Primary cutaneous PEComa: distinctive clear cell lesions of skin

PEComa-its clinical features, histopathology, and current therapy

Perivascular epithelioid cell tumors (PEComas) are a rare family of mesenchymal tumors that includes angiomyolipoma, lymphangioleiomyomatosis, pulmonary clear cell "sugar" tumors, and PEComa-not otherwise specified. This study aimed to provide a comprehensive review of the clinical features, molecular biology, and current status of PEComa treatment. It reportedly occurs at several sites, including the uterus, kidney, liver, lung, abdominopelvic soft tissue, gastrointestinal organs, retroperitoneum, soft tissue, bone, and skin. More common in women, it occurs in young to middle-aged people. Although the disease generally follows a benign course, cases of malignant PEComa have been reported. Malignant PEComa is characterized by a large tumor size, a high mitotic rate, and the presence of necrosis and nuclear atypia. Immunohistochemically, PEComas typically express melanocytic markers such as human melanoma black 45 (HMB45) and melanoma antigen (melan-A) and muscle markers such as smooth muscle actin (α-SMA), desmin, and caldesmon. More recently, a subtype of PEComa harboring TFE3 gene rearrangement that is mutually exclusive with tuberous sclerosis complex (TSC) mutations has been identified. The identification of TFE3 gene rearrangement can help confirm the diagnosis. The distinctive features of these TFE3-rearranged PEComas include a young-age tendency, the absence of an association with tuberous sclerosis, predominant alveolar architecture and epithelioid cytology, minimal immunoreactivity for muscle markers, and strong (3+) TFE3 immunoreactivity. Surgery is the curative treatment of choice; however, there are reports of cases and randomized controlled trials showing the efficacy of mTOR inhibitors. To the best of our knowledge, there are no reports of radiation therapy's efficacy.

Perivascular epithelioid cell tumors (PEComas) of the bone and soft tissue: a Japanese Musculoskeletal Oncology Group (JMOG) multi-institutional study

PURPOSE

Perivascular epithelioid cell tumors (PEComas) of the bone and soft tissues are rare mesenchymal neoplasms, some of which are malignant. However, their clinical and pathological characteristics remain unclear. This study was performed to investigate the clinical and pathological characteristics of PEComas in bone and soft tissues by leveraging information from the Japanese Musculoskeletal Oncology Group.

METHODS

Nine patients, including four male and five female patients with a median age of 50 years, were retrospectively reviewed. PEComas of the visceral organs, including the uterus and retroperitoneum, were excluded.

RESULTS

Eight tumors arose in the soft tissue and one in the bone, with a mean size of 8.8 cm. Four patients showed local recurrence or distant metastasis. The 1-year survival rate was 78%. Pathologically, eight tumors were classified as malignant and one as having uncertain malignancy potential. Half of the tumors showed high MIB-1 index values of > 30%. Immunohistochemically, the melanocyte marker HMB45 was expressed in 89% of the cases, and muscle-specific markers were expressed only in 30-50% of the cases. Transcription factor binding to IGHM enhancer 3 (TFE3) expression was positive in 100% of the patients. Tumors with high expression of TFE3 were classified as PEComas with malignant potential according to Folpe's classification.

CONCLUSIONS

Bone and soft tissue PEComas may have a higher malignancy potential than other visceral PEComas and are more likely to develop as TFE3-rearranged PEComas.

Metastatic melanoma and rare melanoma variants: a review

The histopathological diagnosis of melanoma is fraught with potential pitfalls. In the setting of cutaneous metastatic melanoma, it is important to recognise the various histological patterns that can be encountered from the more common to the rare, including epidermotropic, folliculotropic, naevoid, and blue naevus-like. In addition, melanoma is notorious for phenotypic plasticity. Thus, there are many different subtypes and cytomorphological variations that can be difficult to recognise as melanoma, particularly in the recurrent or metastatic setting. Select melanoma variants including primary dermal, clear cell, plasmacytoid, signet ring cell, small cell, myxoid, rhabdoid, and dedifferentiated melanoma will be discussed, in addition to composite melanocytic neoplasms. This review is intended to remind the practitioner of key concepts of metastatic disease and select rare melanoma variants, while providing practical guidelines for accurate diagnosis.

