The vast majority of malignant urachal epithelial
tumors have a glandular morphology (ie,
adenocarcinoma), to which our principal understanding of
urachal carcinoma and its prevailing set of diagnostic criteria are largely ascribed. The 2004 World Health Organization classification of genitourinary
tumors recognizes other rarer histologic types of urachal
carcinomas such as urothelial, squamous cell, and other
carcinomas. However, the clinicopathologic data for these nonglandular groups of urachal
carcinomas are very limited, being detailed only in sporadic case reports. Some of the criteria recommended for pathologic confirmation of urachal
carcinomas were formulated almost exclusively for
urachal adenocarcinoma and may not be relevant or applicable for nonglandular
tumors. Here, we present 7 examples of pure (5) and mixed predominant (2) nonglandular urachal
carcinomas. Patients were 45 to 85 years of age (mean, 64.1) with a male predominance (male-to-female ratio=6:1). Six
tumors were related to the bladder [dome (3) or dome/supravesical (3)] and 1 was entirely supravesical. Histologically, 5 were urothelial
carcinomas, of pure or mixed histology, all were high grade and invasive, and 2 were
small cell carcinomas. Two urothelial
carcinomas had focal (<5%) glandular differentiation and signet ring cell change, and 1 had admixed focal malignant squamous cells and high-grade dedifferentiated components. Four of 5 urachal urothelial
carcinomas exhibited solid and partly cavitary or
luminal growth with papillary structures and a variable amount of
necrosis within the cavity. The 2
small cell carcinomas were pure, had classic undifferentiated neuroendocrine histology, were situated at the bladder dome, and were partly cavitary filled with necrotic debris. Urachal remnant was identified in 6
tumors mainly with dysplastic transitional cells in the urachal canal or rudimentary nests and tubules. All 6 bladder-related urachal
tumors exhibited reverse invasive front from the surface, including 2
tumors that ulcerated the bladder mucosa. One
tumor had concomitant in situ and noninvasive high-grade papillary urothelial
carcinomas in the main bladder lumen. Sheldon stages at presentation were IIIA (2), IVA (3), and IVB (2). Follow-up in all 7 cases (<1 to 60 mo; median, 12.5 mo) showed that 6 patients had died of disease, including the 2 patients with
small cell carcinoma. In conclusion, nonglandular
urachal carcinoma may occur with pure histology or admixed with high-grade dedifferentiated morphologies and a minor
adenocarcinoma component. These
tumors may arise as deep-seated bladder-related or completely supravesical
tumors along the urachal tract and may exhibit reverse invasive spread toward the bladder surface. Cavitary or
luminal growth may occur that could be attributed to the intraurachal neoplastic proliferation. Urachal urothelial
carcinomas in particular may contain papillary structures within the
tumor and urachal cavity. Concomitant primary urothelial
carcinoma outside of the urachus and
tumor extension to bladder mucosa may occur, which should not negate diagnosis of an urachal primary. Behavior appears poor, as most
tumors present with higher stage.