Sclerosing variant of epithelioid angiomyolipoma

Presented herein are two unusual epithelioid angiomyolipomas (AML) displaying prominent stromal sclerosis. Both patients were middle-aged women without a clinical history of tuberous sclerosis. One patient (case 1) had a 2 cm lesion arising in the renal cortex, and another (case 2) had a pararenal retroperitoneal tumor measuring 13 cm. Both tumors were composed of sheets or nests of polygonal epithelioid or short spindle cells having uniform round to oval nuclei and eosinophilic cytoplasm with cords of hyalinized sclerotic stroma between them. The tumor in case 2 had small areas of mature-looking fat cells. Immunohistochemically, epithelioid tumor cells were diffusely positive for actins and desmin in both cases, and melanoma antigen recognized by T cells (MART)-1 was positive in patient 2. Scattered HMB-45-immunoreactive cells were identified in the sclerotic cords of both tumors, but epithelioid tumor cells were essentially negative for HMB-45. The characteristic clinicopathological and immunohistochemical features of the present cases are analogous to a subset of epithelioid AML or sclerosing perivascular epithelioid cell tumors previously reported.     

Malignant perivascular epithelioid cell tumor of the retroperitoneum

Perivascular epithelioid cell tumors (PEComas) are a rare type of mesenchymal neoplasms characterized by a proliferation of perivascular cells with an epithelioid phenotype and expression of myo-melanocytic markers. The majority of PEComas seem to be benign and usually their prognosis is good. Malignant cases are extremely rare, exhibiting a malignant course with local recurrences and distant metastases. We herein report a case of a malignant PEComa arising in the retroperitoneum. The patient was a 55-year-old woman experiencing abdominal discomfort for approximately one month. Ultrasound and computer tomography (CT) scans of the abdomen revealed a solid mass arising from the retroperitoneum. Microscopically, the tumor was composed of epithelioid cells mixed with spindled cells. The nucleus had significant atypia, and the mitoses were obvious. The focal intravascular tumor embolus was visible. Immunohistochemically, the epithelioid tumor cells were positive for HMB45 and Melan-A, and the spindled tumor celLs were positive for SMA and desmin. Seven months after a surgical resection, an ultrasound revealed liver metastases. In conclusion, the malignant PEComas of the retroperitoneum is a very rare neoplasm with unique morphological and immunohistochemical characteristics. It should be differentiated from other epithelioid cell tumors of the retroperitoneum.     

Incidental perivascular epithelioid cell tumor in an inguinal hernia sac

Perivascular epithelioid tumors (PEComa) are uncommon mesenchymal neoplasms demonstrating positivity for muscular and melanocytic immuno-markers. Included in this category are angiomyolipoma, lymphangioleiomyomatosis, and clear cell sugar tumors. Lesions which do not fit into these categories are classified as “not otherwise specified”. We present a case of an incidentally discovered PEComa within inguinal hernia sac contents in a 70-year-old woman. It consisted of spindled and epithelioid cells with bland oval nuclei, small nucleoli and clear to light eosinophilic cytoplasm. There was no atypia or mitoses. The lesion was strongly positive for HMB45 and smooth muscle actin. Pelvic soft tissue and peritoneal PEComas are rarely reported in literature and very little is known about their prognosis. We discuss the immunohistochemistry, differential diagnosis, and pathogenesis of PEComas.     

Minute perivascular epithelioid cell (PEC) nests in the abdominal lymph nodes—a putative precursor of PEComa

A perivascular epithelioid cell tumor (PEComa) is a peculiar growth defined as a mesenchymal tumor composed of histologically and immunohistochemically distinct perivascular epithelioid cells (PECs). Because neither normal counterparts nor precursor lesions of PEComa have been identified, we examined minute PEC nests, ranged from 0.8 mm to 10 mm, to investigate the possible origin of the PEComa. We examined a total of 80 677 para‐aortic and pelvic lymph nodes that were systematically dissected from 1656 patients for gynecological malignancies. The identified lesions were confirmed immunohistochemically with multiple PEC markers, including smooth muscle actin, HMB45, melan‐A, MiTF, ER and PgR. A total of 66 minute PEC nests were found in 21 patients (1.3% of the total population) with an average frequency of 3.1 lesions per patient. In cases of multiple involvement, 11 of 13 nests were located at the same level of multiple lymph node or on continuous levels. The lesions were preferentially distributed at the level of para‐aortic and high pelvic lymph nodes. All nests were positive for actin and HMB45, whereas the other markers were positive with varying frequencies. The minute PEC nests may be associated with the possible normal counterpart of PEComas.     