Perivascular Epithelioid Cell Tumor (PEComa) of the Pancreas in a Patient with Ulcerative Colitis: A Case Report and Review of the Literature

Perivascular epithelioid cell tumors (PEComas) are mesenchymal tumors of peculiar cells that are focally associated with blood vessels, and generally have a distinctive bi-phenotypic expression of both smooth muscle and melanocytic markers. There are several entities in the PEComa family, including tumors that arise in the soft tissues and viscera. Frequently affected organs include the lungs (sugar tumors), uterus, broad ligament, colon, small bowel, liver, and pancreas. Ulcerative colitis (UC) has been associated with the development of tumors, especially colorectal and hepatobiliary carcinomas. Rare cases of UC have been reported in the PEComa family of tumors, but none in the pancreas. Here, we present a case study of a 27-year-old female patient with a history of UC who developed PEComa of the pancreas, a unique association that has not been previously reported. We also review reported cases of PEComas in the pancreas, as well as PEComas at all anatomic sites associated with UC.

Cutaneous Angiomyolipoma-A Distinct Entity That Should Be Separated From Classic Angiomyolipoma: Complete Review of Existing Cases and Defining Fundamental Features

Cutaneous angiomyolipoma is a rare mesenchymal tumor that is demographically, clinically, and immunohistochemically distinct from its renal and extrarenal counterparts. We present a case of cutaneous angiomyolipoma in the right retroauricular area of a 35-year-old male patient and provide a broad systematic review of the literature and the largest compilation of cutaneous angiomyolipomas reported to date. According to the findings presented in this review, we conclude that cutaneous angiomyolipoma should be completely separated from renal and extrarenal angiomyolipomas and therefore be considered a distinct entity in the classification of skin tumors.

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.

Nevus, melanoma or something else? Mesenchymal neoplasms with melanocytic differentiation

The overwhelming majority of cutaneous neoplasms with melanocytic differentiation are nevi, melanomas and more rarely melanocytomas. Nevertheless, there is also a group of mesenchymal neoplasms with genuine melanocytic differentiation which can create diagnostic difficulties with significant repercussions. These can rarely present as primary or metastatic cutaneous lesions. Theones that are relevant to a dermatopathologist include malignant melanotic nerve sheath tumor, perivascular epithelioid cell neoplasm and clear cell sarcoma. This work will provide a thorough review of clinical presentation, morphologic and immunohistochemical features as well as molecular pathogenesis of these tumors. We hope to familiarize the general dermatopathology readership with a group of neoplasms of mesenchymal lineage exhibiting melanocytic differentiation and ultimately avoid diagnostic misadventures. This article is protected by copyright. All rights reserved.

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.

Clear Cell Tumor With Melanocytic Differentiation and ACTIN-MITF Translocation: Report of 7 Cases of a Novel Entity

Clear cell morphology is an uncommon finding in tumors. A subset of clear cell neoplasms also shows melanocytic differentiation, including clear cell sarcoma, PEComa, and some subtypes of renal cell carcinoma. A hallmark of these tumor types is the activation of a member of the MIT/TFE family of transcription factors, which includes MITF, TFE3, TFEB, and TFEC. Microphthalmia transcription factor (MITF is the master regulator of melanin synthesis, while TFEB plays a critical role in lysosome biogenesis. Cytogenetic translocations involving TFE3 and TFEB are now well described in multiple tumor types, but there has been little evidence to suggest similar regulation of MITF. Here we describe a series of 7 clear cell cutaneous neoplasms with melanocytic differentiation that are characterized by ACTIN-MITF gene fusions, either ACTB-MITF or ACTG1-MITF. The chromosomal breakpoints preserve MITF's dimerization and transcriptional activation domains, suggesting that these fusion proteins likely result in hyperactive MITF function, analogously to the previously reported TFE3 and TFEB fusions. Our findings indicate that MITF gene rearrangements may be key drivers of tumor pathogenesis and expand the spectrum of neoplasia associated with the MIT/TFE family.

CD10-Positive Cutaneous PEComa: An Extremely Rare Skin Tumour

We here present the case of a 67-year-old woman with a history of a slowly progressive, polypous nodule on her left wrist. The lesion was excised, and the histological analysis revealed a clear cell tumour that was relatively sharply demarked from the surrounding tissue extending into the subcutaneous tissue. The tumour showed a characteristic trabecular pattern in which the tumour cells were arranged around numerous vessels. The neoplastic cells had a predominantly epithelioid shape, granular eosinophilic to clear cytoplasm and prominent centrally located nucleoli. The histological differential diagnosis included a metastatic clear-cell renal cell carcinoma and a primary cutaneous perivascular epithelioid cell tumour (PEComa). Immunohistochemically, the tumour cells revealed homogenous expression of HMB-45, MiTF and CD10, whereas MART-1 and S100 were negative. Antibodies against actin marked the trabecularly arranged vessels, and the neoplastic cells yielded a patchy positivity against actin and desmin. Additional immunohistochemical stains against pan-cytokeratin, CAIX, PAX-8 and EMA were negative. Based on the morphologic and immunophenotypic findings, the histological diagnosis of a CD10-positive cutaneous PEComa was made.

