Background：
To investigate the immunohistochemical and clinicopathological behaviors of primary urinary tract small cell carcinomas (SCCs).
Methods：
A retrospective study of 10 cases of urinary tract SCC (7 men and 3 women, average age, 54; range, 35-78 years) at Chang Gung Memorial Hospital is reported. Among these cases, 3 tumors arose from the kidney, 2 from the renal pelvis, 2 from the ureter, and 3 from the bladder. Clinical and follow-up data were obtained. Histological and immunohistochemical studies with antibodies to neuroendocrine (NE) markers were conducted.
Results：
The most prominent common feature of the 10 SCCs was their cell histopathology: small to medium-sized round to spindle-shaped cells with scanty cytoplasm, hyperchromatic nuclei, and inconspicuous nucleoli. Immunostaining revealed positive neuron-specific enolase (NSE) reactivity in 10 of 10 tumors, but there was focal and weak staining for chromogranin-A (CgA) in 4 of 10 tumors. The 7 patients with vimentin-positive SCCs all developed metastatic lesions, and 5 of them expired within 1 year.
Conclusion：
SCCs of the urinary tract system share similar histopathological features and NE markers with their pulmonary counterpart. NSE was expressed more consistently than CgA in these tumors. However, the preferential expression of NSE and intensity of immunostaining of these 2 NE markers did not predict the clinical outcome of these patients. The presence of both SCC and transitional cell carcinoma or SCC alone did not foretell the clinical outcome either. Patients with the presence of vimentin in the tumor tissues appeared to have poorer prognoses with early metastasis and mortality. (Chang Gung Med J 2003;26:26-33)
Keywords：
small cell carcinoma, kidney, urinary bladder, transitional cell carcinoma, neuroendocrine markers.

METHODS

Ten cases of primary SCC of the urinary system were collected from the tumor registry at Chang Gung Memorial Hospital between 1988 and 1999. The medical records were reviewed, and clinical and follow-up data were obtained. The pathological diagnosis for SCC fulfilled the criteria set forth by the World Health Organization in all cases. The renal tumors were staged based on Robson's criteria; renal pelvis, ureter, and bladder tumors were staged based on the Jewett-Marshall scheme. Immunohistochem-ical staining was performed on sections of 10 formalin-fixed, paraffin-embedded tissues using the avidin-biotin peroxidase complex (ABC) method. The Vectastain ABC kit was provided by Vector Laboratories (Burlingame, CA). Tissue sections were stained with a panel of monoclonal and polyclonal antibodies. The sources of these antibodies and the designations of hybridoma clones from which monoclonal antibodies (MAbs) were generated are listed in Table 1. The stainibility of these antibodies is known not to be affected by either formalin fixation or paraffin embedding.

RESULTS

Clinicopathological characteristics. The clinical data on patients are summarized in Table 2. Patient age at presentation, gender, location and stage of the disease, clinical symptoms, type of management, site of metastasis, follow-up duration, and cause of death were noted.
There were 7 male and 3 female patients; the average age of all patients at presentation was 54 (range, 35-78) years. Of the 10 patients, 3 had tumors arising from the kidney, 2 from the renal pelvis, 2 from the ureter, and 3 from the urinary bladder. There was no prostatic SCC in this report. The chief complaint of those patients with renal pelvis, ureter, or bladder tumors was gross hematuria. Patients with renal tumors presented with flank pain, body weight loss, and palpable abdominal masses.
Of the renal tumors in 3 patients, 2 were stage III, and the other patient had tumor invasion of the abdominal wall (stage IV) (Fig. 1). A radical nephrectomy was performed in these patients, followed by adjuvant chemotherapy with cyclophosphamide, epidoxorubicin, and vincristin. Unfortunately, these patients developed early metastases, and 2 expired within 9 months. Of the 3 patients with renal pelvis tumors, 2 whose tumors were at stage D expired 6 months after the operation; the other patient with a stage B tumor (case 5) developed multiple metastases (lung, bone, and lymph nodes) and survived for 31 months after a nephroureterectomy. In the 2 patients with ureter tumors, 1 had a ureteral stone, and a superficial tumor was found simultaneously. He received a nephroureterectomy but developed neck lymph node metastasis and expired 17 months later. Another patient, who had previously received segmental resection of his ureter due to in situ carcinoma, had a recurrent ureteral tumor (stage C), and was disease-free for 55 months after a nephroureterectomy. The 3 patients in the bladder tumor group had an average age of 74 (range, 69-78) years, which was much older than the other groups. One patient was diagnosed with a stage D1 tumor, and received palliative transurethral resection of the bladder tumor due to hematuria. He passed away 3 months later. A partial cystectomy was performed on the patient with a stage C tumor, and this patient expired 7 months after the operation because of respiratory failure. The third patient with a stage B tumor is still being followed-up after a radical cystectomy.
Most of the patients developed early metastases (Table 2). The preferential sites for metastases were the lungs and lymph nodes, and occurred in 5 patients. Other frequent metastatic sites were bone and liver.

