Fibroma-like PEComa: A Tuberous Sclerosis Complex-related Lesion

Case report: Liver PEComa after kidney transplantation in recipient with tuberous sclerosis complex

Introduction

Perivascular epithelioid cell tumors (PEComa) are rare tumors of mesenchymal origin that exhibit perivascular epithelioid cell phenotype. One of its most common localizations is uterus, whereas only a few studies reported PEComa localization as liver. There is a correlation between the presence of PEComa and tuberous sclerosis complex (TSC). TSC is a rare disease which leads to the development of mostly non-cancerous tumors in various organs. We would like to present a case of a kidney transplant recipient with a PEComa detected post-transplant in the liver.

Case report

A 27-year-old patient, 3 years after kidney transplantation (KTx) due to chronic renal failure in the course of autosomal dominant polycystic kidney disease and concomitant TSC, was admitted to the Clinic and Department of General and Transplant Surgery for abnormal findings in computed tomography (CT). A CT scan was conducted for oncological follow-up after a kidney transplant (KTx) because before the transplantation, a small cystic lesion measuring 7 mm in diameter was removed from the donor kidney and diagnosed as papillary renal cell carcinoma (PRCC). Two tumors in the liver were detected - one 27mm in diameter in segment VII/VIII and the other 8mm in diameter in segment II/III. Because of typical radiological signs hepatocellular carcinoma was suspected, but the serum level of alpha fetoprotein was within normal limits and liver function was preserved. The intraoperative biopsy and the radiofrequency ablation (RFA) of the larger tumor were performed three months later. In the histopathological examination benign PEComa (HMB45 +, Melan A +) was detected.

Conclusion

The oncological surveillance made it possible to detect liver lesion in early stage and in 3,5-year follow-up no sign of recurrence of PEComa was found. This case is the second to show RFA as treatment method of liver PEComa and first in kidney transplant recipient.

Soft Tissue Perivascular Epithelioid Cell Tumors

Perivascular epithelioid cell tumors (PEComas) are a heterogenous group of mesenchymal neoplasms with a mixed myomelanocytic immunophenotype. PEComa-family tumors include angiomyolipoma, lymphangioleiomyomatosis, and a large category of rare neoplasms throughout the body that are now classified under the umbrella term "PEComa." This review focuses on recent advances in the clinicopathological and molecular features of PEComas, with an emphasis on PEComas that originate in soft tissue.

Hepatic perivascular epithelioid cell tumor (PEComa): contrast-enhanced ultrasound (CEUS) characteristics-a case report and literature review

Perivascular epithelioid cell tumors (PEComa) are rare mesenchymal neoplasms that arise from soft tissue of various organs such as the stomach, intestines, and lungs. We report a rare case of a primary PEComa of the liver and its characteristics on contrast-enhanced ultrasound (CEUS) in a 51-year-old female patient with an incidental finding of a hypoechoic liver lesion with peripheral hypervascularization on Doppler ultrasound. CEUS showed homogenous hypervascularity in the arterial phase that was consistent in the portal phase. In the late phase, a central washout phenomenon was evident. Histopathologic findings on sonographic biopsy of the lesion revealed a mesenchymal tumor with positivity for melanocytic markers Human Melanin Black-45 (HMB45) and Melan-A consistent with a PEComa. Despite the absence of high-risk features for malignancy, surgical resection was recommended due to the uncertain malignant potential of PEComas. The patient refused the operation and preferred sonographic follow-up; the lesion was stable over a period of 2 years. CEUS can provide valuable information regarding PEComa. After histological confirmation, the choice between resection and a watchful waiting must be made on individual basis.

Fibroma-like PEComa: a newly recognized soft tissue neoplasm in tuberous sclerosis patients-imaging features and review of literature

Perivascular epithelioid cell tumors (PEComas) are rare mesenchymal neoplasms composed of spindled to epithelioid cells that co-express both melanocytic and myogenic markers. Recently, in 2018, a distinctive variant of PEComa has been described that arises in association with tuberous sclerosis complex (TSC) and resembles a fibroma by conventional morphology (called fibroma-like PEComa). Herein, we describe a case of a fibroma-like PEComa in a 4-year-old male child with a known diagnosis of tuberous sclerosis who presented with a firm mass along the anteromedial aspect of the right knee. The mass was excised, and microscopic examination showed bland spindled to stellate cells embedded in a dense collagenous stroma, morphologically resembling a fibroma. Immunohistochemistry analysis showed positivity for desmin (a myogenic marker) and HMB45 (a melanocytic marker), a hallmark for PEComas. To our knowledge, only six cases of fibroma-like PEComa have been described in the literature so far and this is the first report of such a tumor in the medial retinaculum of the knee joint with illustrations of conventional and diffusion imaging features. This case highlights the unique association of fibroma-like PEComa lesions with TSC. This should be considered a differential diagnosis for T2 hypointense masses in tuberous sclerosis patients. In addition, a diagnosis of fibroma-like PEComa should prompt further evaluation for associated TSC.

Primary cutaneous malignant perivascular epithelioid cell tumor: Case of a rare tumor with review of the literature

Perivascular epithelioid cell tumors (PEComas) are mesenchymal neoplasms with characteristic epithelioid or spindled cytomorphology that typically grow around blood vessels. These tumors are phenotypically and immunohistochemically distinct, expressing markers of both melanocytic and smooth muscle differentiation. Herein, we describe a case of histopathologically malignant cutaneous PEComa without metastatic spread, with review of the pertinent literature. Telescoping punch biopsy demonstrated an epithelioid neoplasm with marked atypia, hypercellularity, and increased mitotic activity. Immunohistochemical stains for HMB-45, NK1-C3, PGP9.5, MiTF, CD10, and CD68 were positive within tumor cells. In addition, there was diffuse expression of caldesmon and focal cytoplasmic staining for smooth muscle actin on the excision specimen. The patient underwent treatment with surgical excision with adjuvant radiation and surveillance computed tomography (CT). The patient remains free of recurrence or metastatic disease after 10 months of follow-up. To our knowledge, this is only the third reported case of a malignant cutaneous PEComa reported in the literature to date.