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.

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.

Cutaneous Angiomyolipoma of the Ear: A Case Report and Literature Review

Cutaneous angiomyolipoma is a rare mesenchymal tumor, distinct from its renal counterpart. Only few cases have been reported in English language literature to date. Here, we report a case in a 36-year-old man who presented with a painless swelling on his right ear. Microscopy revealed a well-circumscribed tumor, composed of an admixture of mature adipocytes, blood vessels, and bundles of smooth muscles. The tumor cells were positive for desmin and calponin but negative for HMB45, melan-A, SOX10, tyrosinase, and CD10. We present the case to emphasize the uniqueness of cutaneous angiomyolipoma from its renal counterpart. We also review the relevant literature on this topic.

A rare case of perivascular epithelioid cell tumor (PEComa) of the greater omentum

Background

A tumor composed exclusively or predominantly of human melanin black 45 (HMB45)-positive epithelioid cells is called a perivascular epithelioid cell tumor (PEComa). We report a very rare case of a PEComa of the greater omentum.

Case presentation

MRI conducted to examine the orthopedic disease of the patients, a 49-year-old Japanese woman, also identified a tumor in her pelvis. A CT scan revealed a tumor mass on the right side of the pelvic floor and clear nutrient vessels originating from the splenic and celiac arteries. An omental primary tumor or accessory spleen was thus suspected, and tumor resection was performed. The tumor was a light brown solid tumor with a smooth margin, measuring 5.2 × 3.8 × 3.5 cm. Histopathologically, the tumor was composed mainly of spindle and epithelioid cells, and large and small blood vessel formation was observed. In the immunohistochemical staining, tumor cells were positive for human melanin black 45 (HMB-45) and Melan-A and partially positive for alpha-smooth muscle actin. The final diagnosis was PEComa of the greater omentum.

Conclusions

Although omental PEComa is very rare, it should be considered as a differential disease of an omental primary tumor.

Soft Tissue Tumors of Uncertain Histogenesis: A Review for Dermatopathologists

The mesenchymal tumors discussed herein represent a heterogeneous group of neoplasms with distinctive morphologic, immunophenotypic, and molecular genetic features. These uncommon tumors often arise in the dermis and subcutis and can pose a major diagnostic challenge to dermatopathologists because they closely mimic melanoma, carcinoma, fibrous histiocytoma, schwannoma, or granulomatous inflammation. This article reviews the clinical presentation, histopathology, differential diagnosis, and diagnostic pitfalls of epithelioid sarcoma, clear cell sarcoma, perivascular epithelioid cell tumor, ossifying fibromyxoid tumor, pleomorphic hyalinizing angiectatic tumor, and hemosiderotic fibrolipomatous tumor. Associated molecular genetic findings are also briefly reviewed with an emphasis on their diagnostic usefulness.

Primary cutaneous perivascular epithelioid cell tumor (PEComa): Five new cases and review of the literature

PEComas represent a family of uncommon mesenchymal tumors composed of "perivascular epithelioid cells" with a distinct immunophenotype that typically shows both myogenic and melanocytic differentiation. The PEComa family includes angiomyolipoma (AML), clear cell "sugar" tumor of the lung and extra pulmonary sites, lymphangioleiomyomatosis and clear cell myomelanocytic tumor of the falciform ligament/ligamentum teres. Very rarely, PEComas may arise in the skin. Primary cutaneous PEComas typically display a dermal proliferation of epithelioid cells with pale, clear, or granular pink cytoplasm arranged in nests and trabecula with an intervening arborizing network of delicate capillaries. Primary cutaneous PEComas have a lower frequency of myogenic marker expression than their deep soft tissue and visceral counterparts. They also often express strong diffuse CD10, leading to potential confusion with metastatic renal cell carcinoma. Most cases behave indolently. We report 5 additional cases of this rare entity. All showed classic histologic features and expression of either HMB-45 and/or Melan-A/MART-1. Four cases were tested for myogenic markers (2 were positive & 2 were negative). Three cases were tested for CD10 (all 3 were positive). All of our cases with clinical follow-up behaved indolently. Table 1 provides a summary of findings for all 5 cases in our series.