Histological characteristics. The renal tumors were mostly large in size, measuring up to 20×10×8 cm with central necrosis (Fig. 1), and the renal pelvis tumors, also appearing as large tumor masses, were often found to have invaded the renal parenchyma. Most of the tumors in the urinary bladder were flat, infiltrating, and necrotic in appearance. The light-microscopic features of the small cell carcinomatous component were similar in all tumors. Most of the tumor cells were small, ovoid to spindle-shaped with hyperchromatic nuclei and scanty cytoplasm (Fig. 2A). In the 6 tumors with a histology of mixed transitional cell carcinoma (TCC) and SCC, tumor nests of the 2 components were found to exist separately in the same tissue. The histology of 1 such tumor (case 9) is depicted in Fig. 2B.

Immunohistochemical features. Immunostaining was performed in the 10 cases for the expression of neuron-specific enolase (NSE), chromogranin-A (CgA), cytokeratin AE1/AE3, vimentin, epithelial membrane antigen (EMA), and leukocyte common antigen (LCA), and in 7 cases for S100a and S100b. The results are summarized in Table 3.
Of the 10 SCCs examined, 6 stained strongly (++), 3 moderately (+), and 1 weakly (+/-) for NSE. As for CgA, 1 stained intensively, 1 moderately, 2 weakly and focally, and the remaining 6 gave negative results. Eight stained moderately, 1 weakly, and 1 negatively for AE1/AE3 (Fig. 3). One tumor intensively stained, 5 moderately stained, 1 weakly stained, and 3 negatively stained for vimentin. Two tumors stained moderately, 3 weakly and focally, and the remaining 5 negatively for EMA. None of the 10 tumor specimens tested gave positive staining results for LCA in tumor areas, signifying that the tumor cells studied were not of a lymphoid nature.

