Renal oncopathology in adults, as a field of pathology, is dominated by a single entity -
clear cell renal cell carcinoma (RCC) with other entries, such as urothelial
carcinoma of the renal pelvis,
angiosarcoma, and others being extremely rare. Herein, we report two histopathological cases with differential diagnoses of spindle cell
renal neoplasms. The first patient, a 42-year-old male, presented with new-onset right-sided abdominal
flank pain, and imaging showed a 12 cm renal
tumor. Histopathology showed a spindle cell
neoplasm, with significant mitotic activity and giant cell, with immunohistochemistry being positive for
caldesmon and
vimentin, focally for smooth muscle actin (SMA). No reaction was noted for pan-
cytokeratin (CK AE1/AE3),
epithelial membrane antigen (EMA),
cytokeratin (CK) 7, cluster of differentiation (CD) 117, soluble 100
protein (S100), human
melanoma black (HMB) 45,
Melan A, CD10, and
desmin. Due to peculiar histomorphology and the immunophenotype, the
tumor was interpreted as primary renal
leiomyosarcoma. Due to continuous outpatient consultations, treatment initiation was delayed, and three months later, the patient had already developed an 87 mm local recurrence and liver
metastasis. The second patient, a 53-year-old male, presented to our institution for consultation of an already excised renal
tumor, diagnosed as an incidental finding on a prophylactic abdominal ultrasound. The
tumor presented for consultation histologically grew as intertwining bundles of spindle cells with polymorphic hyperchromic nuclei with prominent nucleoli and had extensive areas with
necrosis. Immunohistochemically, the
tumor diffusely expressed CK AE1/AE3 and
caldesmon and had a patchy reaction for EMA and CD10. The SMA,
desmin, CD117, and CK7 reactions were negative; hence, the
tumor was interpreted as a spindle cell variety (sub-type) of clear RCC.