A RARE PRESENTATION OF SMALL CELL LUNG CARCINOMA METASTASIZING TO PHEOCHROMOCYTOMA

Abstract

Abstract Introduction/Objective Tumor-to-tumor metastasis is a rare phenomenon in which primary tumor cells metastasize hematogenously into another unrelated tumor. We report an interesting case of a tumor-to-tumor metastasis of small cell lung carcinoma to pheochromocytoma of the adrenal gland. Methods/Case Report A 75-year-old female former cigarette smoker with a past medical history of hypertension presented with a two-day history of dyspnea and epigastric pain. Physical examination demonstrated elevated blood pressure only. A computerized axial tomography scan of the chest and abdomen showed an incidental 3.1 cm right adrenal mass and right hilar lymphadenopathy. Detailed biochemical workup showed elevated serum epinephrine, norepinephrine, and 24-hour urine metanephrine. Adrenalectomy showed a 5.8 cm tumor mass with solid lobulated yellow to pink-tan and focally hemorrhagic cut surfaces. Microscopic examination showed a neoplasm composed of two distinct components. The predominant component consisted of nests ("zellballen") of large polygonal cells with variable nuclear pleomorphism, abundant amphophilic to basophilic cytoplasm, and a delicate intervening fibrovascular stroma, without significant mitotic activity. The minor component was characterized by sheets and nests of "small blue cells" with round to ovoid nuclei, stippled nuclear chromatin pattern, scanty cytoplasm, patchy necrosis, and high mitotic activity (>20 mitoses per 10 HPF). Foci of small cell carcinoma deposits were also present in the lymphatic channels of pheochromocytoma. Immunohistochemical stains demonstrated cytoplasmic staining of predominant component tumor cells for synaptophysin, chromogranin, and the absence of staining for TTF-1, CK CAM 5.2, and Ki-67. However, minor component tumor cells demonstrated cytoplasmic staining for synaptophysin, membranous staining for CK CAM 5.2, and nuclear staining for TTF-1 and Ki-67(60%). A final diagnosis of composite pheochromocytoma (predominant) and small cell neuroendocrine carcinoma (minor) was rendered. The possibility of a” collision” tumor comprising primary small cell carcinoma of pulmonary origin metastatic to an adrenal pheochromocytoma in light of the patient's cigarette smoking history and the presence of right hilar lymphadenopathy was favored. The subsequent biopsy of the right subcarinal adenopathy showed small cell carcinoma. Results (if a Case Study enter NA) NA Conclusion To the best of our knowledge, this is the only case of metastasis to a pheochromocytoma from a small cell neuroendocrine lung carcinoma.