Pigmented perivascular epithelioid cell tumor of the skin: first case report

The authors present a first case of pigmented perivascular epithelioid cell tumor (PEComa) of the skin, which was misdiagnosed histopathologically as metastatic melanoma. PEComa are exceedingly rare neoplasms, and only a few cases have been reported in kidney, liver, and pelvis. Herein, we describe this very rare entity in the subcutaneous tissue of the flank with very similar if not identical morphology of renal clear cell carcinoma. Because of the presence of focal melanin pigmentation and strong positivity for HMB-45, the lesion was mistaken for metastatic melanoma. To the best of authors' knowledge, this is the first case of cutaneous PEComa with melanin pigmentation. Awareness about occurrence of the lesion in the subcutaneous tissue and its unique immunoprofile would be helpful to reach correct diagnosis and to distinguish this lesion from melanoma or metastatic renal clear cell carcinoma.

Primary clear cell sarcoma of the head and neck: a case series with review of the literature

BACKGROUND

Clear cell sarcoma typically arises in deep soft tissues of the foot/ankle. Primary head and neck clear cell sarcoma is rare. We report three molecularly confirmed primary head and neck clear cell sarcoma and review the literature.

METHODS

Head and neck clear cell sarcoma with no primary elsewhere were retrieved from archival/consultation files. English language literature review of all reported head and neck clear cell sarcoma was performed.

RESULTS

Three cases were identified. The tumors, all in men, presented on the scalp of a 33-year-old, face of a 20-year-old and tongue of a 44-year-old. Tumors ranged from 0.6 to 1.4 cm. All had typical features of clear cell sarcoma, including nests of tumor cells divided by fibrous septae. One had multinucleated wreath-like giant cells. One had a focal junctional component. Immunohistochemistry was positive for S100 (three out of three), HMB45 (three out of three) and Melan-A (two out of three). All had EWSR1 rearrangements by fluorescence in situ hybridization. Follow up available for one patient revealed no evidence of disease after wide excision and radiation. Seven additional reported cases were identified and tabulated.

CONCLUSION

Head and neck clear cell sarcoma is rare but should be considered in the differential diagnosis of nested tumors with fibrous septae. Molecular analysis should be considered for definitive diagnosis regardless of location.

Cutaneous perivascular epithelioid cell tumors: A review on an infrequent neoplasm

“Perivascular epithelioid cutaneous” cell tumors (PEComa) are a family of mesenchymal tumors with shared microscopic and immunohistochemical properties: They exhibit both smooth muscle cell and melanocytic differentiation. Non-neoplastic counterpart of PEComa’s cells are unknown, as well as the relationship between extracutaneous PEComa and primary cutaneous ones. We will review the clinical setting, histopathologic features, chromosomal abnormalities, differential diagnosis and treatment options for cutaneous PEComa.

S-100 Negative Granular Cell Tumor of the Oral Cavity

Classic granular cell tumor is a mesenchymal neoplasm that commonly occurs on the skin, but is not infrequently found in the oral cavity, primarily on the dorsal tongue. Diagnosis is usually straightforward with hematoxylin and eosin stained slides. Immunohistochemical studies on classic granular cell tumor shows positive immunostaining for S-100 and vimentin, while CD68 is variably positive. We report a case of otherwise unremarkable oral granular cell tumor that was immunohistochemically negative for S-100, and positive for vimentin and CD68, and discuss the differential diagnosis. The results of the immunohistochemical studies in our case are compared with those of classic S-100 positive oral granular cell tumors, as well as cutaneous and oral S-100 negative granular cell tumors. Classic S-100 positive granular cell tumors and S-100 negative granular cell tumors of the oral cavity can only be distinguished by immunohistochemical studies; however, the necessity of this distinction is unclear, as both are benign lesions in which recurrence is unlikely.

Malignant TFE3-rearranged perivascular epithelioid cell neoplasm (PEComa) presenting as a subcutaneous mass

Perivascular epithelioid cell neoplasms (PEComas) are a group of mesenchymal tumours with concurrent melanocytic and myogenic differentiation. Although many cases are sporadic, PEComas can be associated with tuberous sclerosis. A distinct subset of deep-seated PEComas has been shown to carry TFE3 fusions. To our knowledge, this is the first reported case of primary subcutaneous malignant PEComa with molecular confirmation of TFE3 gene rearrangement.

