Uterine Leiomyosarcoma Associated With Perivascular Epithelioid Cell Tumor: A Phenomenon of Differentiation/Dedifferentiation and Evidence Suggesting Cell-of-Origin.

Perivascular epithelioid cell tumor (PEComa) is a mesenchymal tumor thought to originate from perivascular epithelioid cells (PECs). The normal counterpart to PEC, however, has not been identified in any human organ, and the debate as to whether PEComa is related to smooth muscle tumors has persisted for many years. The current series characterizes 4 cases of uterine leiomyosarcoma (LMS) coexisting with PEComas. All cases exhibited an abrupt transition from the LMS to PEComa components. The LMS component displayed typical spindled morphology and fascicular growth pattern and was diffusely positive for desmin and smooth muscle myosin heavy chain, completely negative for HMB-45 and Melan A, and either negative or had focal/weak expression of cathepsin K and GPNMB. In contrast, the PEComa tumor cells in case 1 contained glycogen or lipid-distended cytoplasm with a foamy appearance (low grade), and in cases 2, 3, and 4, they displayed a similar morphology characterized by epithelioid cells with eosinophilic and granular cytoplasm and high-grade nuclear atypia. Different from the LMS component, the epithelioid PEComa cells in all cases were focally positive for HMB-45, and diffusely immunoreactive for cathepsin K and GPNMB. Melan A was focally positive in cases 1 and 3. Loss of fumarate hydratase expression (case 1) and RB1 expression (cases 2, 3, 4) was identified in both LMS and PEComa components, indicating that they are clonally related. In addition, both components showed an identical TP53 p.R196* somatic mutation and complete loss of p53 and ATRX expression in case 2 and complete loss of p53 expression in case 3. We hypothesize that LMSs containing smooth muscle progenitor cells may give rise to divergent, lineage-specific PEComatous lesions through differentiation or dedifferentiation. While we do not dispute the recognition of PEComas as a distinct entity, we advocate the hypothesis that modified smooth muscle cells represent the origin of a subset of PEComas, and our case series provides evidence to suggest this theory.

Perivascular epithelioid cell tumor of the uterine cervix identified on the liquid-based cytology: a case report.

BACKGROUND: Perivascular epithelioid cell tumor (PEComa) occurring in the female genital tract are rare, and typically found in the uterine corpus. PEComa occurring in the cervix is extremely rare, and very few cases have been reported till now. Cytological diagnosis of cervical PEComa is even rarer. So far, only two cases of PEComa diagnosed by conventional cervical smears have been reported. CASE PRESENTATION: A 55-year-old postmenopausal woman presented with abnormal vagina discharge for 3 months. A liquid-based cytology test was performed. Microscopically, some loosely cohesive epithelioid cells were uniform with abundant clear cytoplasm, showing predominantly round or oval nuclei with finely stippled chromatin. Distinct round nucleoli were visible in some cells, notably with numerous melanin pigments in the cytoplasm. The cytopathological features were well correlated with cell block and histopathological findings. Upon immunohistochemistry (IHC), the tumor cells were positive for HMB45 and TFE3, focally positive for MelanA, while negative for muscle marker. Fluorescence in situ hybridization (FISH) confirmed TFE3 gene rearrangement. The final pathological diagnosis was PEComa identified by the liquid-based cytology, cell block, cervical biopsy, IHC and FISH result. The patient underwent a total hysterectomy with bilateral salpingo-oophorectomy and was followed up for 2 years with no evidence of disease. CONCLUSION: The cytologic characteristics of the tumor can provide sufficient clues for PEComa diagnosis, which includes loosely cohesive, epithelioid morphology with abundant clear or eosinophilic cytoplasm, low-grade nuclear atypia, cytoplasmic melanin pigments. This will help cytopathologists to recognize this rare tumor that occurred in the cervix, and the combination of predictive morphology evaluation, immunophenotype, and molecular testing can achieve the definitive diagnosis of PEComa.

Primitive Cutaneous (P)erivascular (E)pithelioid (C)ell Tumour (PEComa): A New Case Report of a Rare Cutaneous Tumor.

