Oncocytic Adrenocortical Carcinoma: A Morphologic, Immunohistochemical and Ultrastructural Study of Four Cases
Mai P. Hoang, M.D., Alberto G. Ayala, M.D., Jorge Albores-Saavedra, M.D.
Department of Pathology (MPH, JA-S), University of Texas Southwestern Medical Center, Dallas, Texas; and M.D. Anderson Cancer Center (AGA), Houston, Texas
We present the clinical, histologic, immunohisto- chemical, and ultrastructural findings of four cases of non-functioning oncocytic adrenocortical carci- nomas. The patients’ ages ranged from 39 to 71 years. There was no sex predilection. Large yellow- tan tumors (8.5 to 17.0 cm), well demarcated from the adjacent kidney, were seen with a thin rim of normal adrenal gland along one edge. One tumor invaded the inferior vena cava and extended up to the level of the right atrium, and another metasta- sized to bone. The other two tumors had similar morphologic features and therefore were consid- ered carcinomas. Histologic sections of all four cases showed a diffuse proliferation of polygonal neoplastic cells with large nuclei containing prom- inent nucleoli and abundant granular and eosino- philic cytoplasm. Occasional mononuclear and binucleated giant cells were noted in one case. There were rare mitotic figures (less than one per 10 high power fields). All tumors were immunoreactive for cytokeratins (AE1/AE3 and CAM5.2). Inhibin was focally expressed by one tumor and its bone metas- tasis. Ultrastructurally, the cytoplasm of the neo- plastic cells was packed with innumerable mito- chondria. Cytologic atypia or mitotic rate cannot reliably predict the biologic behavior of oncocytic adrenocortical neoplasms. Large tumor size (4/4), extracapsular extension (3/4), blood vessel invasion (2/4), necrosis (4/4), and metastasis (1/4) are fea- tures of malignancy for oncocytic adrenocortical carcinomas. The treatment of these tumors is com- plete surgical excision.
Copyright @ 2002 by The United States and Canadian Academy of Pathology, Inc.
VOL. 15, NO. 9, P. 973, 2002 Printed in the U.S.A.
Date of acceptance: May 25, 2002.
KEY WORDS: Adrenal cortical neoplasm, Adreno- cortical carcinoma, Oncocytic neoplasm. Mod Pathol 2002;15(9):973-978
Oncocytic adrenocortical neoplasms are rare, usually non-functioning tumors, found predominantly in adults. The majority of those reported have followed a benign clinical course (1-14). To date, three oncocytic adrenocortical carcinomas have been described; however, these cases emphasized only either the clin- ical presentation, the fine needle aspiration findings, or the ultrastructural features (2, 7, 8).
We present the clinical, histologic, immunohisto- chemical, and ultrastructural features of four cases of oncocytic adrenocortical carcinoma. The cyto- pathologic findings of one case have been previ- ously reported RINS
MATERIALS AND METHODS
The consultation file of two of the authors (JA-S, AGA) and the surgical pathology files of the Univer- sity of Texas Southwestern Medical Center, Dallas, and M.D. Anderson Cancer Center, Houston, Texas, were searched for oncocytic adrenocortical carci- nomas. Four cases with available archival materials were identified. The cytopathologic findings of one case (case 1) have previously been published (7). Four-micrometer thick sections were cut from the formalin-fixed, paraffin-embedded blocks and stained with hematoxylin and eosin. Additional paraffin sections of selected blocks were obtained for immunohistochemical studies, which were per- formed on an automated immunostainer (Ventana, Biotek System, Tucson, AZ) using the standard avidin-biotin peroxidase complex technique and the heat-induced epitope retrieval buffer. The pri- mary antibodies are listed in Table 1. For electron microscopic study, tissue of three cases was fixed in 3% glutaraldehyde, postfixed in 1% osmium tetrox- ide, and thin sections were stained with lead citrate
| Antibody | Case 1 | Case 2 | Bone Metastasis | Case 3 | Case 4 | Clone | Dilution | Source |
|---|---|---|---|---|---|---|---|---|
| High molecular weight cytokeratin | + | + | + | + | - | AE1/AE3 | 1:800 | Signet (Dedham, MA) |
| Low molecular weight cytokeratin | ND | + | ND | + | + | CAM 5.2 | 1:4 | Becton Dickinson (Mountain View, CA) |
| Vimentin | + | ND | + | + | + | polyclonal | 1:200 | DAKO (Carpinteria, CA) |
| Synaptophysin | - | ND | + | ND | - | polyclonal | 1:100 | DAKO |
| Chromogranin | - | ND | ND | ND | - | DAK-A3 | 1:700 | DAKO |
| S-100 protein | - | ND | ND | ND | - | polyclonal | 1:1200 | DAKO |
| Inhibin | - | + | + | - | - | polyclonal | 1:20 | Harlan Bioproducts (Indianapolis, IN) |
| P53 | 10% | ND | ND | ND | - | DO7 | 1:50 | DAKO |
| Ki-67 | 10% | ND | ND | 5% | <5% | MIB-1 | 1:40 | Immunotech (Westbrook, ME) |
ND, not done.
