Clinically undetected plasmacytoid urothelial carcinoma of the urinary bladder with non-mass-forming metastases in multiple organs: an autopsy case

Abstract

This case report outlines a clinically undetected urinary bladder plasmacytoid urothelial carcinoma (PUC) with multiple metastases detected at autopsy. An 89-year-old man presented with edema in the lower limbs. Pleural fluid cytology revealed discohesive carcinomatous cells, although imaging studies failed to identify the primary site of tumor. The patient died of respiratory failure. Autopsy disclosed a prostate tumor and diffusely thickened urinary bladder and rectum without distinct tumorous lesions. Histologically, the tumor consisted of acinar-type prostate adenocarcinoma with no signs of metastasis. Additionally, small, plasmacytoid tumor cells were observed in the urinary bladder/rectum as isolated or small clustering fashions. These metastasized to the lungs, intestine, generalized lymph nodes in a non-mass-forming manner. Combined with immunohistochemical studies, these tumor cells were diagnosed PUC derived from the urinary bladder. Both clinicians and pathologists should recognize PUC as an aggressive histological variant, which can represent a rapid systemic progression without mass-forming lesions.

Keywords: Autopsy; Cancer of unknown primary; Plasmacytoid variant; Urinary bladder; Urothelial carcinoma.

Fig. 1

Premortem microscopic findings. (A) Transurethral resection specimen showing urothelial carcinoma in situ with a stromal microinvasion. (B) Discohesive carcinomatous cells with signet-ring or plasmacytoid features in the cell block from pleural fluid was noted. Gross examination at autopsy. (C) Anterior view of the gross description of the pelvic organs. (D) A prostate tumor protruding into the urethra is detected (arrowheads). Around this tumor, the rectal wall and posterior wall of the urinary bladder are diffusely thickened.

Fig. 2

Microscopic findings. (A, B) The thickened lesion in the urinary bladder wall, showing diffuse infiltration of discohesive, plasmacytoid tumor cells in a single file pattern and small nests in the edematous lamina propria (A) and muscularis propria (B). (C) The plasmacytoid tumor cells consisted of oval-to-round, eccentrically located nuclei and abundant densely eosinophilic and occasionally vacuolated/signet-ring-cell like cytoplasm. (D) Massive tumor extension into the thickened rectal wall, seminal vesicles, and periprostatic tissue (arrows) close to the prostate cancer (arrowheads) is observed. (E, F) Diffuse positive immunoreactivity for GATA binding protein 3 (E) and negative immunoreactivity for NK3 homeobox1 (F) in the plasmacytoid tumor cells (arrows, both E and F), and vice versa, in the prostate cancer cells (arrowheads, both E and F) is observed.

Fig. 3

(A) Retained immunoreactivity for E-cadherin and moderate-intensity immunoreactivity for human epidermal growth factor receptor 2 (HER2) were noted in cancer cells. (B) Fluorescence in situ hybridization for the copy number of HER2 gene showing no HER2 amplification in cancer cells. DAPI-counterstained interphase nuclei are observed; the red and green signals indicate the HER2 and CEP17 signals, respectively. (C) Metastatic small clusters or isolated cancer cells in the lungs. (D) Immunostaining for D2-40 highlighting lymphatic invasion of cancer cells. (E) Metastatic cancer cells in the sacral bone marrow.