Malignant uterine perivascular epithelioid cell tumor: histopathologic and immunohistochemical characterization of a rare tumor in a post-menopausal woman

Background: Perivascular epithelioid cell tumors (PEComas) are rare, mesenchymal neoplasms composed of epithelioid cells exhibiting myogenic and melanocytic differentiation. The uterus is an infrequent site of involvement. The most common histopathologic mimics include leiomyosarcoma, endometrial stromal sarcoma, undifferentiated uterine sarcoma, and malignant melanoma. Rendering an accurate histopathologic diagnosis is essential, owing to the prognostic and therapeutic implications. Case: A 65-years-old post-menopausal woman presented with post-menopausal bleeding, abdominal pain, and heaviness for the last four months. Ultrasound abdomen revealed a large uterine mass replacing the endometrial cavity. She underwent a total abdominal hysterectomy with bilateral salpingo-oophorectomy. Result: Microscopically, a circumscribed tumor with tumor cells arranged in sheets and interlacing fascicles, with interspersed fine capillary network, was seen. The individual tumor cells were epithelioid to spindle with moderate pleomorphism, round nuclei, vesicular chromatin, prominent macronucleoli, and moderate cytoplasm. Mitosis was 2-3/50 HPFs. On immunohistochemistry, tumor cells were positive for HMB-45, Melan-A, and smooth muscle actin and were negative for h-caldesmon, TFE3, S-100, CD10, and pan-cytokeratin. Based on the histopathologic and immunohistochemical features, a final diagnosis of malignant uterine PEComa was rendered. Conclusions: This index report describes the characteristic histopathologic and immunohistochemical features of malignant uterine PEComa and highlights the salient features that distinguish it from other commonly encountered histopathologic mimics.     

血管周上皮样细胞肿瘤的分子遗传学

血管周上皮样细胞肿瘤(perivascular epithelioid cell tumours,PEComas)是由组织学和免疫组织化学上有独特表现的血管周上皮样细胞构成的间叶性肿瘤,PEComas家族包括肾血管平滑肌脂肪瘤、肺透明细胞"糖"瘤、淋巴管肌瘤病、淋巴管平滑肌瘤、镰状韧带透明细胞肌黑色素细胞性肿瘤和其他部...     

Malignant perivascular epithelioid cell tumor of the colon: report of a case with molecular analysis

Perivascular epithelioid cell tumor (PEComa) is a rare mesenchymal neoplasm, and malignant cases are extremely rare. A case of malignant PEComa arising in the colon is described herein. The patient was a 43-year-old Japanese woman without a history of tuberous sclerosis complex. The tumor occurred in the abdominal cavity attached to the serosal side of the descending colon. Histologically, the tumor consisted of sheets or closely packed nests of epithelioid cells with clear or eosinophilic cytoplasms. The tumor cells were positive for HMB-45 but negative for S-100 protein and cytokeratins by immunohistochemical staining. Ki-67 labeling index was 2.9%. Peritoneal dissemination of tumor occurred at 20 months and the patient died of tumor at 38 months after the initial operation. This was considered to be a case of malignant PEComa, based on the histological and clinical features. Tumor cells showed overexpression of cyclin D1 but lacked the loss of heterozygosity of the TSC1 and TSC2 genes. The result suggests that the overexpression of cyclin D1 may play an important role in the tumorigenesis of PEComa. Because PEComas can behave in an aggressive manner, careful follow up is warranted.     

Primary perivascular epithelioid cell tumor in the rectum: A case report and review of the literature

Perivascular epithelioid cell tumor (PEComa) is a rare collection of tumors arising in a wide array of anatomic locations. It is characterized by the presence of a peculiar population of myomelanocytic marker-positive perivascular epithelioid cells, and is commonly detected in the uterus. The colorectal area is an uncommon site for primary PEComa. In this study, we describe a 17-year-old patient presenting with a rectal polyp. Histologically, the tumor consisted of sheets of round to polygonal epithelioid cells with clear and granular cytoplasm, and a prominent capillary network. Some of the tumor cells were positive for Fontana-Masson staining. Immunohistochemically, the tumor cells were positive for HMB-45, and were negative for cytokeratin, vimentin, S-100 protein, actin, desmin, EMA, CD34, and c-kit. After finding melanosomes or premelanosomes at the ultrastructural level, the diagnosis of PEComa was made. Although PEComa arising within the intestinal tract is unusual and clinically unexpected, PEComa should be considered in the differential diagnosis of rectal polypoid lesions.     

