[833] The Role of Immunohistochemistry (IHC) in the Differential Diagnosis of Invasive Plasmacytoid Urothelial Carcinoma (PUC) and Its Mimics

Kristin L Dishongh, Jesse K McKenney, Ankur R Sangoi, Neriman Gokden. University of Arkansas for Medical Sciences, Little Rock, AR; Stanford University School of Medicine, Stanford, CA; El Camino Hospital, Mountain View, CA

Background: PUC is a rare and aggressive variant of bladder cancer that is characterized by tumor cells closely resembling plasma cells. PUC may mimic plasmacytoma, lymphomas, and carcinomas such as lobular carcinoma of breast (LCB) and poorly differentiated carcinomas of gastrointestinal system (PDCGIS) secondarily involving the bladder. There is limited data regarding the comparative immunophenotypes of these morphologically similar tumors.
Design: The surgical pathology and consultation files at three institutions were searched for PUC, LCB and PDCGIS from 1998 to 2010. H&E slides of 31 cases were reviewed to confirm diagnoses. A focused IHC panel including E-Cadherin, P63, P53, CD138, MUM-1, estrogen receptor (ER), progesterone receptor (PR), GCDFP-15, CEA 125, cytokeratin 7 (CK 7), and cytokeratin 20 (CK 20) was performed. Percent immunoreactivity in the neoplastic cells was graded as 1 to 4+.
Results: PUC (n=11) showed immunoreactivity for CD138 and P53, but were negative for MUM-1, ER, PR, and GCDFP-15 in all cases. E-Cadherin expression was completely lost in 25% of cases, and nuclear P63 was not expressed in 55% of cases. 99% had CK7 expression while 73% expressed CK20. LCB (n=10) were immunoreactive for ER (100%), PR (60%), GCDFP-15 (90%), CK 7 (100%), P53 (60%), CD 138 (100%), CEA 125 (20%), but negative for MUM-1, P63, E-cad, and CK 20 in all cases. PDCGIS (n=10) were immunoreactive for CD138 and E-cad, but negative for ER, PR and GCDFP-15 in all cases. Other variably positive markers in PDCGIS included P53 (90%), P63 (30%), CEA125 (10%), CK 7 (60%), and CK 20 (80%).
Conclusions: It is important to recognize PUC because it is an aggressive bladder cancer variant with poor prognosis that presents at an advanced clinical stage. Particularly in small samples, the distinction from morphologically similar plasmacytomas/lymphomas or carcinomas from other anatomic sites may be difficult. The typical immunoprofile of PUC is CD138 (+), CK7/20 (+), and MUM-1 (-), ER/PR/GCDFP-15 (-).The absence of MUM-1 staining in PUC would be helpful in the distinction from plasma cells and lymphocytes. PDCGIS has a variable immunoprofile which overlaps significantly with PUC. P63 and E-cad expression in a subset of PUC and ER, PR and GCDFP-15 negativity is useful in distinction from LCB.
Category: Genitourinary (including renal tumors)

Tuesday, March 20, 2012 1:00 PM

Poster Session IV # 82, Tuesday Afternoon


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