Alpha-fetoprotein-producing transitional cell carcinoma of the urinary bladder: a case report

Urachal yolk sac tumor penetrating the bladder as a diagnostic challenge: a case report and review of the literature

Background

Yolk sac tumor (YST) is a germ cell tumor. It is primarily located in the gonads but can also occur extragonadally (extragonadal yolk sac tumor - EGYST), most commonly in the pelvis, retroperitoneum or mediastinum. Only a few YSTs of the urachus have been described.

Case report

We present a rare case report of a 37-year-old male with episodes of macroscopic hematuria. The histological specimen obtained by transurethral resection showed a solid, and in some parts papillary infiltrative, high-grade tumor with numerous areas of marked nuclear atypia and clear invasion between the detrusor bundles. Glandular pattern has been observed in only minority of the tumor. Immunohistochemistry showed significant positivity for GPC3, SALL4 and cytokeratins AE1/AE3, while KRT7 and GATA3 were negative. We concluded that the biopsy findings were consistent with urothelial carcinoma with infrequent YST differentiation. In definitive surgical specimens we found a malignant epithelial, glandular and cystically arranged tumor of germinal appearance arising from urachus. The surrounding urothelium was free of invasive or in situ tumor changes. We reclassified the tumor as a urachal YST.

Conclusion

EGYST was suspected because glandular and hepatoid structures were found, but the presence of these structures should be verified by immunohistochemistry.

Somatic-Type Yolk Sac Tumor Arising as a Predominant Component of Bladder Urothelial Carcinoma

Germ cell differentiation has been described in association with somatic tumors arising from several organ systems; rare cases arising from urothelium have been reported. Here we present a 62-year-old male with a remote history of lung cancer, a left adrenal gland mass, and a 5.6 cm left bladder wall mass; cystoscopy demonstrated a large papillary mass on the left anterior bladder wall. A transurethral resection specimen was sent for review in consultation and showed extensive papillary structures with thin fibrovascular cores lined by neoplastic cells with clear cytoplasm. These neoplastic cells were diffusely positive for pancytokeratin, CDX2 (caudal-type homebox 2), SALL4 (sal-like transcription factor 4), glypican-3, AFP (alpha-fetoprotein), while negative for PAX-8 (paired box gene 8), NKX3.1 (NK3 homeobox 1), PSA (prostate specific antigen), TTF-1 (thyroid transcription factor 1), Napsin A, inhibin, and OCT4 (octamer-binding transcription factor 4). Conventional urothelial conventional carcinoma and focal squamous differentiation were also identified as minor components. Urothelial carcinoma was focally positive for GATA3 (GATA-binding protein 3) and p63; SALL4 and glypican-3 were negative. Overall findings supported a yolk sac tumor with a smaller component of squamous cell carcinoma (<1%). Subsequent cystectomy showed similar morphologic features and immunoprofile in addition to foci of urothelial carcinoma and urothelial carcinoma in situ. No chromosome 12p abnormalities were identified by fluorescent in-situ hybridization study. A diagnosis of yolk sac tumor derived from urothelial carcinoma was made. Yolk sac tumor should be considered in the differential diagnosis of a high-grade urothelial carcinoma, particularly when glandular or other unusual architectural patterns are present. A somatic origin with underlying genomic instability similar to what has been described in the uterus and ovaries is suggested.