Perivascular epithelioid cell tumour (PEComa) of the soft tissue

AIMS: PEComa is a rare tumour developing from perivascular epithelioid cells (PEC) and is characterised by positive immunoreactivity for HMB45. Since PEComas are tumours having both a spindle cell component and an epithelioid and giant cell component, as seen in many sarcomas, as well as having a wide distribution in various organs and soft tissue, we reviewed cases originally diagnosed as sarcomas of the soft tissue in our institution and screened them by immunostaining for HMB45. METHODS: Consecutive soft tissue sarcomas (31 tumours) retrieved from the Surgical Pathology file at our institution for a period of 3 years were submitted for immunostaining for HMB45. Cases with positive HMB45 immunostaining were submitted for further immunostaining for MART1, CD68, S100 protein, cytokeratin AE1/3, EMA, vimentin, MSA and CD117. RESULTS: Of 31 sarcomas, three tumours in the group of 11 malignant fibrous histiocytomas (MFH) and unclassified sarcomas showed positive immunoreactivity for HMB45 and MART1 in 1-25% of tumour cells. The three tumours were located in the lower extremities and measured 8, 11 and 12 cm in diameter. Patient gender male:female was 2:1 and ages were 46, 56 and 60 years. Microscopically, the tumours were composed of a variable proportion of spindled cells, multinucleated cells and epithelioid cells disposed in diffuse sheets or nests. Mitotic figures and necrosis were frequent. The immunoreactivity was diffuse for CD68, focal for AE3 and EMA, negative or focal for MSA and CD117, and negative for S100 and AE1. All three patients developed lymph node or distant metastases and died of the disease within 1-2 years. CONCLUSIONS: PEComa re-screened from the group of high grade sarcomas without definite differentiation range from pleomorphic to monomorphic cytohistopathological features. Immunostaining for HMB45 of unclassified sarcomas is useful for the classification of these tumours. They occur preferentially in the lower extremities and have a high malignant potential when associated with large size, tumoural necrosis and high mitotic activity.     

Primary perivascular epithelioid cell tumor of the bladder

The perivascular epithelioid cell family of tumors includes angiomyolipoma, clear cell “sugar” tumor of the lung, lymphangioleiomyomatosis, and clear cell myomelanocytic tumor of the falciform ligament/ligamentum teres. Less frequently, perivascular epithelioid cell tumors arise in various other locations throughout the body including soft tissue, bone, and visceral organs. We report a case of a 23-year-old man who presented with 2-month history of frequent micturition and odynuria. Based on clinical examination, ultrasound computed tomography imaging, surgical operation, and histopathologic studies, a definitive diagnosis was made. Further characteristic images and pathology of this disease are discussed.     

Primary hepatic clear cell myomelanocytic tumor. Case report and review of the literature

A case of hepatic clear cell myomelanocytic tumor in a 31-year-old woman presenting clinically with abdominal pain is reported. Histopathologic examination showed a lesion characterized by a population of large epithelioid cells with clear or eosinophilic granular cytoplasm, rich in glycogen. Immunohistochemically, the tumor cells were positive for HMB-45, Melan-A and muscle-specific actin, but negative for epithelial markers, desmin, S-100 protein, and neuroendocrine markers. Ultrastructurally, the tumor cells had abundant glycogen, well-developed rough endoplasmic reticulum, microtubules and aberrant melanosomes. Clinical and pathologic features with a brief review of the relevant literature for hepatic CCMMT as a variant of perivascular epithelioid cell tumor (PEComa) are discussed.     

Perivascular epithelioid cell tumor of the pancreas: case report and literature review

Neoplasms with perivascular epithelioid cell differentiation (PEComas) of the pancreas are rare, and only 22 cases have been reported globally. Therefore, clinician and pathologist knowledge of this tumor’s biologic behavior and molecular genetics has been limited. A 40-year-old female patient presented with a space-occupying mass in the pancreas found by abdominal B-mode ultrasonography upon physical examination. Laparoscopic resection of the pancreatic body and tail was performed, and a cystic-solid tumor of about 2 × 2 cm was identified. PEComa is a type of mesenchymal tumor with uncertain biologic behavior, more frequently found in females. PEComa features a unique histomorphology and immunophenotype. We summarize the characteristics and research progress of the pancreatic PEComa, which will be convenient for physicians and pathologists to fully understand the disease to avoid misdiagnosis and to provide a reference for treatment and prognosis.     