Perivascular epithelioid cell tumours (PEComas) are a growing family of tumours composed of histologically and immunohistochemically distinctive perivascular epithelioid cells. Cutaneous primitive PEComas (cPEComas) are very rare, with 65 cases described in the English literature, and occur as a painless lesion predominantly in female patients, with a wide age range. We present a new case of cPEComa found on the left thigh of a 53-year-old patient with histopathological, immunohistochemical, and molecular information. The lesion was positive for HMB-45 and focal for smooth muscle actin and desmin but negative for melan-A, S-100 protein, CD31, and CD34. Next generation sequencing (NGS) analysis demonstrated the presence of genomic aberration for baculoviral IAP repeats containing BIRC3 splice site 1622-27_1631del37. Although there are little molecular data regarding this entity, our case adds to this knowledge, considering the importance of detecting genomic aberrations in the context of specific therapies such as mTOR inhibitors.

Ocular PEComas are frequently melanotic and TFE3-translocated: report of two cases including the first description of PRCC-TFE3 fusion in PEComa.

Ocular perivascular epithelioid cell tumor (PEComa) is exceedingly rare. We reported two examples involving the choroid and subconjunctival tissue, respectively, in patients aged 17 and 20 years. Both tumors comprised packets and sheets of large polygonal cells with moderately pleomorphic nuclei and prominent nucleoli, traversed by delicate fibrovascular septa. Melanin pigmentation was present in one case. The tumors showed HMB45 and TFE3 immunoreactivity. TFE3 gene translocation was confirmed by FISH break-apart probes. RNA seq revealed PRCC-TFE3 and NONO-TFE3 fusions, with the former representing the first description of PRCC-TFE3 in PEComa. Critical reappraisal of the reported cases showed that ocular PEComa frequently affected young patents with melanin pigmentation, frequent TFE3 protein expression, and/or TFE3 gene translocation. No recurrence or metastasis was reported after complete excision despite the presence of cytologic atypia.

PNL2: A Useful Adjunct Biomarker to HMB45 in the Diagnosis of Uterine Perivascular Epithelioid Cell Tumor (PEComa).

Perivascular epithelioid cell tumors (PEComa) are rare neoplasms characterized by co-expression of melanocytic and muscle markers. HMB45 and Melan-A are used to confirm a PEComa diagnosis; however, both are often focally expressed and sensitivity for Melan-A is low. PNL2 is a reliable biomarker for epithelioid melanoma and renal angiomyolipoma/PEComa. The objective of this study was to determine PNL2 utility in diagnosing uterine PEComas as well as distinguishing PEComas from uterine smooth muscle tumors (SMTs). Twenty-one uterine PEComas and 45 SMTs were analyzed for PNL2; a subset was also stained for HMB45, Melan-A, Cathepsin-K, Desmin, and h-Caldesmon. Cases were scored as negative (0), focal (<10% of tumor cells), or patchy to diffusely positive (>10% of tumor cells). PEComas were positive for PNL2, HMB45, and Melan-A in 86%, 100%, and 57% of cases, respectively. In PEComas, PNL2 was patchy to diffusely positive more frequently (10/18, 56%) than Melan-A (4/12, 33%). In contrast, 2 of 45 (4%) SMTs were focally PNL2 positive; HMB45 was focally positive in 4 SMTs (11%) and all were negative for Melan-A. Desmin and h-Caldesmon were positive in 90% and 57% of PEComas, and 91% and 82% of SMTs. Cathepsin-K was positive in 100% of PEComas and 93% of SMTs. PNL2 is a useful biomarker for the diagnosis of uterine PEComa, with comparable sensitivity and specificity to HMB45. In contrast, PNL2 stains more PEComas when compared with Melan-A. Cathepsin-K, Desmin, and h-Caldesmon are of little utility for distinguishing PEComas and SMTs; however, lack of Cathepsin-K argues against PEComa. These results suggest that PNL2 should be used in conjunction with HMB45 in the diagnosis of PEComa of the uterine corpus.

PGR Gene Fusions Identify a Molecular Subset of Uterine Epithelioid Leiomyosarcoma With Rhabdoid Features.

