This manuscript describes a 67-year-old man who presented with hematuria. Ultrasonogrophic and computer tomography revealed a 5 cm mass in right posterolateral wall of the bladder that invaded perivesical tissue and he subsequently underwent transurethral resection. Microscopic examination showed a tumor with a sheet-like and trabecular growth pattern comprising necrotic areas which infiltrated the muscularis propria. Tumoral cells had coarse chromatin, prominent nucleoli, moderate amount of cytoplasm and immunohistochemically stained strongly positive with synaptophysin, chromogranin and CD56.
There are only few case reports of large cell neuroendocrine tumor of the urinary bladder so the biological behavior and the treatment protocol of these tumors are still obscure. Appropriate management protocols and prognostic estimation could be achived by the increased number of cases being reported. Therefore in a case of a poorly differentiated tumor in bladder, although rare, it is important to consider large cell neuroendocrine carcinoma in differential diagnosis.
Figure 2: Large pleomorphic tumoral cells with active mitosis and pink or pale cytoplasm (H&E x400).
Tumor cells were widespread positive with synaptophysin (Figure 3A), chromogranin, CD56 (Figure 3B) and CK 7 (Figure 4A) and focal positive with CK 20 and p63 (Figure 4B). High molecular weight cytokeratin, TTF-1, PSA and PSAP were negative. An accompanying conventional urothelial carcinoma (UC) area was not observed. The patient was diagnosed with LCNEC, pT2 and died of heart faiure two weeks aft er the TUR surgery.
Figure 3: Tumor cells with (A) synaptophysin positivity (x200), (B) CD 56 positivity (x200).
Figure 4: Tumor cells with (A) cytokeratin 7 positivity (x200), (B) P63 positivity (x400).
LCNEC of the bladder was fi rst described by Aboza et al. in 1986 in a 55-year-old patient and was reported to be associated with adenocarcinoma[10]. Only four of the 14 LCNEC cases reported so far has been in the pure form[4,5,11] and other cases have been accompanied by adenocarcinoma, urothelial carcinoma, squamous cell carcinoma, carcinosarcoma, or lymphoepithelioma-like carcinoma[2,3,10,12,13]. Clinicopathologic findings of the reported cases are summarized in Table I. LCNED was observed in a pure form in the TUR material in our case, but we could not rule out the presence of an accompanying carcinoma since there is a possibility of residue tumor in the bladder.
Table I: Published cases of bladder large cell neuroendocrine carcinoma
The basic features of LCNEC in organs other than the lung such as the bladder, uterus, thymus, stomach, larynx, parotid gland, prostate and kidneys, are histologically similar to their counterpart in the lung[2]. The large size, polygonal shape, low nuclear/cytoplasmic ratio, coarse chromatin structure and frequent nucleoli are the most important features of the cells. More than 10 mitosis in 10 high power fi elds and necrosis are oft en present[2,4]. Synaptophysin, chromogranin and CD56 positivity are present immunohistochemically. LCNEC observed in the lung have been classified as large cell carcinoma variant by the WHO as they show morphological similarity with nonsmall cell lung tumors. However, they are clinically similar to SCC with a very poor prognosis, and similar response to cisplatin-based therapy[2]. As in the lung, bladder SCCs have a poor prognosis and 5-year survival is approximately 8%[3]. Bladder LCNECs also have a rapid course and poor prognosis like SCCs[3,5]. Bladder LCNECs are very rare tumors so there is no specifi c treatment protocol but studies with pulmonary LCNECs show they respond well to standard chemotherapy regimens administered to SCCs[14,15].
The etiology of bladder NE carcinomas has not been elucidated as yet. The most widely accepted hypothesis is that neuroendocrine cells develop from stem cells or multipotent undifferentiated cells in the urothelium. Another theory is that they develop from metaplastic urothelium or high grade urothelial carcinoma[3]. One of the finding which supports this theory is that besides bladder SCCs more than %50 of the bladder LCNECs are found to be associated with more differentiated cell forms such as urothelial carcinoma, and adenocarcinoma. The immunohistochemical heterogenity that both LCNEC and SCC show by staining with epithelial and neuroendocrine determinants to a certain degree also supports the multipotent stem cell theory[4]. Although a conventional urothelial carcinoma area was not observed in our case, the positive staining of LCNEC areas with CK 7 and CK 20 (epithelial markers positive in urothelial carcinoma) in addition to neuroendocrine markers is consistent with the multipotent cell theory. P63 is an urothelial carcinoma determinant and was focal positive in our case. Although this seems to support the theory that LCNEC develops from high-grade urothelial carcinoma, there is no information available in the literature regarding p63 positivity in bladder LCNECs. Buza N. et al showed all 14 of their SCC cases except one to be negative for p63 in a study they conducted on bladder SCCs. However, that study defined p63 positivity as at least 10% of the tumor cells showing staining[17]. More studies are needed to determine the meaning and role of p63 positivity in the differential diagnosis of bladder neuroendocrine carcinomas.
It is important to differentiate bladder LCNEC from metastatic LCNEC originating from other organs, poorly differentiated prostate adenocarcinoma or lymphoma showing local extension, and primary bladder tumors such as high grade UC and squamous cell carcinoma. In the presence of a tumor morphologically similar to LCNEC that needs to be differentiated from high-grade, poorly differentiated UC, the presence of immunohistochemical positivity for neuroendocrine determinants supports LCNEC. The most signifi cant histological features differentiating LCNEC from SCC with similar neuroendocrine characteristics are large cell size, prominent nucleoli, coarse chromatin, low nuclear/cytoplasmic ratio and trabecular organoid arrangement[2].
In conclusion, it is important to keep LCNEC in mind in the presence of a poorly differentiated tumor in the bladder as it has been reported that adjuvant chemotherapy, as well as surgical treatment can ensure long-term control in localized bladder LCNECs similar to pulmonary LCNECs[2]. In addition, the increasing number of reported cases will contribute to the development of appropriate treatment protocols.
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