PEComa: morphology and genetics of a complex tumor family

Perivascular epithelioid cell tumors, or PEComas, are mesenchymal neoplasms composed of histologically and immunohistochemically distinctive epithelioid or spindle cells, which are immunoreactive for both smooth muscle and melanocytic markers. The cells in PEComas are typically arranged around blood vessels and appear to form the vessel wall, often infiltrating the smooth muscle of small- to medium-sized vessels. Periluminal cells are usually epithelioid and the more peripheral cells are spindle shaped. The cells have small, round to oval nuclei, sometimes with focal nuclear atypia, and clear to eosinophilic cytoplasm, and no counterpart normal cell has been identified. The PEComa "family" now includes angiomyolipoma, pulmonary clear cell "sugar" tumor and lymphangioleiomyomatosis, primary extrapulmonary sugar tumor, clear cell myomelanocytic tumor of the falciform ligament/ligamentum teres, abdominopelvic sarcoma of perivascular epithelioid cells, and other tumors with similar features at various sites that are simply termed PEComa. Some PEComas occur in patients with tuberous sclerosis complex and share the genetic abnormalities. There is a behavioral spectrum from benign to frankly malignant, and histologic criteria have been proposed for assessing malignant potential. The differential diagnosis can include carcinomas, smooth muscle tumors, other clear cell neoplasms, and adipocytic tumors. PEComas constitute a genetically diverse group that includes neoplasms harboring TFE3 gene rearrangements and those with TSC2 mutations, indicating alternative tumorigenic pathways. Recent advances in therapy of malignant PEComas relate to increased knowledge of specific genetic changes and their effects on metabolic pathways that are susceptible to specific interventions. We review PEComas, emphasizing the diagnostic spectrum and recent immunohistochemical and genetic findings.

Immunohistochemistry in dermatopathology

CONTEXT

Immunohistochemistry is not a diagnostic test but a highly valuable tool that requires interpretation within a context.

OBJECTIVE

To review the current status and limitations of immunohistochemistry in dermatopathology.

DATA SOURCES

English-language literature published between 1980 and 2014.

CONCLUSIONS

Although immunohistochemistry is rarely completely specific or sensitive, it is an important adjunctive technique in dermatopathology and can be helpful in a series of diagnostic dilemmas.

Evaluation of the role of routine melan-A immunohistochemistry for exclusion of microinvasion in 120 cases of lentigo maligna

BACKGROUND

To assess the usefulness of routine melan-A immunohistochemistry (IHC) for exclusion of microinvasion in lentigo maligna (LM).

METHODS

One hundred and twenty cases of LM from our archives were reviewed by 2 authors with S100 protein and melan-A IHC using a red chromogen.

RESULTS

Melan-A was useful to confirm the diagnosis of LM in early lesions and to differentiate these from chronically sun-damaged skin. The presence of scattered melan-A-positive cells was noted in the dermis in 72 of 120 cases (melanophages in 36 cases, nonspecific cells different to melanophages in 16 cases, and a dual cell population in 20 cases). The significance of these cells was uncertain. Only 3 cases suspicious for microinvasion were identified: 2 on haematoxylin and eosin and 1 on S100.

CONCLUSIONS

We recommend use of melan-A to confirm the diagnosis in early lesions of LM and in the differential diagnosis from melanocytic hyperplasia in chronically sun-exposed skin. We do not recommend routine use of melan-A to identify or exclude microinvasion. However, it may have a role, in conjunction with S100, in cases with suspicious features for early invasion on haematoxylin and eosin sections.

Cutaneous PEComa: a rare entity to consider in an unusual site

PEComa is a mesenchymal neoplasm thought to derive from the perivascular epithelioid cell, a hypothetical cell type not yet identified. PEComa is a broad term that was recently expanded to include visceral, retroperitoneal, and somatic soft tissue, in addition to cutaneous tumors, which share morphological and immunohistochemical features in common with angiomyolipoma, lymphangiomyomatosis, and clear cell "sugar" tumor. The latter have distinct, site-related, clinical, morphological, and biological features. PEComas share features of concurrent melanocytic and myocytic differentiation. Most cases are sporadic, but renal and pulmonary PEComas can be part of the tuberous sclerosis syndrome more often than PEComas from other sites. We report a case of cutaneous PEComa to raise awareness of the entity occurring at this site and caution against misinterpretation as a primary or metastatic malignancy, for example melanoma or renal cell carcinoma, clear cell type.

Primary cutaneous perivascular epithelioid cell tumor: a clinicopathological and molecular reappraisal

BACKGROUND

Perivascular epithelioid cell tumor (PEComa) is a rare neoplasm of uncertain histogenesis with a mixed myomelanocytic immunophenotype, rarely arising in the skin (primary cutaneous PEComa [pcPEComa]).

