The urinary bladder can be the site of tumors exhibiting various degrees of endocrine differentiation. It has become the most common site of extrapulmonary small cell undifferentiated carcinoma [6
]. The spectrum of endocrine tumors of the urinary bladder has widened considerably in the past concerning both its morphological feature and its clinical behaviour. The better differentiated members of this group, carcinoid tumors, have an organoid arrangement, with trabecular and glandular patterns of growth, and its origin in the urinary bladder is extremely rare. To the best of our knowledge only 6 cases of primary carcinoid tumor of the bladder have been reported [1
The present case shows clinically and microscopically the same features showed by two cases of carcinoid of urinary bladder reported recently by Martignoni and Eble [1
]. Their review of the literature disclosed 4 previously reported pure carcinoid tumors of the urinary bladder. These 6 cases and the present case show a striking clinical and pathological overlapping, as shown in tab .
Clinicopathologic profiles of patients with carcinoid tumor of the urinary bladder.
All 6 cases presented with hematuria, most of the patients aged of seven decade. All tumors were small, polypoid nodules at cystoscopy and most of them were localized in the neck of the bladder or trigone. All previously reported 6 tumors and the present case show a glandular architecture. Previous study, and our results have demonstrated the neuroendocrine differentiation. Strikingly the present case showed, immunohistochemically, a strongly reactivity with calcitonin. To the best of our knowledge this is the first case of a well-differentiated neuroendocrine carcinoma of the urinary bladder reported positive with this neuropeptide.
Some tumors could simulate carcinoid of the bladder, in particular the nested variant of transitional cell carcinoma; differences in the cytologic features and immunohistochemistry should establish the diagnosis. The distinction between carcinoid tumor and inverted papilloma with glandular differentiation can be very difficult, however strong staining for neuroendocrine markers support the diagnosis of carcinoid tumor. Like the classic carcinoid tumors of the appendix, small bowel, or lung, all of the carcinoid tumors of the bladder are histologically and clinically not aggressive.
In conclusion, we here add another case of carcinoid tumor of the urinary bladder to the existing literature, this tumor shows specific clinical, macroscopical and histological features and must be considered in the differential diagnosis of bladder neoplasms.