and uranyl acetate. All grids were examined with a JEOL 100SX electron microscope (Japan).
RESULTS
Clinical Findings Case 1
A 39-year-old man presented with ascites, bilat- eral lower extremity edema, and abdominal mass. An abdominal computed tomography (CT) and ar- teriography revealed a large mass in the vicinity of the upper pole of the left kidney that invaded the inferior vena cava and extended up to the level of the right atrium. A thorough workup demonstrated no evidence of metastatic disease. He underwent a left radical nephrectomy and a combined cardio- pulmonary bypass with atriotomy and resection of the tumor thrombus from the right atrium and in- ferior vena cava. The patient is free of disease 2 years and 8 months status postsurgery.
Case 2
A 53-year-old woman presented with a 7-month history of abdominal pain. A magnetic resonance imaging (MRI) scan showed a large retroperitoneal mass in the vicinity of the superior pole of the left kidney. A chest CT showed two 0.5 cm pulmonary nodules interpreted as metastases. A left adrenalec- tomy, nephrectomy, distal pancreatectomy, and splenectomy were performed. The patient devel- oped a right proximal tibial metastasis a year later. She is alive with bone and pulmonary metastases 2 years after diagnosis.
Case 3
A 58-year-old man with known right adrenal mass presented with a 1-year-history of marked size increase. MRI showed a large and heterogeneous mass on T1 and T2 weighted images. The tumor displaced the kidney posteroinferiorly, effaced the right lobe of the liver, and caused moderate flatten- ing of the inferior vena cava. A right adrenalectomy
was performed. The patient is well and with no evidence of disease 2 years status postsurgery.
Case 4
A 71-year-old woman presented with a left abdom- inal mass. The left kidney, left adrenal gland, and spleen were resected. At the superior pole of the left kidney, a round, well-demarcated friable mass was seen with no direct attachment to the kidney. A CT scan of the chest and abdomen performed at 5 months status postsurgery demonstrated no evidence of residual or recurrent neoplasm.
Gross Findings
Large tumors, well-demarcated from adjacent kidney, were seen in all four cases. Focally, there was a thin rim of normally appearing adrenal gland along one edge. The tumors measured 8.5, 13.0, 14.0, and 17.0 cm in greatest dimension, and showed a yellow-tan appearance with central stel- late zone of necrosis (Fig. 1). The tumors invaded through the capsule into adjacent fibroadipose tis- sue in two cases (cases 1 and 2) and focally into the capsule in 1 case (case 3). Extension into the adre- nal vein and renal vein was noted in case 1.
Microscopic Findings
The adrenal glands of all four cases were almost completely replaced by a partially encapsulated neoplasm. Only a thin rim of residual normal adre- nal gland remained. The polygonal neoplastic on- cocytic cells were seen arranged predominantly in a diffuse pattern (Fig. 2). In some areas, nests and trabeculae of neoplastic cells separated by sinu- soids lined by flattened endothelial cells were iden- tified (Fig. 3). Large irregular zones of necrosis were noted. The neoplastic cells were large, round to polygonal, with round nuclei and prominent nucle- oli, and abundant granular and eosinophilic cyto- plasm (Fig. 4). Giant mononuclear and binucleated cells were seen in one case (case 4). Focal bizarre
FIGURE 1. A large multinodular yellow tumor with central necrosis is seen replacing the adrenal gland and compressing the kidney.