Genetic aberrations among uterine epithelioid leiomyosarcomas are unknown. Following identification of an index case with NR4A3-PGR fusion demonstrating monomorphic morphologic features, we interrogated additional uterine tumors demonstrating similar histology and sought to describe the morphologic and immunohistochemical characteristics of PGR-rearranged sarcomas. Targeted next-generation RNA sequencing was performed on RNA extracted from formalin-fixed paraffin-embedded tissue of the index case. Fluorescence in situ hybridization using custom probes flanking PGR and NR4A3 genes was applied to 17 epithelioid leiomyosarcomas, 6 endometrial stromal tumors, and 3 perivascular epithelioid cell tumors. NR4A3-PGR fusion (n=4) and PGR rearrangement (n=2) were detected in 6 (35%) epithelioid leiomyosarcomas. Median patient age was 45 years, and all presented with FIGO stage I or II tumors, 2 being alive with disease at 75 and 180 months. All tumors were centered in the cervical stroma or myometrium and consisted of cells with abundant eosinophilic cytoplasm (epithelioid), including many displaying dense intracytoplasmic inclusions (rhabdoid). Myxoid matrix and hydropic change imparted a microcystic growth pattern in 4 tumors. Five also showed a minor spindle cell component which was low-grade in 3, consisting of bland spindle cells with low mitotic activity. High-grade spindle cell morphology was seen in 2 tumors, exhibiting a storiform pattern of atypical spindle cells associated with brisk mitotic activity. Desmin, estrogen receptor, and progesterone receptor were positive in all 6 tumors, while CD10 and HMB45 were negative. PGR rearrangements define a genetic subset of epithelioid leiomyosarcomas with often biphasic morphology consisting of epithelioid and rhabdoid as well as spindle cell components.

Tibial perivascular epithelioid cell tumour (PEComa). A case report and literature review. / Neoplasia de células epiteloides perivasculares (PEComa) tibial. Reporte de un caso y revisión de la literatura.

INTRODUCTION: Perivascular epithelioid cell (PEC) is a cell type constantly present in a group of tumours including angiomyolipoma (AML), clear-cell «sugar¼ tumour (CCST) of the lung and extrapulmonary sites, lymphangioleiomyomatosis (LAM), and clear-cell tumours of other anatomical sites. It has morphologic distinctive features: epithelioid appearance with a clear to granular cytoplasm, a round to oval, centrally located nucleus and an inconspicuous nucleolus. Immunohistochemically, PEC expresses myogenic and melanocytic markers. Eleven cases of primary bone PEComa presentation have been described since 2002. OBJECTIVE: To report a case of primary bone perivascular epithelioid cell tumour. CASE REPORT: 24 year-old male presented with pain. X-ray revealed an osteolytic lesion at right proximal tibia with soft tissue extension. Evaluation of slides identified a bony perivascular epithelioid cell tumour without immunohistochemical study confirmation. RESULTS: Patient was treated by surgical excision and adjuvant chemotherapy (epirubicin/cysplatin). After two years of follow-up the patient remains disease free. CONCLUSIONS: This is the first-case report in Latin America. Immunohistochemical stains were negative and we believe it may be due to non-described ethnic variations.

Uterine PEComas: A Morphologic, Immunohistochemical, and Molecular Analysis of 32 Tumors.

Uterine perivascular epithelioid cell tumors (PEComas) are rare neoplasms that may show overlapping morphology and immunohistochemistry with uterine smooth muscle tumors. In this study, we evaluated the morphologic, immunohistochemical, and molecular features of 32 PEComas, including 11 with aggressive behavior. Two distinct morphologies were observed: classic (n=30) and those with a lymphangioleiomyomatosis appearance (n=2). In the former, patients ranged from 32 to 77 (mean: 51) years and 13% had tuberous sclerosis. Tumors ranged from 0.2 to 17 (mean: 5.5) cm with 77% arising in the corpus. Epithelioid cells were present in 100% and a spindled component was seen in 37%. Nuclear atypia was low (53%), intermediate (17%), or high (30%). Mitoses ranged from 0 to 36 (mean: 6) and 0 to 133 (mean: 19) per 10 and 50 high-power fields, with atypical mitoses present in 30%. Thin and delicate vessels were noted in 100%, clear/eosinophilic and granular cytoplasm in 93%, stromal hyalinization in 73%, necrosis in 30%, and lymphovascular invasion in 10%. All tumors were positive for HMB-45, cathepsin K, and at least one muscle marker, with most expressing melan-A (77%) and/or MiTF (79%). A PSF-TFE3 fusion was identified in one while another showed a RAD51B-OPHN1 fusion. Follow-up ranged from 2 to 175 (mean: 41) months, with 63% of patients alive and well, 20% dead of disease, 13% alive with disease, and 3% dead from other causes. In the latter group (n=2), patients were 39 and 49 years old, one had tuberous sclerosis, while the other had pulmonary lymphangioleiomyomatosis. Both tumors expressed HMB-45, cathepsin K, and muscle markers, but lacked TFE3 and RAD51B rearrangements. The 2 patients are currently alive and well. Application of gynecologic-specific criteria (≥4 features required for malignancy: size ≥5 cm, high-grade atypia, mitoses >1/50 high-power fields, necrosis, and lymphovascular invasion) for predicting outcome misclassified 36% (4/11) of aggressive tumors; thus, a modified algorithm with a threshold of 3 of these features is recommended to classify a PEComa as malignant.

