Introduction Clear cell sarcoma of kidney (CCSK) is a rare malignancy accounting for <0.5% of all primary renal tumors, commonly diagnosed between 2 and 4 years of age and rarely occurring in early infancy. The challenging differentiation between CCSK and blastemal Wilms tumor is important because of the distinct clinical pattern of CCSK to recur and metastasize to bone and brain. The aim of this study is to discern subtle features that could assist pathologists in diagnosing CCSK in infancy. Method In-depth comparison of clinical, histological, and immunohistochemical findings in a case of CCSK diagnosed at 5 months of age with two cases of CCSK diagnosed at 2 and 3 years of age. Results Both groups were male, and each presented with an abdominal mass. Grossly, a single, firm, well-demarcated tumor, morphologically comprising monotonous small primitive round-to-polygonal/spindle cells, was seen in both groups. The major differences between the study groups were growth patterns and stromal reactions. In infancy, the growth pattern was diffusely uniform sheets of malignant cells with no entrapment of tubules and inconspicuous stromal changes. However, in childhood cases, the growth pattern included well-defined tubular entrapment, as well as focal microcyst formation, myxomatous stroma, palisading bodies, and anaplastic and/or rhabdoid histology. In both study groups, the immunohistochemistry showed strong immunoreactivity with cyclin D1 and nonspecific positivity for vimentin, CD99, and BAF47. Conclusion CCSK has notoriously diverse histological heterogeneity and mimics other pediatric renal tumors, making diagnosis treacherous, and commonly erroneous as Wilms tumor with unfavorable histology. Despite the advent of immunohistochemical and molecular techniques, a thorough morphologic analysis remains key in accurately diagnosing CCSK at any age, especially in early infancy. This small in-depth comparison of CCSK by age groups suggests that tubular entrapment and stromal changes may be less conspicuous in CCSK in early infancy than at older ages.
Testicular germ cell tumors (TGCTs) may spontaneously regress, making it a diagnostic challenge. We present here a case of 39-year-old African American male with constant abdominal pain radiating into the back. Computed tomography identified bulky retroperitoneal lymphadenopathy. There was no history of testicular trauma. Ultrasonography of right testicle revealed multiple microcalcifications, and a laboratory test indicated elevated beta-hCG and LDH. Patient underwent right orchiectomy, which revealed a grossly well-demarcated white oval lesion (3.1 cm). Histologic examination identified a fibrotic lesion in a background of atrophic parenchyma consistent with scar tissue. The specimen was completely submitted for microscopic evaluation, but neoplasia was not identified. A placental alkaline phosphatase (PLAP) immunohistochemical stain failed to reveal residual germ cell neoplasm in situ. Biopsy of retroperitoneal lymph node identified malignant neoplastic cells expressing PLAP, CD117, CD30, and cytokeratin AE1/AE3. The morphology and immunophenotype were consistent with metastatic germ cell tumor. Spontaneous regression of TGCT is defined as partial or complete tumor disappearance without any treatment. The clinical presentation could be nonspecific. Histologically, tumor regression is indicated by formation of fibrous scar, testicular atrophy, microcalcification, lymphoplasmacytic infiltration, and hemosiderin-phagocytosed macrophages, all of which were present in the current case. However, similar histological features could be identified in testicular ischemia or infraction. Therefore, the diagnosis of complete regression of TGCT is challenging and frequently relies on the present of extragonadal germ cell tumor. In the current case, we reported a spontaneous complete regression of TGCT, supported by a spectrum of histological features and metastasis to retroperitoneal lymph node. Spontaneous regression of TGCT is rare, with less than 150 cases reported in the literature. Since there is a lack of definitive histologic criteria to diagnose complete spontaneous regression of TGCT, when scarring is seen in the testis, additional clinical and imaging evaluation should be followed.
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