Fibroma-like perivascular epithelioid cell tumor: a rare case in a long bone

Fibroma-like perivascular epithelioid cell (PEComa) tumor is an extremely rare family of mesenchymal tumors composed of cells co-expressing melanocytic and myogenic markers. To date, 13 cases of primary bone PEComa have been reported in the literature and five reported fibroma-like PEComas were found in the soft tissues of patients with tuberous sclerosis (TSC). However, no fibroma-like PEComa has been reported in bone, either sporadic or TSC-associated. Here we report the case of a 22-year-old man with known TSC, who presented for evaluation of an asymptomatic mass in his left fibula diaphysis that had been present for 5 years. He had no activity-related pain, numbness, weakness, or limitations in range of motion. Both 3-T MRI and CT demonstrated a tumor originating from the midshaft middiaphyseal fibula. Axial T1-weighted and fat-saturated T2-weighted fast spin echo images showed a well-defined lesion in the fibula with extension into the surrounding soft tissues. Whole body bone scan was negative for metastasis using technetium-99m. Renal ultrasound was unremarkable with no evidence of angiomyolipoma. Histopathology demonstrated isolated spindle cells in a dense collagenous matrix. By immunohistochemical staining, tumor cells were positive for HMB-45 and MiTF and partially positive for alpha-smooth muscle actin supporting a diagnosis of fibroma-like PEComa of the midshaft fibula. Although fibroma-like PEComa of bone is very rare, a bone tumor in the setting of TSC should raise suspicion for the diagnosis, in particular if histology demonstrates rare epithelioid cells in a densely fibrotic stroma.

Retroperitoneal Sarcomas: An Update on the Diagnostic Pathology Approach

Retroperitoneal sarcomas are a heterogenous group of rare tumors arising in the retroperitoneum. Retroperitoneal sarcomas comprise approximately 10% of all soft tissue sarcomas. Though any soft tissue sarcoma histologic types may arise in the retroperitoneal space, liposarcoma (especially well-differentiated and dedifferentiated types) and leiomyosarcoma do so most commonly. Retroperitoneal sarcomas are diagnostically challenging, owing to their diversity and morphological overlap with other tumors arising in the retroperitoneum. An accurate diagnosis is necessary for correct management and prognostication. Herein, we provide an update on the diagnostic approach to retroperitoneal sarcomas and review their key histologic findings and differential diagnoses.

Epithelioid Cutaneous Mesenchymal Neoplasms: A Practical Diagnostic Approach

Epithelioid cells are rounded or polygonal cells with abundant eosinophilic or clear cytoplasm and ovoid to round nuclei, superficially resembling epithelial cells. Cutaneous mesenchymal neoplasms composed predominantly or exclusively of epithelioid cells are relatively uncommon and can cause considerable diagnostic difficulties due to overlapping histologic features among heterogeneous groups of tumors. Familiarity with practical diagnostic approaches and recognition of key histopathologic features are important for correct diagnosis and management. This review summarizes the histologic features of epithelioid cutaneous mesenchymal neoplasms and discusses their differential diagnoses from malignant melanomas and carcinomas.

Cutaneous "fibroma-like" perivascular epithelioid cell tumor: A case report and review of literature

Perivascular epithelioid cell tumors (PEComas) are a group of lesions sharing the common features of co-expression of melanocytic and myogenic markers, with focal association of the cells with vascular walls. The PEComa group exhibits a wide range of morphologies. A "fibroma-like" variant of PEComa has been recently described. The case reported herein is that of an infant with tuberous sclerosis complex (TSC) presenting with a lip mass. Excisional biopsy showed a moderately cellular tumor composed of spindled to stellate cells embedded within a collagenized stroma. The cells showed focal perivascular accumulation and positivity for both melanocytic (HMB-45) and myogenic (desmin) markers. This is the fifth reported case of "fibroma-like" PEComa in literature and the youngest patient to date. All of the "fibroma-like" PEComas were found in patients with tuberous sclerosis-hence, the diagnosis of this entity should prompt a workup for TSC; conversely, a fibroma-like lesion in a patient with TSC or with TSC-related conditions should be evaluated using melanocytic and myogenic markers. Melanocytic and myogenic markers are also useful in differentiating "fibroma-like" PEComa from other differential diagnoses such as fibroma and benign fibrous histiocytoma.

Intra-articular fibroma-like perivascular epithelioid tumor (PEComa) mimicking tenosynovial giant cell tumor, diffuse type

Perivascular epithelioid cell tumors (PEComas) are rare mesenchymal neoplasms composed of perivascular epithelioid cells that are immunoreactive for both melanocytic and myogenic markers. Recently, a fibroma-like PEComa associated with tuberous sclerosis complex (TSC) has been identified. We describe the first intra-articular case of a fibroma-like PEComa in a 44-year-old man who presented with a hypointense intra-articular knee mass, which was mistaken for tenosynovial giant cell tumor, diffuse type. This case report demonstrates that fibroma-like PEComa should be included in the extended differential diagnosis of intra-articular soft tissue masses. In addition, given their strong association with TSC mutations, a diagnosis of fibroma-like PEComa should trigger an evaluation for TSC.