Radiology

Dr. Kim: The initial magnetic resonance imaging (MRI) scan of the abdomen was requested by the primary care physician.

Radiology: The main finding on magnetic resonance imaging is an enhancing soft-tissue mass measuring 5 x 3.8 cm in the anterior portion of the right kidney (Figure 3). Additionally, there is a 2 x 1.5-cm complex cystic structure inferior to the mass. The right main renal artery, renal vein, and inferior vena cava appear patent.

Dr. Kim: Let us review the scans of the mediastinal mass.

Radiology: A 24-hour status postradionuclide administration of 5.3 μCi indium-111 pentetreotide (OctreoScan IV), whole-body anterior/posterior imaging was obtained. Single-photon emission computed tomography (SPECT) imaging of the body from the chest, abdomen, and pelvis was also obtained and reviewed in the transaxial, coronal, and sagittal projections. The chest showed nodular foci of mildly to moderately increased radiotracer uptake in both pulmonary hilar regions (Figure 4). This is suspicious for metastatic adenopathy, as physiologic uptake is not normally visualized in lymph nodes. The lung parenchyma is negative for abnormally increased uptake.

These findings are suspicious for bilateral hilar metastatic adenopathy, although the uptake in this region is mildly increased, relative to the physiologic uptake seen in the abdominal organs. There is no increased uptake in any other lymph node region. An area of minor uptake is seen in the right-upper quadrant of the abdomen, most likely relating to the gallbladder.

Follow-up with a noncontrast CT of the chest revealed lobulated hilar masses, bilaterally, with the right greater than left (Figure 5). Small mediastinal lymph nodes are also noted, although no axillary lymphadenopathy is present.

Medical Management

Dr. Kim: What are the medical management considerations for carcinoid tumor of the kidney?

Dr. Thomas W. Flaig: Primary carcinoid tumors of the kidney are rare,[2] with one recent review describing a total of 56 cases in the English medical literature.[3] The average size of these tumors was 8 cm, with those greater than 4 cm having a worse prognosis than those less than 4 cm. Although not a feature in this case, primary carcinoid of the kidney is associated with horseshoe kidneys and teratoma of the kidneys. The mainstay of treatment and the only curative modality for carcinoid of the kidney is complete surgical resection.

For patients with metastatic carcinoid, several medical interventions are available. Most carcinoid tumors express the somatostatin receptor, and this can be assessed with somatostatin receptor scintigraphy (ie, octreotide scan).[4] The somatostatin analog octreotide is effective in slowing tumor growth and palliating symptoms such as diarrhea and flushing in some cases.[5] However, neuroendocrine syndromes are uncommon in cases of renal carcinoid, with a reported frequency of 12% in the literature.[3] Significant tumor regression with octreotide treatment is uncommon. Patients treated with octreotide may develop side effects such as abdominal discomfort, nausea, and loose stools.

The utility of traditional chemotherapy in treating carcinoid tumors is limited. The efficacy of single-agent therapy has been disappointing, but some combination regimens demonstrate improved activity with response rates of 20% to 30%.[6] One new approach under investigation is the use of radiolabeled somatostatin analogs, which allow for a physical targeting of the somatostatin receptor–expressing tumors with targeted radiation.[7]

In this patient's management, I would recommend upper and lower gastrointestinal endoscopy to rule out another site of carcinoid, since primary kidney carcinoid is rare. Additionally, a serum chromogranin and urinary 5-hydroxyindoleacetic acid (5-HIAA) should be obtained as baseline measurements.

Synchronous Carcinoid and Sarcoid Tumors

Dr. Kim: What is known about the relationship of synchronous carcinoid and sarcoid tumors?

Dr. La Rosa: Carcinoid tumors are low-grade malignant tumors that arise from neuroendocrine cells. These tumors are histologically divided into typical carcinoids, which are considered benign tumors with an excellent prognosis after surgical excision, and atypical carcinoids, considered low-grade malignant tumors with potential for local invasion and distant metastases.

The synchronous appearance of carcinoid and sarcoid tumors is an even more rare event. Certain malignant lesions have the tendency to occur in patients with sarcoidosis, but it is unclear which of these tumors appears first.[8] Only seven patients between the ages of 31 and 66 years with both sarcoidosis and carcinoid tumors have been reported in 44 years at the Mayo Clinic Rochester.[9]

The simultaneous appearance of malignant tumors and sarcoidosis may be explained in one of two ways. First, it appears that some immunologic abnormalities related to sarcoidosis may promote the development of some neoplastic processes. Second, some malignant diseases may promote the onset of sarcoidosis, either by causing a local sarcoid reaction that evolves in a more disseminated fashion or by directly initiating systemic mechanisms to induce sarcoidosis. Because the chronology of events have differed in the cases reported in the literature, various mechanisms of action may have played a role in the manifestations of these two disease entities.

Since carcinoid tumors are neuroendocrine tumors characterized by their ability to express somatostatin receptors, they can be imaged with radiolabeled somatostatin analogs. Based on different patterns of radiotracer activity seen on 111In-pentetreotide and 18F-fluorodeoxyglucose positron-emission tomography (FDG-PET), it is now possible to differentiate regional metastatic carcinoid lymphadenopathy from a sarcoid lymphadenopathy.[10]

The case presented in this Second Opinion discussion, emphasizes the importance of avoiding the diagnosis of disseminated malignant disease in patients with cancer and associated hilar and mediastinal lymphadenopathy before we have the results of a biopsy and pathologic confirmation of metastatic disease. If available, functional imaging studies can complement this differential diagnosis.[10]

Concluding Remarks

Dr. Kim: Renal carcinoid tumors are exceedingly rare tumors that have been primarily documented as case reports in the literature.[2] Primary renal carcinoid tumors seem to be more indolent than renal cell carcinomas, although metastases to regional lymph nodes, liver, and bone have been described. The presence of metastases seems to indicate a more malignant course. However, even with metastases, a patient might live 3 or 4 years.

Renal carcinoid is the second most prevalent genitourinary carcinoid in each sex, following testicular carcinoid tumors in men and ovarian tumors in women. Significant adverse prognostic factors include age greater than 40 years, tumor size greater than 4 cm, purely solid tumors on the cut surface, mitotic rate higher than 1/10 high-power fields, metastasis at initial diagnosis, and tumors extending throughout the renal capsule.

Renal carcinoid tumors should be managed by radical or partial nephrectomy, and in the era of minimally invasive surgery, the laparoscopic approach offers faster recovery, better cosmetics, and less hospitalization—as depicted in this case—without compromising the principles of oncologic surgery. Good outcomes have been reported for organ-confined disease after radical excision. Conventional methods of imaging are inadequate for detecting smaller carcinoid tumors. Thus, somatostatin receptor scintigraphy should complement CT and MRI when searching for occult or metastatic disease. Close follow-up after surgery is necessary.[11]