Bladder Dome Lesion in a Man

Deloar Hossain, M.D.

Specimen Type:

Urachus

History:

A 48-year-old man presented with a mass in the umbilical region.

Pathologic Features:

Clinically, a cystic lesion was found arising from the dome of the bladder. Grossly, the cyst measuring 3.5 cm in greatest dimention is filled with a yellow, greasy, and slightly turbid liquid. The inner surface of the cyst wall is trabeculated, tan, delicately vasularized with a single focus of yellow thickening and discoloration (1.0 cm in greatest dimention). No additional mass or lesion is identified. Representative sections are submitted in 5 blocks.

Microscopic sections demonstrate an urachal cyst arising from an urachal remnant. The cyst is lined for the most part by a flat epithelial lining characterized by a single layer of glandular epithelium (Fig 1, 2). Focally this flat epithelium is replaced with small papillae lined by short columnar epithelium (Fig 3, 4) as well as urothelium (Fig 5, 6). The lesion is exophytic into the cyst lumen without any evidence of invasion into the underlying smooth muscle of the cyst wall (Fig 3, 4, 5). The lining cells display no cytological atypia (Fig 7).

Differential Diagnosis:

  • Adenocarcinoma arising from urachal cyst
  • Urachal cystadenoma

Adenocarcinoma associated with urachal cyst: This is an extraordinary rare lesion, with only few documented cases (references 1, 2). Grossly, the cyst is usually unilocular and filled with mucin. Histologically, the cyst is lined by mucinous epithelium with papillary projections into the cavity. The epithelium displays marked cytological atypia at least focally. Invasion into stroma may or may not be present. Association with pseudomyxoma peritonei is frequently seen.

Urachal cystadenoma: This is also an extraordinary rare lesion, with only few cases reported in the literature (reference 3). Grossly, the cystic lesion is unilocular or multilocular, and filled with abundant mucin. Histologically, the cyst is lined by mucinous epithelium with basally located nuclei and an absence of cytological atypia (Fig 8, 9). Papillary projections into the cyst lumen can be identified (Fig 10), but are not necessarily required for the diagnosis. Stromal invasion should not be present.

Diagnosis:

Urachal cyst with focal benign micropapillary proliferation

Key Fearures:

  • Cystic lesion characterized by flat to columnar non-mucinous epithelium or urothelium
  • Bland cytological features, no stromal invasion
  • Papillary proliferation lined by epithelium similar to non-papillary areas

Comment: Urachal cyst is not uncommon and can occur at any level of the urachus. The unusual feature in this case is the presence of papillary structures that raises the concern for adenocarcinoma or cystadenoma. Lack of cytological atypia and/or stromal invasion excludes the possibility of malignancy (adenocarcinoma). Absence of uniform proferative mucinous epithelium characteristic of cystadenoma, also argues against this consideration. Despite the papillary proliferation, the lining epithelium in this case is no different than that in common urachal cyst.

References:

  1. Sasano H, Shizawa S, Nagura H, Yamaki T. Mucinous adenocarcinoma arising in a giant urachal cyst associated with pseudomyxoma peritonei and stromal osseous metaplasia. Pathol Int. 1997 Jul;47(7):502-5.
  2. Stenhouse G, McRae D, Pollock AM. Urachal adenocarcinoma in situ with pseudomyxoma peritonei: a case report. J Clin Pathol. 2003 Feb;56(2):152-3.
  3. Hull MT, Warfel KA. Urachal cystadenoma with abundant glycogen: ultrastructural study. Ultrastruct Pathol. 1994 Sep-Oct;18(5):499-502.