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

Perivascular epithelioid cell tumor (PEComa), mesenchymal tumors morphologically characterized by epithelioid cells, coexpress melanocytic and muscle markers. Herein, we describe a heretofore-undescribed tuberous sclerosis complex (TSC)-related neoplasm, morphologically resembling a soft tissue fibroma-like lesion, but showing an immunophenotype resembling PEComa. We identified 3 soft tissue fibroma-like lesions in individuals with TSC. We also evaluated 6 TSC-related periungual fibroma as well as a range of non-TSC fibroma-like lesions (n=19). Immunohistochemistry for HMB-45, desmin, smooth muscle actin, TFE3, and S100 was performed on the TSC-related fibromas. Periungual fibromas and non-TSC fibroma-like lesions were also stained for HMB-45. All 3 TSC patients were female, ranging in age from 4 to 51 years (mean, 26.7 y). Two tumors were located in extremities and 1 on the chest wall. The tumors showed elongated to stellate spindle-shape cells, prominent collagenous background, and lacked mitotic activity and cytologic atypia. Immunohistochemically, all 3 tumors were positive for HMB-45; smooth muscle actin or desmin was positive in both tumors tested. TFE3 was negative. All patients were alive with no evidence of disease with median follow-up of 55 months (range, 6 to 131 mo). Non-TSC fibroma-like lesions and oral and periungual fibromas were negative for HMB-45. Fibroma-like PEComa, a newly recognized soft tissue tumor with a strong association with TSC, mimics soft tissue fibroma but shows reactivity with melanocytic markers.

Malignant perivascular epithelioid cell tumor of the oropharynx with strong TFE3 expression mimicking alveolar soft part sarcoma: a case report and review of the literature.

Perivascular epithelioid cell tumors (PEComas) in the head and neck region are rare, with 26 cases described in literature. These distinct mesenchymal tumors normally express both myoid and melanocytic markers. We here report an interesting and challenging case of malignant PEComa that showed transcription factor E3 (TFE3) protein expression and rearrangement, paucity of muscle and melanocytic marker expression, and morphologically mimicked alveolar soft part sarcoma. Awareness of this morphologic pitfall and recognition of TFE3 gene-rearranged PEComa, as a distinct subtype of PEComa, is essential to avoid misdiagnosis.

t(6;11) renal cell carcinoma: a study of seven cases including two with aggressive behavior, and utility of CD68 (PG-M1) in the differential diagnosis with pure epithelioid PEComa/epithelioid angiomyolipoma.

Renal cell carcinomas with t(6;11) chromosome translocation involving the TFEB gene are indolent neoplasms which often occur in young patients. In this study, we report seven cases of renal cell carcinoma with TFEB rearrangement, two of whom had histologically proven metastasis. Patients (4F, 3M) ranged in age from 19 to 55 years (mean 37). One patient developed paratracheal and pleural metastases 24 months after surgery and died of disease after 46 months; another one recurred with neoplastic nodules in the perinephric fat and pelvic soft tissue. Histologically, either cytological or architectural appearance was peculiar in each case whereas one tumor displayed the typical biphasic morphology. By immunohistochemistry, all tumors labelled for cathepsin K, Melan-A and CD68 (KP1 clone). HMB45 and PAX8 staining were detected in six of seven tumors. All tumors were negative for CD68 (PG-M1 clone), CKAE1-AE3, CK7, CAIX, and AMACR. Seven pure epithelioid PEComa/epithelioid angiomyolipomas, used as control, were positive for cathepsin K, melanocytic markers, and CD68 (PG-M1 and KP1) and negative for PAX8. Fluorescence in situ hybridization results showed the presence of TFEB gene translocation in all t(6;11) renal cell carcinomas with a high frequency of split TFEB fluorescent signals (mean 74%). In the primary and metastatic samples of the two aggressive tumors, increased gene copy number was observed (3-5 fluorescent signals per neoplastic nuclei) with a concomitant increased number of CEP6. Review of the literature revealed older age and larger tumor size as correlating with aggressive behavior in these neoplasms. In conclusion, we present the clinical, morphological and molecular features of seven t(6;11) renal cell carcinomas, two with histologically demonstrated metastasis. We report the high frequency of split signals by FISH in tumors with t(6;11) chromosomal rearrangement and the occurrence of TFEB gene copy number gains in the aggressive cases, analyzing either the primary or metastatic tumor. Finally, we demonstrate the usefulness of CD68 (PG-M1) immunohistochemical staining in distinguishing t(6;11) renal cell carcinoma from pure epithelioid PEComa/epithelioid angiomyolipoma.