OBJECTIVE

We analyzed the clinicopathological features of 8 pcPEComas, assayed for DNA copy number changes and for initiating mutations common in melanocytic neoplasms.

METHODS

pcPEComas were evaluated using immunohistochemistry, comparative genomic hybridization, and DNA sequencing.

RESULTS

pcPEComas were erythematous nodules, mostly in the lower extremities of women (5/8), composed of large pale-staining epithelioid cells. The patient's age range was 26 to 67 (mean 46) years. The percentages of tumors staining positively were as follows: micro-ophthalmia-associated transcription factor, NKI/C3, bcl-1, E-cadherin, and cathepsin K (100%); HMB-45, 4E-binding protein 1, and CD68 (88%); smooth muscle actin and muscle-specific actin (40%); S100 (38%); calponin (20%); desmin (13%); and melan-A, SOX10, and keratin (0%). No chromosomal copy number changes or initiating mutations were identified.

LIMITATIONS

Small sample size is a limitation.

CONCLUSIONS

pcPEComas have a different molecular signature than extracutaneous tumors and are unrelated to tuberous sclerosis. However, the common expression of 4E-binding protein 1 points to a role of the mTOR pathway in their pathogenesis. Because pcPEComas are diagnostically challenging, we propose that micro-ophthalmia-associated transcription factor, NKIC3, smooth muscle actin, desmin, bcl-1, cathepsin K, and 4E-binding protein 1 can be used when evaluating a possible pcPEComa.

PEComa of the nasal cavity with worrisome histologic features and benign behavior: a case report

OBJECTIVES

PEComas (perivascular epithelioid cell tumors) are a family of neoplastic lesions that share overlapping ultrastructure and morphological and immunohistochemical appearance and include angiomyolipoma, lymphangioleiomyomatosis, and clear cell "sugar" tumor of the lung, as well as similar tumors that occur in a variety of visceral, cutaneous, and soft tissue sites throughout the body.

METHODS

A 40-year-old woman came to medical attention because of epistaxis and because of unilateral nasal obstruction of 3 months' duration. Endoscopic examination revealed a well-demarcated exophytic lesion attached to the anterior portion of the middle turbinate.

RESULTS

The lesion was superficially located, and therefore amenable to complete surgical excision. Seven years after surgery, the patient is alive and well, without evidence of local recurrence or metastastic disease. Based on morphological and immunohistochemical appearance, a diagnosis of PEComa with worrisome histologic features was rendered.

CONCLUSIONS

In the present study, we describe a PEComa that occurred in the nasal cavity and discuss the behavior of this entity. The importance of recognizing this disease will ensure its consideration in the differential diagnosis of tumors of the head that have similar morphological features. The histogenesis of PEComa still remains elusive, and collection of additional cases with a prolonged follow-up will be important in accurately determining the behavior of these distinctive tumors.

Recently characterized soft tissue tumors that bring biologic insight

Previously unrecognized but clinicopathologically (and often molecularly) distinct types of soft tissue tumor continue to be characterized, allowing wider recognition, more consistent application of diagnostic criteria, more reliable prediction of tumor behavior and enhancement of existing classification schemes. Examples of such 'entities' that have become much better understood over the past decade or so include deep 'benign' fibrous histiocytoma, hemosiderotic fibrolipomatous tumor, PEComa, spindle cell liposarcoma, myoepithelial tumors of soft tissue and spindle cell/sclerosing rhabdomyosarcoma. These tumor types, as well as the insights which they have engendered, are briefly reviewed here.

PEComa of the gastrointestinal tract: clinicopathologic study of 35 cases with evaluation of prognostic parameters