DISCUSSION

Extrapulmonary SCCs are rare and rather malignant. Since the first report of such a carcinoma of the mediastinal gland by Duguid in 1930,(6) cases of extrapulmonary SCCs of various organs have been sporadically reported from organs such as the cervix, esophagus, endometrium, skin, prostate, urinary bladder, and kidney as well as other unusual sites. In general, these tumors respond poorly to treatment with chemotherapeutic agents, and the prognosis with these tumors is poor and varies considerably from case to case. For instance, in the genitourinary tract most of the reported SCCs are mainly of the prostate and urinary bladder. SCC of the kidney is more malignant and rapidly fatal as compared with non-SCCs in spite of adjuvant chemotherapy.(4,6,7)
We encountered no prostate SCC in our 3 affiliated hospitals during the period from 1988 and 1999. This is not too surprising in view of the fact that there was a low incidence of prostate cancer in Taiwan, with a rate of 14.25/100,000.(8)
Clinically, all patients presented with symptoms of involvement of a specific organ or a few organs. There were no specific clinical indicators that would have directed the attention of clinicians to SCC. SCC is generally diagnosed by its histologic characteristics, which are not dissimilar from those of its pulmonary counterpart.(9) Histologically, tumor cells are small, ovoid to spindle-shaped with hyperchromatic nuclei and scanty cytoplasm. Negative LCA reactivity excludes the possibility of lymphoid cells. Ultrastructurally, SCC cells have been described as having oval, moderately irregular nuclei with dense chromatin peripherally.
The histogenesis of SCC has been controversial. Pearse demonstrated the ability of small cells to synthesize and store amines and to decarboxylate certain amino acids to form amines,(9) and termed these cells APUD (amine precursor uptake and decarboxylation) cells. In urothelial cancers, the presence of both small cell and transitional cell components may imply the multipotential origin of this tumor.(3) It has been proposed that renal SCCs originate from metanephrogenic blastemas or the renal pelvis epithelium.(10,11) Some investigators believe that these tumors are of multipotential origin, or from "basal" cells with pleuripotentialities.(12) In this report, most of the tumors of the urinary bladder, ureter, and renal pelvis (6/10) were of mixed components of high-grade TCC and SCC. The coexistence of these 2 different cell types in the urothelium and the expression of NSE markers in the transitional cell component may indicate that SCC is the most malignant variant of epithelial neoplasms, or that it is likely to have originated from multipotential epithelium with divergent differentiation. In primary renal small cell tumors, the renal parenchyma tissue is often found to be replaced by small, round neuroendocrine tumor cells in varying degrees. This may imply the possibility of the dedifferentiation of renal tubule cells in primary renal SCC. While the presence of a mixed tumor histotype or of SCC alone failed to reveal any prognostic significance, the number of cases in our series is too small to draw a definitive conclusion in this regard.
As found in the pulmonary counterpart, SCCs of the urinary system in our series mostly expressed NSE and less frequently CgA. SCC cells are known to express some NE markers, such as NSE, CgA, bombesin, synaptophysin, and calcitonin.(13) NSE is found in extracts of brain tissue and in APUD cells of the neuroendocrine system and their tumors.(14) NSE, however, has also been identified in some non-neuroendocrine tumors, such as carcinomas, fibroadenomas, and lymphomas.(15) CgA is a constituent of the secretory granules of most peptide-producing endocrine cells, and its presence is usually associated with a number of cytoplasmic-dense core granules.(16) However, secretory granules in SCC cells seen by electron microscopy do not always accompany the detection of CgA. Negative to focally weak expression of CgA in SCCs (cases 5, 6, and 7) seemed to indicate a better prognosis. The preferential expression of NSE and staining intensity of either of the 2 NE markers by tumor cells did not correlate with the disease status or prognosis of urinary SCCs. However, the number of cases is too small in our series to draw any definitive conclusions. NSE could only be used for the identification of the neuroendocrine component of this tumor.
Seven of the 10 SCC tumors in this study stained positively for vimentin. The 7 patients with vimentin-positive SCCs all developed metastatic lesions, and 5 of them expired within 1 year. Two patients (cases 5 and 7) without vimentin expression in their tumor tissues survived for much longer periods of 31 and over 55 months, respectively. The scattered or focal expression of vimentin in most of our cases (7/10) of urinary SCC is intriguing. While the biologic role of vimentin in SCCs of the urinary tract remains unclear, indirect evidence from clinical observations indicates that neoexpression of this intermediate microfilament in primary breast carcinomas is associated with an increased rate of metastatic potential.(17) The presence of vimentin may therefore predict a more-aggressive SCC and a graver outcome.
Clinically, SCC progressed rapidly in our patients; 5 patients developed lung metastases, 5 lymph node metastases, 2 bone metastases, and 1 liver metastasis. Three of the 5 patients had lymph node metastases at presentation; 1 developed lung metastasis 6 months after surgery (case 3). Of the 5 patients with lung metastases, 1 developed both bone and lymph node metastases, and 1 developed bone metastasis. Most of the patients died within 1 year after metastasis was detected, despite aggressive adjuvant chemotherapy. Thus, multimodality therapies should be considered, including radical resection followed by early irradiation and chemotherapy.(3) Systemic combination chemotherapy is highly recommended. Ideally, chemosensitivity and extreme drug resistance assays should be performed to select more-effective drugs and at the same time avoid the toxicity of potentially ineffective drugs, respectively.(18) This approach to cancer patient management has gained much attention in recent years.(19)
In conclusion, SCC of the urinary tract is generally rare, but is a highly malignant disease. It has a similar histology to that of its pulmonary counterpart, and possesses NE cell markers such as expression of NSE and/or CgA. The presence of vimentin in urinary small cell tumor tissues appears to indicate a poorer prognosis, and early metastasis tended to develop. The origin of SCC of the urinary tract still remains inconclusive. The presence of both high-grade TCC and SCC components in a tumor tissue may indicate the pleuripotentiality of this tumor or dedifferentiation of the malignant urothelium. However, the prognostic significance is yet to be determined. Diagnosis of SCC depends largely on its histopathologic characteristics and NE markers. Early diagnosis and radical surgery followed by early adjuvant chemotherapy and radiotherapy are still the golden rule for the management of urinary SCCs. Unlike pulmonary SCCs, cultures of small cell carcinomas of the urinary tract are rarely available; thus the establishment of a cell line would be useful for further studies aimed at uncovering the biology of this rare cancer and at elucidating the role of vimentin expression in the aggressiveness and progression of SCCs.(20)

Acknowledgements

The authors gratefully acknowledge Drs. Y-S Ho and K-F Ng (Department of Pathology, Chang Gung Memorial Hospital, Taoyuan, Taiwan) for reviewing the histopathology. This work was supported in part by the Chang Gung Medical Research Fund (CMRP-713).

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From the 1Division of Urology, Department of Surgery, Chang Gung Memorial Hospital, Taipei; 2Graduate Institute of Clinical Medicine, Chang Gung University, Taoyuan.
Received: Jul. 31, 2002; Accepted: Oct. 1, 2002
Address for reprints: Dr. Cheng-Keng Chuang, Division of Urology, Department of Surgery, Chang Gung Memorial Hospital. 5, Fu-Shing Street, Kweishan, Taoyuan 333, Taiwan, R.O.C. Tel.: 886-3-3281200 ext. 2103; Fax: 886-3-3285818; E-mail: chuang89@cgmh.org.tw