Comparative genomic hybridization study of perivascular epithelioid cell tumor: molecular genetic evidence of perivascular epithelioid cell tumor as a distinctive neoplasm

Perivascular epithelioid cell tumor (PEComa) is a neoplasm composed chiefly of HMB-45-positive epithelioid cells with clear to granular cytoplasm and a perivascular distribution. Such tumors have been reported in different organs under a variety of designations. The cytogenetic features of these neoplasms have not been well studied. We collected 9 tumors (5 of kidney, 1 of prostate, 1 of urinary bladder, 1 of the pelvic cavity soft tissue, and 1 of uterus) from 8 patients, including one patient with tuberous sclerosis complex. The paraffin blocks of tumor tissue were submitted for comparative genomic hybridization analyses. Gross chromosomal aberrances were observed in all cases. The frequent imbalances were losses on chromosome 19 (8 cases), 16p (6 cases), 17p (6 cases), 1p (5 cases), and 18p (4 cases) and gains on chromosome X (6 cases), 12q (6 cases), 3q (5 cases), 5 (4 cases), and 2q (4 cases). The frequent deletion of 16p in which TSC2 gene is located indicates the oncogenetic relationship of PEComas with angiomyolipoma as a TSC2-linked neoplasm. From a molecular genetic perspective, the recurrent chromosomal alterations in both renal and extrarenal tumors further support the concept of PEComa as a distinctive tumor entity regardless of anatomic location.     

Heavily melanotic perivascular epithelioid clear cell tumor of the kidney

A black-colored and well-circumscribed renal tumor in a 71-year-old woman is reported. The tumor was unique in that it was rich in vasculature and exclusively composed of perivascular epithelioid clear cells. Morphological features were reminiscent of conventional renal cell carcinoma (RCC). However, immunohistochemical examinations showed that the tumor cells did not express any epithelial markers, but diffusely and intensely expressed a melanocytic marker, gp-100/HMB-45. Another striking feature of the tumor was a large amount of cytoplasmic pigment that made the tumor wholly black. The pigment was not stained with Berlin-blue, completely bleached with potassium permanganate, and stained with Fontana-Masson staining, which suggests that the pigment was melanin. Morphological features and immunohistochemical findings indicated that the present tumor was an extreme example of a perivascular epithelioid clear cell tumor with a large amount of melanin, which has not been previously reported. One should be aware of the pure form of perivascular epithelioid clear cell tumor of the kidney because it is sometimes very difficult to differentiate this tumor from conventional RCC. Immunohistochemical examinations and the presence of cytoplasmic melanin can help the differentiation.     

Perivascular epithelioid cell tumor of the uterine cervix identified on a conventional cervical smear

Perivascular epithelioid cell tumors (PEComas) most frequently involve the uterus, particularly the uterine corpus and very occasionally the cervix. One case of PEComa identified using a conventional cervical smear has previously been documented. Herein, we present the second such case. The patient was a 51‐year‐old woman with abnormal genital tract bleeding. Samples collected for conventional cervical smears were submitted for cytopathological examination, which revealed discohesive monotonous tumor cells showing epithelioid morphology, ample cytoplasm that was pale to weakly eosinophilic, and mildly enlarged nuclei. The cytopathological features were well correlated with histopathological findings. Upon immunohistochemistry, the tumor cells were positive for both melanocytic and smooth muscle markers. Based on these findings, PEComa was diagnosed. Subsequently, a total hysterectomy with bilateral salpingo‐oophorectomy was performed, revealing that the tumor (28 × 22 × 12 mm) was located at the superficial part of the endocervix. We propose that the cytopathological findings described herein can guide the diagnosis of PEComa, even though this tumor is rare. Diagn. Cytopathol. 2015;43:1011–1016. © 2015 Wiley Periodicals, Inc.     