Perivascular epithelioid cell tumors (PEComas) are distinctive mesenchymal neoplasms that most often arise in the retroperitoneum, visceral organs, and abdominopelvic sites and usually show reactivity for melanocytic and smooth muscle markers. Fewer than 20 PEComas of the gastrointestinal (GI) tract have been reported, and behavior and criteria for malignancy are incompletely defined. The purpose of this study was to examine the clinicopathologic features of a series of GI PEComas and to evaluate prognostic parameters. A total of 35 PEComas of the GI tract were retrieved from consult and surgical files. Clinical and pathologic features were evaluated, and immunohistochemical analysis was performed. Clinical follow-up information was obtained from medical records and referring physicians. Nineteen patients were female and 16 male (median age 45 y; range, 7 to 70 y). One patient had tuberous sclerosis. Nineteen tumors arose in the colon, 12 in the small bowel, 2 in the stomach, and 1 each in gallbladder and omentum. Median tumor size was 6.2 cm (range, 0.8 to 22 cm). Three tumors were limited to the mucosa and submucosa, 8 extended to the muscularis propria, 15 to the subserosa/serosa, and 8 into the mesentery. The tumors were composed of nests and sheets of usually epithelioid cells with abundant granular eosinophilic to clear cytoplasm, surrounded by a delicate capillary vasculature. Thirteen tumors had mixed epithelioid and spindle cell components, and 2 were purely spindled. Sixteen tumors showed marked nuclear atypia. Seventeen tumors contained occasional pleomorphic cells, and 12 showed diffuse cellular pleomorphism. The median mitotic rate was 2/10 HPF (range, 0 to 36). Vascular invasion was present in 5 cases, and 16 tumors showed necrosis. By immunohistochemistry, 23/35 were positive for HMB45, 23/34 for melan-A, 15/25 for MiTF, 20/35 for smooth muscle actin, 26/35 for desmin, and 3/20 for TFE3. Focal cytoplasmic S100 protein was present in 5/27 cases, 2/25 cases were positive for KIT, and 1 case each was positive for EMA and keratin. Follow-up information was available for 31 patients (median 36 mo; range, 2 to 176 mo). Thirteen patients have developed metastases (10 liver, 3 peritoneum, 4 lymph node, 3 lung, 1 bone, 1 brain, and 1 adrenal). Thus far, 5 patients have died of disease. Metastases were significantly associated with marked atypia, diffuse pleomorphism, and mitoses ≥2/10 HPF. In summary, PEComas of the GI tract occur at similar frequency in female and male patients, most commonly involve the colon, and exhibit variable clinical behavior, ranging from benign lesions to aggressive, high-grade sarcomas. The presence of marked nuclear atypia, diffuse pleomorphism, and mitotic activity are the strongest predictors of malignant behavior.

Eruptive dermal clear cell desmo-plastic mesenchymal tumors with perivascular myoid differentiation in a young boy. A clinical, histopathologic, immunohistochemical and electron microscopy study of 17 lesions

Clear cell tumors of the skin are observed in a wide variety of benign and malignant conditions with different histogenesis, sharing the presence of cells with abundant clear cytoplasm. Herein, we report the clinicopathologic features of a healthy young patient affected by asymptomatic, eruptive and disseminated, benign clear cell dermal tumors since early infancy. Neither family history nor genetic testing and counseling provided further useful information. The lesions were mostly confined to the face and lower left extremity with pink teleangiectatic papules and small nodules. Over a 4-year period, a total of 16 different cutaneous lesions were biopsied and histopathologic and immunohistochemical studies carried out; an additional lesion was also removed for electron microscopy examination. Histopathology evidenced multiple perivascular growths of spindle to oval and round cells intermingled with clear/granular cells throughout the dermis, with prominent desmoplasia and numerous capillary-like vessels with focal hemangiopericytoma-like features. Immunohistochemical neoplastic cells were uniformly positive for h-caldesmon and focally smooth muscle α-actin and CD13 indicating myoid differentiation whereas the consistent diffuse cytoplasmic staining for lysosome antigen, such as CD68PG-M1 and NKI/C3 along with the ultrastructural findings supported the view of a lysosome-mediated apoptotic process. The differential diagnosis with other clear cell cutaneous neoplasms is discussed.

Mesenchymal Tumors of the Gastrointestinal Tract Other than GIST

Mesenchymal tumors involve the gastrointestinal (GI) tract more frequently than other visceral organs. Many such tumors are small, and are benign and increasingly being detected incidentally during colonoscopic screening. Some tumors show distinctive features at this site, such as schwannoma and clear cell sarcoma-like tumor of the GI tract. Without knowledge of these features, recognition of these tumor types can be difficult. This reviews addresses recent developments and diagnostic features of mesenchymal tumors of the GI tract other than gastrointestinal stromal tumor (GIST).

Cutaneous PEComa does not harbour TFE3 gene fusions: immunohistochemical and molecular study of 17 cases

AIMS

The family of perivascular epithelioid cell tumours (PEComas) comprises a related group of mesenchymal tumours of uncertain origin that show both smooth muscle and melanocytic differentiation markers. TFE3 nuclear immunoreactivity may be viewed as a supporting marker, as it has been found in a subset of visceral PEComas. We immunohistochemically analysed 17 cases of primary cutaneous PEComas for TFE3, and five of them also for SOX-10, and also analysed them by FISH for TFE3 rearrangement.

