What appears at first glance to be a renal vascular tumor may in fact be a rare type of renal cell carcinoma (RCC), authors of a case study cautioned.
A tumor recovered from a 62-year old woman who underwent a partial nephrectomy for an incidentally discovered asymptomatic left renal mass contained arborizing vessels that mimicked hemangioma. Immunohistochemical staining of the tumor highlighted the vascular component but masked epithelial cells, a situation that, in the absence of other clues, might cause a misdiagnosis, reported Kanika Taneja, MD, from the Henry Ford Cancer Institute in Detroit, and her colleagues.
The authors were tipped off to an unusual presentation, however, by mixed signals from immunohistochemical staining, leading them to an admittedly fuzzy diagnosis of “unclassified hemangioma-like RCC.”
“This case highlights that renal cell carcinoma must be strongly considered in the differential diagnosis of renal vascular tumors, and broadens the spectrum of histologies that may mimic hemangioma,” they wrote in Human Pathology.
Although there are a few recent reports in the medical literature of clear cell RCC tumors that mimic hemangiomas, the authors noted that, “to our knowledge, non–clear cell hemangioma-like renal cell carcinoma has not been previously reported.”
The tumor in question was removed from the patient with clear surgical margins during a partial nephrectomy.
Gross examination showed a 2.6 by 2.5 by 2.5 cm, well-circumscribed, tan-brown hemorrhagic mass. On microscopic examination the tumor had hemangioma-like features and lacked typical clear cell morphology, and immunohistochemical staining did little to clarify the picture.
Specifically, although staining highlighted the epithelial component of the tumor, the investigators saw what they described as “an abnormal combination of positive markers” that are normally used to distinguish clear cell from papillary histologies, effectively throwing a monkey wrench into the diagnostic works.
The marker profile in this case included cytokeratin 7, high molecular weight cytokeratin, and carbonic anhydrase IX, but only minimal labeling for alpha-methylacyl-CoA racemase and absence of GATA3.
To add to the confusion, fluorescent in situ hybridization “revealed negative studies for chromosome 3p, trisomy 7 or 17, and MITF family translocations, failing to further place this unique neoplasm into a definitive category,” Dr. Taneja and her colleagues wrote, adding that further study of the tumor may help to clarify whether it represents a distinct tumor type or is simply an unusual pattern caused by degeneration and involution of a known tumor type.
The authors did not disclose a study funding source, but reported having no conflicts of interest.
SOURCE: Taneja K et al. Hum Pathol. 2017 Nov 2. doi: 10.1016/j.humpath.2017.09.015.