Melanotic PEComa of the Sinonasal Mucosa With NONO-TFE3 Fusion: An Elusive Mimic of Sinonasal Melanoma.

Perivascular epithelioid cell neoplasms (PEComas) are a family of mesenchymal tumors with features of both smooth muscle and melanocytic differentiation, with or without true melanin pigment. The highly variable morphology of PEComas results in a broad differential diagnosis that is also dependent on anatomic site. A subset demonstrates rearrangements involving the TFE3 (Xp11) locus, which can be used in diagnostically difficult cases. Here we describe a case of a melanotic PEComa with NONO-TFE3 fusion occurring in the sinonasal mucosa, as demonstrated by both next-generation sequencing and molecular cytogenetic studies. This case is the first of its kind in the literature and only the second documented PEComa harboring a NONO-TFE3 rearrangement. In light of unequivocal molecular ancillary studies, this case illustrates that PEComa must enter the differential for pigmented lesions of the sinonasal mucosa, where malignant melanoma would be much more likely to occur.

Alveolar Soft Part Sarcoma of the Female Genital Tract: A Morphologic, Immunohistochemical, and Molecular Cytogenetic Study of 10 Cases With Emphasis on its Distinction From Morphologic Mimics.

Alveolar soft part sarcoma (ASPS) is a morphologically distinctive neoplasm of unknown differentiation that bears a characteristic gene fusion involving ASPSCR1 and TFE3. ASPS can occur in the female genital tract, but is rare. Eleven cases with an initial diagnosis of ASPS at female genital tract sites were evaluated for their morphologic features and immunoprofile using a panel of antibodies (TFE3, HMB45, melan-A, smooth muscle actin, desmin, and h-Caldesmon). In addition, the presence of TFE3 rearrangement and subsequent ASPSCR1-TFE3 fusion were determined by fluorescence in situ hybridization. Ten tumors retained their classification as ASPS based on their morphologic appearance, immunohistochemical profile, and demonstration of ASPSCR1-TFE3 fusion. The remaining case was reclassified as conventional-type PEComa due to its pattern of HMB45, melan-A, and desmin positivity as well as absence of TFE3 rearrangement. Sites of the 10 ASPS were uterine corpus (3), cervix (2), uterus not further specified (2), vagina (2), and vulva (1). The age of the patients ranged from 15 to 68 years (mean 34 y, median 32 y). The tumors demonstrated a spectrum of morphologic features, but all had a consistent immunophenotype of strong TFE3 nuclear expression and lack of muscle (smooth muscle actin, desmin, h-Caldesmon) and melanocytic (melan-A, HMB45) markers, except focal positivity for HMB45 in 1. Follow-up was available for 4 patients ranging from 1 to 35 months (mean 15 mo, median 25 mo) and they were alive and had no evidence of recurrence or metastasis at last follow-up. Distinguishing ASPS from its morphologic mimics, particularly PEComa, is important due to increasingly efficacious targeted agents such as MET-selective and VEGF signaling inhibitors in the former and mTOR inhibition therapy in the latter.

Hepatic perivascular epithelioid cell tumor in three patients.