Perivascular epithelioid cell tumor of the uterus: immunohistochemical, ultrastructural and molecular study

A case of perivascular epithelioid cell tumor of the uterus is reported, occurring in a 32-year-old woman. The tumor (8.0 cm in dimension) showed exophytic growth from the outer half of the myometrium. Histopathologically, the tumor was composed of thick blood vessels and perivascular epithelioid cells. The neoplastic cells were strongly immunoreactive for HMB45 antigen, CD117 (c-kit), vimentin and the progesterone receptor, but completely negative for S-100 protein, smooth muscle actin, desmin, CD34, the estrogen receptor and p16. The Ki-67 labeling index was low (1.25%). Ultrastructurally, the neoplastic cells had numerous premelanosomes with some glycogen deposits. Single-stranded DNA conformational polymorphism of p53 and methylation-specific polymerase chain reaction of p16 revealed negative results. Definite melanosomes on electron microscopic analysis and coexpression of HMB45 antigen and stem cell factor receptor (CD117) may provide the clue to understanding perivascular epithelioid cell tumor because angiomyolipoma also coexpresses HMB45 antigen and CD117.     

Sclerosing epithelioid fibrosarcoma: cytogenetic analysis of FUS rearrangement

Sclerosing epithelioid fibrosarcoma (SEF) is a rare but distinct variant of fibrosarcoma. A 43-year-old man presented with a lesion in his back that had been present for three years but had recently increased in size. Magnetic resonance imaging (MRI) revealed a 6-cm sized ovoid mass showing low intensities on T1 and T2 weighted images. Histologically, the tumor was of moderate cellularity, and the cells were relatively uniform in size and shape. The cells were epithelioid, round, oval and polygonal with clear and slightly eosinophilic cytoplasm, forming nests, cords, or sheet-like patterns with a dense collagenous and hyalinized matrix. The tumor was positive for vimentin, but negative for smooth muscle actin, desmin, HMB45, and CD34. Although the tumor showed nuclear overexpression of beta-catenin protein, the CTNNB1 exon3 mutation was not detected. Fluorescent in situ hybridization for FUS using dual color break-apart probes showed rearrangement of the FUS. In accordance with previous studies, our case showed positive findings of FUS rearrangement, reinforcing the notion of a close relationship between low grade fibromyxoid sarcoma and SEF.     

具有血管周上皮样细胞分化的肿瘤15例临床病理分析

目的探讨具有血管周上皮样细胞分化的肿瘤(perivascular epithelioid cell tumor,PEComa)临床病理特征及免疫表型。方法对15例PEComa行EnVision两步法免疫组化及特殊染色,并分析其临床表现、病理学特征和免疫组化特点。结果 15例PEComa中13例为女性,且术后无复发。肿瘤可发生在身体任何部位,以肝脏和肾脏最多见,有包膜,多为实性,可有出血。特征性组织学改变是肿瘤细胞围绕血管生长。PAS染色显示该肿瘤细胞中有糖原物质沉积,弹力纤维染色显示该肿瘤中的血管壁缺乏弹力层。免疫组化显示所有PEComa病例均明显表达HMB-45、Melan-A、SMA,Ki-67阳性率低。结论 PEComa是一组具有恶性潜能的肿瘤,多发于女性,来源于血管周上皮样细胞。大部分肿瘤呈良性过程,生物学分级极低,预后良好;极少部分病例可发生转移,预后不佳。免疫组化检测对其组织来源、生物学行为具有提示意义,并可辅助诊断。     

Malignant perivascular epithelioid cell tumor of the kidney with rare pulmonary and ileum metastases

Aims: To report one case of malignant perivascular epithelioid cell tumor (PEComa) of the kidney with rare pulmonary and ileum metastases and analyze its clinicopathological features. Methods: We analyzed the clinicopathological features of one case of malignant PEComa of the kidney with pulmonary and ileum metastases. Immunohistochemistry staining was performed. Results: The patient was a 48-year-old man with a renal mass approximately 14 cm × 11 cm × 8 cm in size. Microscopically, the tumor was mainly composed of polygonal epithelioid cells with dense eosinophilic cytoplasm and round nuclei with small nucleoli. Focal tumor cells showed pleomorphism with multinucleated giant cells and prominent nucleoli. The tumor cells nests were surrounded by thick-walled irregular blood vessels. Focal fat cells were found within the tumor. Hemorrhage and coagulative necrosis were also present. The tumor cells were positive for vimentin, HMB45, and Melan-A, and focally positive for SMA and S-100 protein. After 5 years and 5.6 years of nephrectomy, the tumor metastasized to the right lung and ileum, respectively. Conclusion: We first reported one case of malignant PEComa of the kidney with pulmonary and ileum metastases. Metastatic PEComa of the lung and ileum should differentiate from primary carcinoma, metastatic carcinoma, malignant melanoma, and gastrointestinal stromal tumor.