Primary Renal Carcinoid Tumor Presenting as an Unusual Calcific Mass

ABSTRACT

Calcification in nonrenal carcinoid tumors is common, but it is extremely rare to find calcification in renal carcinoids. Neuroendocrine cells are not found in normal renal parenchyma. We report a case of a 45-year-old male who presented with vague abdominal pain. Investigations showed that he had a calcified mass in the left kidney. We performed a nephrectomy. Histopathological tests showed that it was a carcinoid tumor. The patient was investigated further, but there was no evidence of any extrarenal primary focus of a carcinoid tumor. Whenever a carcinoid of the kidney is diagnosed, a thorough evaluation for another focus of carcinoid tumor is mandated because 54% of reported cases have metastatic lesions at initial presentation. When present, calcification is considered a stigmata of long-term tumor growth and associated with a more indolent course.


Sanjay Kolte, Darshana Tote, Bhushan Wani, Shivashankar Reddy, Girish Moghe

Submitted December 20, 2010 - Accepted for Publication January 31, 2011


KEYWORDS: Renal calcification; Carcinoid tumor

CORRESPONDENCE: Dr. Sanjay Kolte, 35 Balraj Marg, Dhantoli, Nagpur, Maharashtra, 440012, India ().

CITATION: Urotoday Int J. 2011 Jun;4(3):art28. doi: 10.3834/uij.1944-5784.2011.06.02

ABBREVIATIONS AND ACRONYMS: CT, computed tomography; GI, gastrointestinal.

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INTRODUCTION

Carcinoid tumors are commonly found in the gastrointestinal (GI) tract; the most common sites are the appendix and small intestine. The incidence of primary renal carcinoids is very low, and only 62 cases have been reported in the English literature. Carcinoid tumors of the kidney are unusual because neuroendocrine cells are not found in normal renal parenchyma [1]. Patients with horseshoe kidneys have a relatively increased risk of carcinoid tumors [2]. Although calcification in nonrenal carcinoid tumors is common, it is extremely rare to find calcification in renal carcinoids. The present case is one such rare example.

CASE REPORT

A 45-year-old male presented to us with vague abdominal pain in the left flank of 1-year duration. There was no history of hematuria, hypertension, or any other systemic illness. There were no features of a carcinoid syndrome.

An X-ray of the kidney, ureter, and bladder (KUB) revealed a calcific shadow resembling a ball of cotton or wool in the region of the left kidney (Figure 1). An intravenous urogram (IVU) confirmed the presence of calcification in the left kidney (Figure 2). A computed tomography (CT) scan revealed a 6 cm x 5 cm calcific mass situated in the upper half of the left kidney, reaching up to the hilum. There was no evidence of early-onset neovascularization, lymph node enlargement, or perinephric invasion (Figure 3). The remaining urinary tract was normal. The left adrenal gland was not involved. There was no evidence of metastasis either in the liver or anywhere in the abdomen or chest.

A nephrectomy was performed. On gross examination, the mass was well-encapsulated without any breach of the renal capsule. It had woody-hard tissue on the cut section. Histopathology of the tumor on hematoxylin and eosin staining showed that the tumor was composed of nests of cells. The cells had a good amount of cytoplasm, round and minimally pleomorphic nuclei, and low mitotic activity. There was no necrosis. Immunohistochemistry revealed cytoplasmic positivity for synaptophysin and chromogranin (Figure 4; Figure 5), thus confirming the diagnosis of carcinoid tumor.

Postoperatively, an octreotide nuclear scan showed that there was no evidence of any other focus of carcinoid tumor anywhere in the body. There was no evidence of any neuroendocrine substances in the blood. At a follow-up of 2 years, the patient is asymptomatic and tumor-free.

DISCUSSION

Carcinoid tumors are low-grade malignant tumors commonly found in the GI and respiratory tract. They are very uncommon in the urogenital system; the kidney represents the site in 19% of the patients; the testes, prostate, and bladder represent the site in 55%,15%, and 9% of the patients, respectively. In the kidney, 26.8% of the carcinoid tumors are associated with another renal pathology [3]. Carcinoid tumors have been found in polycystic kidneys [4] and in horseshoe kidneys [5]. Primitive stem cells within the kidney or retained neural crest tissue may give rise to these tumors [2]. Only 1 case of metastatic renal carcinoid was found in the literature [6].

The median age of carcinoid tumor presentation is 49 years. There is slight male preponderance with a male:female ratio of 1.5:1. The right side is more often involved than the left in a ratio 61%:39%. The reported incidence of this tumor is increasing, with 22 cases presented between 1996 and 2005. The more common use of imaging in modern practice may be leading to a more frequent diagnosis of clinically silent tumors [3].

Whenever a carcinoid of the kidney is diagnosed, a thorough evaluation for another focus of carcinoid tumor is mandated. This is because 54% of reported cases have metastatic lesions at initial presentation [4]. Isolated renal carcinoids are very rare. Calcification in renal carcinoids is also very rare. When present, calcification is considered a stigmata of long-term tumor growth and associated with a more indolent course [1].

The literature on this topic is still scarce and the clinical course and prognosis of this tumor cannot be predicted. The treatment of choice for localized tumors is complete surgical excision. In our patient, the calcification seen on the X-ray was very unusual and not indicative of any known causes of calcification related to diseases of the kidney. The most common causes of calcification in the kidney in India are: (1) Genitourinary Kochs, where the calcification has a lobar pattern; (2) calculus disease, which is very obvious by its presence in the collecting system; and (3) renal cell carcinomas, where there is no fixed pattern of calcification. The diagnosis of carcinoid in the present case could be made only after surgical removal and histopathology.

This case is presented because primary renal carcinoid is extremely rare. It is often asymptomatic and hence, a diagnostic dilemma. The CT findings are also nonspecific. Although surgical excision is the mainstay of treatment, nephron-sparing surgery is preferred if the diagnosis is established preoperatively [7]. Differentiation between renal carcinoids and the more common renal neoplasms (eg, renal cell carcinoma, transitional cell carcinoma) can be difficult because clinical, radiographic, and histopathologic features overlap [1]. This implies that any unusual calcific mass in the kidney should also raise a suspicion of a primary renal carcinoid tumor so that, in selected cases, a nephron-sparing surgery may be offered.

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