COW-2020-30

1. c
2. d

1. Vascular transformation of lymph node sinuses
2. ERG

In this case, the patient had a 10.8-cm clear cell renal cell carcinoma involving the renal sinus and vein (ISUP grade 3; pT3a). On microscopic examination, the kidney mass was composed of clear cells arranged predominantly in nests, alveoli, and tubules with a prominent interconnecting network of small chicken-wire like blood vessels. Tumor cells predominantly contained abundant clear cytoplasm with foci containing bright eosinophilic cytoplasm. Nuclei were large and moderately pleomorphic with vesicular chromatin and prominent nucleoli, visible at 100x magnification. Necrosis, sarcomatoid differentiation, nor rhabdoid features were observed. Additionally, multiple enlarged lymph nodes were found involved by a nodular and focally infiltrative spindle cell proliferation extending inward into nodal parenchyma from the sinuses. Lesional nuclei within the lymph node were cytologically different from the kidney primary: they were round to oval with moderate eosinophilic cytoplasm, vesicular to granular chromatin, small nucleoli, scattered nuclear grooves, convoluted nuclear folds, and frequent mitoses (5 /10 hpf). No significant cytologic atypia was present and small capillaries were entrapped within the proliferation. Immunohistochemical stains were performed: SMA, CD34, and ERG (pictured) were positive; HHV-8, Warthin-starry histochemical stain, PAX-2, PAX-8, and pan-cytokeratin (AE1/AE3) were negative. A diagnosis of Vascular Transformation of the Lymph Node Sinuses (VTS) was rendered.

The pathogenesis of VTS is incompletely understood, but postulated to arise as result of occlusion of efferent lymphatics, so it is frequently seen in the context of retroperitoneal malignancy. Immunohistochemistry is reflective of pericytic origin: ERG (pictured), Ulex europaeus agglutinin I, SMA, vimentin, factor VIII antigen, and CD34 are frequently positive and keratin is frequently negative. On occasion, VTS can mimic metastatic sarcomatoid tumor, resulting in potentially grave clinical implications, including unnecessary adjuvant therapy. The prognostic implications of node positive disease in renal cell carcinoma is ominous. By contrast, VTS is a benign process, and excision is curative.

Sarcomatoid renal cell carcinoma nuclei are larger and more atypical than the ones present in VTS, expressing keratin the vast majority of the time. Angiomyolipoma (AML) contains smooth muscle, blood vessels, and adipose—the latter is absent in VTS as a neoplastic component. AML also expresses HMB45 and other melanocytic markers, which are negative in VTS. Metastatic clear cell carcinoma would have features similar to the primary kidney tumor—i.e., large cells with clear to eosinophilic cytoplasm and nuclei with prominent macronucleoli—as well as keratin positivity. Kaposi sarcoma is a low-grade, spindle-cell, vascular neoplasm caused by human herpes virus-8 (HHV-8), often seen in the context of human immunodeficiency virus (HIV) infection and acquired immunodeficiency syndrome (AIDS). Morphologically, KS generally has less fibrosis, more nuclear atypia, and more mitoses than VTS, and the characteristic cytoplasmic eosinophilic hyaline globules seen in KS are absent in VTS.

1. Cook PD, Czerniak B, Chan JKC, et al. Nodular spindle-cell vascular transformation of lymph nodes: A benign process occurring predominantly in retroperitoneal lymph nodes draining carcinomas that can simulate Kaposi’s sarcoma or metastatic tumor. Am J Surg Pathol. 1995;19(9):1010-1020.

2. Chan JKC, Frizzera G, Fletcher CDM, Rosai J. Primary vascular tumors of lymph nodes other than Kaposi’s sarcoma: Analysis of 39 cases and delineation of two new entities. Am J Surg Pathol. 1992;16(4):335-350.

3. Cheville JC, Lohse CM, Zincke H, et al. Sarcomatoid renal cell carcinoma: an examination of underlying histologic subtype and an analysis of associations with patient outcome. Am J Surg Pathol. 2004;28(6):435-441. 4. Mignano SE, Russell DH. Nodular vascular transformation of the lymph node sinuses mimicking sarcomatoid change in renal cell carcinoma: a potential diagnostic pitfall. Int J Surg Pathol. 2020. Pending publication.

Salvatore E. Mignano (Mignanos1@gmail.com)
Daniel H. Russell (russdanny22@gmail.com)
Tripler Army Medical Center

Kidney

Kidney, metastatic renal cell carcinoma, vascular proliferations, sarcomatoid differentiation