopefully increase its recognition and will prompt re-evaluation of similar oncocytic tumors that were diagnosed using various terms.…”

“…Low-grade oncocytic tumor (LOT) has been recently proposed as a distinct renal entity, emerging from the spectrum of oncocytic renal tumors that are difficult to classify [44]. In the only published study to date, consisting of 28 cases collected from four large institutional renal tumor archives, LOT showed fairy consistent morphologic features and immunoprofile characterized by lack of CD117 reactivity and diffuse positivity for CK7 [44]. Although LOT demonstrates an overlapping morphology with renal oncocytoma and eosinophilic Chr RCC, it does not fit completely into either of these entities.…”

Eosinophilic Kidney Tumors: Old and New

“…Staining with cytokeratin (CK) 7 and a-methylacyl CoA racemase/P504s (AMACR) can rule out papillary carcinoma, and cluster of differentiation (CD) 117 can be useful in ruling out chromophobe RCC and oncocytoma. 5 If the growth pattern is papillary with macrophages in stromal cores, the oncocytic variant of papillary RCC may be considered. 6,7 Histologically, there are 2 types of papillary RCC: type 1 and type 2.…”

“…Papillary RCC is also positive for CD10 and negative for CD117, which is helpful for ruling out oncocytoma. 5,7 Morphologically, oncocytomas may have a papillary pattern, but lack stromal cores showing blood vessels, red blood cells, and macrophages. When considering collecting duct/medullary carcinoma, CK34bE12 is generally positive, but it is usually negative in papillary carcinoma.…”