Perivascular Epithelioid Cell Tumor
It is a neoplasm with smooth muscle and melanocytic differentiation which arises from perivascular epithelioid cells.
Very uncommon tumors. No association with tuberous sclerosis
Most reported cases between 19 and 48 years
No sex predilection
Most cases arise in the kidney (angiomyolipoma) that should be described elsewhere, but with anecdotal cases described in the bladder or prostate (Martignoni et al. 2015).
The majority of the cases have shown a benign course with only a few malignant cases with metastatic disease.
PEComa shows typically a solid well-circumscribed or infiltrative tumor with a size range of 0.5–9 cm in greatest dimension.
The tumor may show two patterns, epithelioid and spindled, with one dominant pattern. Epithelioid pattern is arranged in nests and spindled pattern in fascicles. The epithelioid component is associated with blood vessel. Tumor cells show clear or eosinophilic cytoplasm. The tumor involves the bladder wall, and the covering urothelium is unremarkable (Fig. 1); in the prostate gland, the tumor is surrounded by normal appearing glands. Necrosis may be present, a finding related to malignant behavior in one case (Pan et al. 2003; Weinreb et al. 2007; Sukov et al. 2009).
Tumor cells stain with melanocytic markers HMB45 (Fig. 2) and MART1, muscle-specific actin, tyrosinase, cathepsin K, and TFE3.
TFE3 gene rearrangement has been reported (Williamson et al. 2013).
References and Further Reading
- Williamson, S. R., Bunde, P. J., Montironi, R., & Lopez-Beltran, A. (2013). Malignant perivascular epithelioid cell neoplasm (PEComa) of the urinary bladder with TFE3 gene rearrangement: Clinicopathologic, immunohistochemical, and molecular features. The American Journal of Surgical Pathology, 37, 1619–1626.CrossRefGoogle Scholar