Perivascular epithelioid cell tumor (PEComa) is a rare, soft tissue tumor that can occur in various locations. The present report included three patients (one male and two females; age range, 25-51 years) with hepatic PEComas. The collected data included the clinical manifestations, diagnosis, management, treatment, and prognosis. Since it is difficult to diagnose hepatic PEComas by imaging, the patients were diagnosed by tumor tissue examination such as immunohistochemistry, which was positive for HMB-45, Melan-A, and SMA on all slides. The tumor was composed of diverse tissues including smooth muscle, adipose tissue, and thick-walled blood vessels. During the follow-up period, one of the tumors was malignant (double-positive for CD34 and Ki-67) and recurred 3 months after surgery. In addition, malignant hepatic PEComas were reviewed in the literature, indicating that the majority of hepatic PEComas are benign, but few hepatic PEComas exhibit malignant behaviors in older female patients (>50 years of age) with abdominal discomfort and pain, larger tumor size (>10 cm), or positive staining for CD34 and Ki-67. In conclusion, there is no effective method to diagnose PEComas. Currently, the diagnosis of PEComas depends on immunohistochemical staining. Tumor resection and close follow-up are the principal methods for the management of PEComas.

Intrahepatic peribiliary perivascular epithelioid cell tumor (PEComa) associated with heterotopic pancreas: A case report.

BACKGROUND: Perivascular epithelioid-cell tumor (PEComa) is a group of rare mesenchymal neoplasms that express myomelanocytic-cell markers and exhibit a wide variety of histopathological features. Although heterotopic pancreas has been reported to occur in the gastrointestinal tract, intrahepatic heterotopic pancreas has been reported only rarely. CASE PRESENTATION: We present a case of intrahepatic PEComa that showed a strong regional correlation with the presence of heterotopic pancreas. An intrahepatic tumor and biliary dilatation was incidentally discovered during a diagnostic evaluation to investigate low-back pain in a 47-year-old Japanese male. Cholangiocarcinoma was suspected and a left hemihepatectomy performed. Histological examination revealed a 3 × 3.8-mm tumor in the neighboring B2 bile duct. Histological and immunohistochemical investigations revealed the presence of a PEComa and pancreatic acini within the tumor mass. PEComa in the hepatobiliary and pancreatic regions are extremely rare. The presence of heterotopic pancreas is also relatively uncommon. CONCLUSION: The strong regional association of these 2 lesions raises the possibility of a PEComa originating from heterotopic pancreas or from an irritable response caused by heterotopic pancreas.

Pancreatic perivascular epithelioid cell tumor: A case report with clinicopathological features and a literature review.

Perivascular epithelioid cell tumor (PEComa) of the pancreas is an unusual tumor deriving from mesenchyma. This paper described a case of pancreatic PEComa, which was initially suspected as neuroendocrine carcinoma by biopsy, and therefore surgical treatment was recommended due to undetermined diagnosis. Examination of the surgical specimen under a microscope showed that the tumor cell's morphology was epithelioid or spindle-shaped, and ranged in a nested pattern. Additionally, these cells had a large extent of acidophilic cytoplasm, no mitotic figures, and expressed HMB-45, melan-p, and smooth muscle actin immunohistochemically. Pathological examination indicated that PEComa originated from the pancreas, but symptoms related to tuberous sclerosis were absent. Since PEComa is extremely rare in the pancreas, it is likely to be ignored in differential diagnosis. In conclusion, our article highlighted the clinicopathological features of PEComa, and we conducted a literature review focusing on PEComa so as to deepen the understanding of this tumor type.

Ruptured pericardial perivascular epithelioid cell tumor (PEComa) leading to sudden death: an autopsy case report and review of the literature.

A 30-year-old man with past medical history of atrial fibrillation/flutter passed away after presenting with sudden-onset cardiac dysfunction. The postmortem examination revealed cardiac tamponade secondary to rupture of a 7.2-cm pericardial perivascular epithelioid cell tumor (PEComa). The tumor grossly appeared to arise from the transverse pericardial sinus and focally penetrated the epicardium of the right atrium. Microscopically, it was composed of predominately spindle cells with low nuclear grade, no pleomorphism, or readily apparent mitoses. Immunohistochemistry revealed cytoplasmic reactivity for HMB-45, desmin, and smooth muscle actin. Electron microscopic findings were characterized by melanosome-like structures intermixed with intermediate filaments and abundant stacked endoplasmic reticulum. The present case is unique among previously reported pericardial/myocardial PEComas as a first example resulting in unexpected cardiac tamponade and sudden cardiac death.