FIGURE 3. Trabeculae of tumor cells are separated by dilated sinusoids lined by endothelial cells.
cytologic atypia was noted in the remaining three cases. Clusters of neoplastic cells with foamy cyto- plasm were noted in two tumors (Fig. 5). There were rare mitotic figures (less than one per 10 high power fields). Vascular invasion, outside of the tu- mors, was identified in two cases and extra capsular extension in three tumors.
Histologic sections of the tumor thrombus (case 1) and bone metastasis (case 2) showed a diffuse
FIGURE 4. The neoplastic cells have abundant granular and eosinophilic cytoplasm. A binucleated cell with prominent nucleoli is seen.
proliferation of oncocytic neoplastic cells whose morphology was similar to that of the primary ad- renal tumors.
The immunohistochemical results of four onco- cytic adrenocortical carcinomas and the bone me- tastasis are summarized in Table 1. All tumors were immunoreactive for cytokeratins (AE1/AE3 and CAM5.2) (Fig. 6). Inhibin was focally yet strongly positive in one tumor and its bone metastasis (Fig.
7). The tumors were negative for synaptophysin, chromogranin and S-100 protein.
Ultrastructural Findings
The cytoplasm of the neoplastic cells of three tumors was packed with innumerable mitochon-
dria (Fig. 8). Lipid droplets and well-developed rough endoplasmic reticulum were identified. The abundant smooth endoplasmic reticulum and tu- bular cristae commonly seen in conventional adre- nal cortical adenoma were not prominent features. The nuclei had prominent nucleoli.
I
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DISCUSSION KINS
Twenty-seven cases of adrenocortical oncocytic neoplasms have been reported to date, which com- prised 22 oncocytomas, 2 oncocytic neoplasms of uncertain malignant potential, and 3 oncocytic car- cinomas (1-14). All arose in the adrenal gland with
ibited
| Case No. or Reference | Age (y)/Sex | Presenting Symptoms | Size (cm) | Weight (g) | Necrosis | Vascular Invasion | High Nuclear Grade | Eosinophilic cytoplasm | Diffuse Growth | Capsular Invasion | Mitotic Activity | Follow-Up |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Case 1 | 39/M | Ascites, abdominal mass | 14.0 | NA | + | Invading the L adrenal vein, L renal vein, IVC, and extending up to the R atrium | - | + | + | + | <1/10 HPF | NED 3 mo s/p surgery |
| Case 2 | 53/F | 7-mo history of abdominal pain | 17.0 | 1200 | + | + | - | + | + | + | <1/10 HPF | Bone metastasis 1 y s/p surgery |
| Case 3 | 58/M | 1-y history of rapidly enlarging adrenal mass | 13.0 | 740 | - | - | + | + | + | <1/10 HPF | NED 2 y s/p surgery | |
| Case 4 | 71/M | L abdominal mass | 8.5 | 100 | - | + | + | + | - | <1/10 HPF | NED 5 mo s/p surgery | |
| Kurek (8) El-Naggar et al. (2) | 74/F 56/M | Incidental finding by abdominal CT Acute abdominal pain | Unau NA 10.0 | NA NA | WILLIAMS | NA Invading the IVC and the posterior segment of the liver | NA NA | + + | + + | NA - | NA NA | Recurrence, ovarian metastasis 7 y s/p surgery NA |
M, male; F, female; +, present; - , absent; NA, not available; CT, computed tomography; L, left; R, right; IVC, inferior vena cava; HPF, high-power field; NED, no evidence of disease; s/p, status post.
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the exception of one oncocytoma that originated in heterotopic right supra-adrenal retroperitoneal tis- sue (11). All have been reported to be nonfunctional except one oncocytic adenoma that produced vir- ilizing symptoms (3).
