Primary adenocarcinoma of the bladder is rare, accounting for only 2% or less of malignant bladder tumours.3, 4, 7–9, 13
It may show a variety of histopathological glandular patterns,13–15
but is often mucin secreting, and may present with mucousuria. There are two commonly proposed mechanisms for the development of primary bladder adenocarcinoma. One involves the malignant transformation of metaplastic intestinal-type epithelium associated with a condition known as cystitis glandularis. Such tumours are located most commonly in the vicinity of the trigone. The second mechanism invokes neoplastic transformation of the glandular epithelium lining the intravesical portion of the urachal remnants. Accordingly, this neoplasm is usually found in the dome and anterior wall of the bladder. Either of the two proposed mechanisms may give rise to a villous adenoma similar to that of the colon.3, 4, 7–9
In addition, both non-invasive and invasive adenocarcinomas arising in association with villous adenoma attest to the malignant potential of adenoma. Here, we present morphological evidence that malignant transformation of villous adenoma, an accepted mechanism for the development of adenocarcinoma of the colon, accounts for the histogenesis of some primary adenocarcinomas of the bladder.
In general, the prognosis of such cases, including villous adenoma, is very good. However, it may depend on the presence of peritoneal implants and on the resection margin status.
“Urinary mucous is a common and relatively specific symptom for adenomas of the lower urachus”
Resection alone is effective treatment but care must be exercised to avoid spilling adenoma/carcinoma cells in the peritoneum and to remove the lesion with ample free margins. Our patient showed peritoneal implants. This was probably because the peritoneal surface of the lesions was accidentally discontinued during tumour removal. Stenhouse et al
described a case with pseudomixoma peritonei associated with urachal adenocarcinoma in situ.10
According to these authors the patient’s morbidity and prognosis will probably be determined by the peritoneal implants. These were also seen in the patient reported by DeKorté.16
The patient died with numerous mucinous peritoneal implants three years after presentation. Local recurrence was not reported in the earlier series,3, 7, 12
but was seen in our patient because of incomplete resection of the lesion.
Urinary mucous is a common and relatively specific symptom for adenomas of the lower urachus.7
This symptom was reported in seven of 11 symptomatic patients in whom the adenoma involved the lower portion of the urachus.7
The other reported symptoms, including haematuria, pain, and urinary frequency and mass, are common to many bladder diseases.
Take home messages
- We believe that this is only the third patient with urachal adenocarcinoma with features of early stromal invasion and associated with a villous tumour to be described
- We identified a morphological transition from mucinous epithelium and villous adenoma to invasive adenocarcinoma originating from the urachal remnants in our patient
In conclusion, a morphological transition from mucinous epithelium and villous adenoma to invasive adenocarcinoma originating from the urachal remnants was identified in our patient. To the best of our knowledge, only two previous cases of early stromal invasion associated with a villous tumour in the dome of the bladder have been described.3, 12