Collision tumor of kidney: A case of renal cell carcinoma with metastases of prostatic adenocarcinoma
A 72-year-old male had complaints of loss of appetite and constipation since 5 months. Per rectal examination revealed an enlarged hard-fixed prostate gland adherent to the rectal wall without luminal compromise. The pre-operative Prostate-Specific Antigen (PSA) was 19.9 ng/mL. As the patient had locally advanced prostate cancer, he was planned to be managed with neoadjuvant hormonal treatment followed by locoregional pelvic radiotherapy and further hormonal treatment. Hence, he initially underwent a bilateral orchidectomy for hormonal ablation, but defaulted for further treatment. A direct transurethral stenting was performed additionally to relieve him of lower urinary tract symptoms.\nThe patient presented 8 months later after defaulting, with backache and extensive bone pain. The serum PSA levels and serum alkaline phosphatase were -950 ng/mL and 1262 U/L, respectively. The bone scan confirmed extensive skeletal metastasis. On ultrasonography, a left-sided renal mass was noted measuring 5.9 cm × 5.5 cm × 5.4 cm. In addition, multiple enlarged left inguinal and paraaortic nodes were seen. As the mass was solid cystic in nature, radiologic impression of RCC was favored as metastatic prostate cancer was unlikely to be cystic. A left radical nephrectomy was performed at another institute and the specimen was sent as referral for histopathological examination and diagnosis at our tertiary cancer institute.\nThe radical nephrectomy specimen on gross revealed a well-circumscribed necrotic tumor measuring 5.7 cm × 5.2 cm × 4.8 cm involving the upper two-thirds of the kidney ([], thick arrow). The adjacent cortical area appeared firm and pale white ([], thin arrow). The renal sinus or the Gerota's fascia was not infiltrated by the tumor. A smooth cyst measuring 4 cm × 3.5 cm × 3 cm was seen at the lower pole ([], arrow head). A firm nodule with a grey-white cut-surface measuring 1.2 cm in diameter was seen adherent to the kidney at the hilum ([], asterix). The adrenal gland was unremarkable.\nThe tumor at the upper pole was confirmed to be conventional RCC, Fuhrman nuclear grade 2. Random sections from the adjacent pale kidney showed extensive cortical metastasis of prostatic adenocarcinoma, without actual admixture of the two tumor components. The prostatic adenocarcinoma comprised of recognizable acinar/glandular elements in a confluent sheeting pattern. The cyst at the lower pole was a simple cortical cyst. The perinephric fat and the Gerota's fascia were not infiltrated by the tumor. Extensive lymphatic emboli of prostatic adenocarcinoma were noted. The adjacent kidney also revealed features of chronic pyelonephritis. On immunohistochemistry, the tumor at the upper pole (RCC) was positive for CK, vimentin and CD10. The metastatic prostatic adenocarcinoma was negative for CK7, CK20, CD10, HMWCK, vimentin and PSA [Figure –]. A diagnosis of collision tumor, i.e., conventional RCC along with extensive parenchymal involvement by prostatic adenocarcinoma was rendered. The patient expired 1 month after the surgery due to the extensive nature of the metastatic prostate cancer and debilitating general condition, accentuated by the post-operative status of the patient.