The main differential diagnosis of our cases is ad- renal cortical oncocytoma. The majority of adrenal cortical oncocytomas are well-circumscribed tumors with size ranging from 3 to 15 cm. Although they show cytologic atypia, necrosis, capsular extension and vas- cular invasion are not identified. The differential di- agnosis also includes conventional adrenal cortical carcinoma, pheochromocytoma, eosinophilic variant of chromophobe renal cell carcinoma, and metastatic hepatocellular carcinoma. Many adrenocortical tu- mors have foci of oncocytic neoplastic cells (15); how- ever, our tumors were composed exclusively of onco- cytes. Neoplastic cells with foamy cytoplasm were only noted focally in two cases (less than 5%). Inhibin has recently been shown to stain the majority of ad- renocortical tumors (16); however, it was expressed in only one of our four cases of oncocytic adrenocortical carcinomas. Pheochromocytomas are functional tu- mors that produce episodic hypertension. They have a zellballen pattern and exhibit chromogranin immu- noreactivity and the sustentacular cells express S-100 protein. Moreover, electron microscopy would reveal abundant dense-core membrane-bound granules rather than mitochondria. The oncocytic variant of renal cell carcinoma may involve the adrenal gland. However, renal cell carcinomas are usually immuno- reactive for epithelial membrane antigen and have cytoplasmic vesicles ultrastructurally and are inhibin negative (17). Our tumors focally have a trabecular pattern with cords of neoplastic cells separated by sinusoids, lined by flattened endothelial cells. Hepar-1 immunostain would easily exclude the pos- sibility of metastatic hepatocellular carcinoma.
Various systems have been proposed to distinguish benign from malignant adrenocortical tumors (18). According to Weiss (19, 20), adrenocortical carcinoma would have four or more of the following findings: high nuclear grade, eosinophilic cytoplasm (more than 75%), diffuse architecture (more than 33%), and presence of necrosis, mitotic figures (more than 5/50HPFs), atypical mitotic figures, capsular invasion, venous invasion, and sinusoidal invasion. Of these, a mitotic rate greater than 5 per 50 HPF, atypical mi- totic figures, and venous invasion were found only in malignant tumors. Other studies of conventional ad- renal cortical carcinoma found that mitotic rate and nuclear pleomorphism were the features most sup- portive of malignancy (15, 21). However, cytologic atypia or mitotic rate cannot reliably predict the bio- logic behavior of oncocytic adrenocortical neoplasms. In reviewing the clinicopathologic features of our four cases and the two previously documented cases of oncocytic adrenocortical carcinomas (Table 2), we
found that all our tumors showed a diffuse prolifera- tion of oncocytic cells with prominent nucleoli but with less than 1 mitotic figure per 10 HPFs. Large tumor size, vascular invasion, capsular extension, me- tastasis and surgical unresectability are features of malignancy for oncocytic adrenocortical carcinomas.
Markers such as P53 and Ki-67 have been proposed to be potential predictive markers of biologic behav- ior of adrenocortical neoplasms (22). However, find- ings in isolated case reports and small series have not shown Ki-67, a proliferation marker, to be useful in oncocytic adrenocortical carcinomas (7, 9). One of our tumors expressed p53, while p53 expression was absent in the benign and borderline oncocytic adre- nocortical tumors in a series by Lin et al. (9). More- over, loss of heterozygosity at 17p, the chromosomal arm that housed the p53 gene locus, was documented by microsatellite analysis of a recurrent oncocytic ad- renocortical carcinoma with ovarian metastasis (8). These findings suggest that p53 tumor suppressor gene may play a role in malignant transformation of some oncocytic adrenocortical neoplasms. Unfortu- nately, the role of either Ki-67 or p53 as biomarkers likely remains uncertain due to the availability of so few of these tumors.
The ultrastructural findings of our cases are similar to those previously reported adrenal oncocytomas and oncocytic adrenocortical carcinomas. The cy- toplasm is filled with numerous mitochondria, re- markable for their abnormalities in size, shape, and cristae structure (23, 24). Minimal knowledge is available of the mechanisms that lead to oncocyto- sis in general and in adrenocortical cells in partic- ular. Experimental studies in rats have demon- strated that N-nitrosomorpholine induced renal oncocytosis and followed by the formation of renal oncocytoma (25). These findings suggest that mito- chondrial proliferation is a compensatory mecha- nism. Another hypothesis is that oncocytomas are tumors of mitochondria since mitochondria have their own DNA that codes their own characteristic proteins (26). Differentiation towards cells of high- energy output, a response to defect in the energy production machinery of the cell, is another possi- ble explanation for the oncocytic appearance of these tumors (27).
We present four cases of non-functioning onco- cytic adrenocortical carcinomas whose malignant biologic behavior is evidenced by direct tumor ex- tension, venous invasion, extracapsular involve- ment and bone metastasis. The treatment of these tumors is complete surgical excision.
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