Microscopic view of perivascular epithelioid cells.

Rare Prostate Tumor: A Benign PEComa Case

Kai Mendoza in Health & Wellness December 2025 • 4 min read.

"A closer look at perivascular epithelioid cell tumors (PEComas) and a unique case of a benign prostatic PEComa, offering insights for diagnosis and treatment."

Perivascular epithelioid cell tumors, or PEComas, are a rare type of mesenchymal tumor. These tumors can develop in various locations throughout the body. What makes PEComas unique is the presence of perivascular epithelioid cells. These cells share characteristics of both muscle and melanocytes (pigment-producing cells), expressing markers associated with both.

PEComas are often benign, some can become aggressive, exhibiting characteristics like rapid growth or the ability to spread to other parts of the body (metastasis). When possible, surgical removal is the preferred treatment. In situations where surgery isn't an option, radiation therapy, chemotherapy, and immunotherapy have been explored, either alone or in combination.

When it comes to the prostate, PEComas are extremely rare. This article explores the first reported case of a benign prostatic PEComa, successfully treated with transurethral resection. This case offers valuable insights into the diagnosis and management of this unusual tumor.

Decoding PEComas: What Makes Them Unique?

Microscopic view of perivascular epithelioid cells.

The World Health Organization defines PEComas based on their distinct histological and immunohistochemical features. These tumors are primarily composed of epithelioid cells that stain positive for HMB-45, a melanocytic marker. These cells typically have clear or granular cytoplasm and a centrally located nucleus.

PEComas require careful differentiation from other tumors with similar appearances. This includes clear cell sarcoma, paraganglioma, melanoma, metastatic carcinoma (especially from kidney or adrenal gland), and smooth muscle tumors.

Clear Cell Sarcoma: Vascular stroma and perivascular arrangement is not common in clear cell sarcoma, and nearly all are positive for $100 protein.
The prostatic tumor showed low mitotic activity, coagulative necrosis and malignant behavior.
PEComa, shows strong and diffuse staining for only HMB-45 in the spindle and epithelioid cell components.

The absence of epithelial markers and the positive expression of HMB-45 helps to exclude carcinoma and smooth muscle tumors from the diagnosis. In the case described, the tumor cells were positive only for HMB45 with a diffuse staining pattern, which supported the PEComa diagnosis.

The Future of PEComa Treatment: A Call for More Research

This report highlights the first documented instance of a benign prostatic PEComa, accompanied by extended follow-up. While most PEComa lesions tend to be benign, certain tumors exhibit malignant characteristics and aggressive clinical progression, including the potential for distant metastasis.

Currently, there is no established effective medical treatment for individuals with advanced PEComa. To accurately forecast the biological behavior of PEComas and determine the most effective treatment strategies, further research involving additional cases and longer follow-up periods is essential.

As our understanding of PEComas deepens, new targeted therapies may emerge as definitive treatments for localized aggressive and metastatic cases, offering hope for improved outcomes. This case contributes valuable data to the growing body of knowledge surrounding PEComas.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.5489/cuaj.1752, Alternate LINK

Title: Primary Perivascular Epithelioid Cell Tumour (Pecoma) Of The Prostate

Subject: Urology

Journal: Canadian Urological Association Journal

Publisher: Canadian Urological Association Journal

Authors: Alper Eken, Yesim Saglican

Published: 2014-06-19

Everything You Need To Know

What are PEComas?

PEComas, or perivascular epithelioid cell tumors, are rare mesenchymal tumors characterized by perivascular epithelioid cells. These cells possess features of both muscle and melanocytes, expressing related markers. While PEComas can appear in various parts of the body, the article focuses on a specific instance within the prostate, highlighting its rarity and significance.

What are the key characteristics that define a PEComa?

PEComas are primarily composed of epithelioid cells that stain positive for HMB-45, a melanocytic marker. The World Health Organization defines them by their histological and immunohistochemical features. The cells typically display clear or granular cytoplasm and a centrally located nucleus. This distinct makeup helps in differentiating PEComas from other tumors like clear cell sarcoma, paraganglioma, melanoma, metastatic carcinoma, and smooth muscle tumors.

How are PEComas diagnosed?

The diagnosis involves careful differentiation from other tumors with similar appearances, as mentioned previously, like clear cell sarcoma. In this specific instance, the prostatic tumor showed low mitotic activity, coagulative necrosis and malignant behavior, showing distinct markers. The presence of HMB-45, along with the absence of epithelial markers, supports the diagnosis of PEComa.

How are PEComas treated?

The preferred treatment for PEComas is surgical removal when feasible. However, the approach can change when surgery is not an option. In those cases, treatments like radiation therapy, chemotherapy, and immunotherapy are considered, either alone or in combination. The specific case discussed involved a benign prostatic PEComa, which was successfully treated with transurethral resection.

Why is the reported case significant?

The report offers valuable insights into the diagnosis and management of this unusual tumor. While most PEComas are benign, some can exhibit malignant characteristics and aggressive clinical progression, including distant metastasis. The case of a benign prostatic PEComa is significant because it is the first reported case of its kind with an extended follow-up, contributing to the current body of knowledge about this rare tumor.