METHODS AND RESULTS

PEComas presented as skin-coloured tumours, in 12 women and five men, with a median age of 49.5 years. Tumours showed either a mixed clear cell-epithelioid cell pattern or a monomorphous clear cell pattern. None of the primary cutaneous PEComas showed detectable TFE3 or SOX-10 positivity. FISH assay for TFE3 rearrangement yielded negative results in all of the tested tumours.

CONCLUSIONS

Cutaneous PEComas are mostly composed of clear cells, and, unlike a subset of visceral and deep-seated PEComas, cutaneous PEComas consistently lack TFE3 expression. Owing to the lack of SOX-10 expression, a neural crest origin could not be shown.

[A case of primary cutaneous PEComa]

BACKGROUND

PEComas (PEC: Perivascular epithelioid cell) are tumours expressing both melanocytic and myogenic markers. The clinical features are non-specific.

PATIENTS AND METHODS

A 55-year-old woman presented with a non-specific tumour on her right arm. Histological examination revealed an intradermal tumour composed of clear epithelial cells. The tumour was positive for HMB45 and protein S100, and was negative for Melan-A and actin. A diagnosis of PEComa was retained despite negative myogenic markers.

DISCUSSION

PEComas are neoplasms composed of nests and fascicles of clear to granular epithelioid cells that express both melanocytic markers (HMB45, Melan-A, NK1C3, tyrosinase) and myogenic markers (actin, caldesmin, desmin, calponin), whereas S100 protein and cytokeratins are usually absent. Included in this broad category are angiomyolipoma, clear-cell "sugar" tumours and lymphangioleiomyoma. Some deep PEComas may have a malignant course. Cutaneous primitive forms are exceptional and often benign. Histological differential diagnoses to consider are those of clear-cell tumours: paraganglioma-like dermal melanocytic tumour, melanoma, metastatic clear-cell renal carcinoma and epithelioid sarcoma. In our patient, a diagnosis of cutaneous primitive PEComa was retained despite the absence of myogenic markers and the positivity of the protein S100, based on the cytological and immunohistochemical features, which were not evocative of any other diagnosis.

CONCLUSION

Cutaneous PEComa are non-specific tumours. Histological analysis confirms the diagnosis and allows other more aggressive tumours to be ruled out.

Unusual myoid, perivascular, and postradiation lesions, with emphasis on atypical vascular lesion, postradiation cutaneous angiosarcoma, myoepithelial tumors, myopericytoma, and perivascular epithelioid cell tumor

In recent years, a number of new soft tissue tumor entities have been described that occur in the skin only, or that also occur in other sites but form clinically and pathologically distinct subsets when arising in the skin and subcutaneous tissue. These include a variety of mesenchymal lineages and have variable malignant potential, although superficial malignant soft tissue tumors generally have a more favorable outcome than their more deeply located counterparts. This article reviews the clinical and pathologic features and differential diagnoses of atypical vascular lesion, postradiation cutaneous angiosarcoma, myoepithelioma, myopericytoma, and perivascular epithelioid cell tumor.

Update on immunohistochemistry in melanocytic lesions

This article is an up-to-date overview of the potential uses and limitations of immunohistochemistry (IHC) in melanocytic lesions. The information is intended to assist dermatopathologists and dermatologists who read slides to appropriately use IHC in this setting. In addition, dermatologists who do not review microscopic slides will better understand the rationale of the pathologist when reading and interpreting the pathology report.

Clear Cell Tumors of Soft Tissue

Clear cell lesions of soft tissue include varying morphologic patterns and a range of clinical behaviors and prognoses. Benign lesions include perivascular epithelioid cell tumors, clear cell fibrous papule, and distinctive dermal clear cell mesenchymal tumor; malignant tumors include clear cell sarcoma, liposarcoma, and rare malignant perivascular epithelioid cell tumors. Clear cell variants of other benign and malignant soft tissue tumors include fibrous histiocytoma, atypical fibroxanthoma, myoepithelioma, leiomyoma and leiomyosarcoma, and rhabdomyosarcoma. Metastatic clear cell tumors, including renal cell carcinoma and adrenal cortical carcinoma, should be considered in the differential diagnosis and excluded through clinical history, imaging studies, and immunohistochemical stains.

Malignant glomus tumor of the palm: a case report

The author herein reports on a glomus tumor of the palm. A 71-year-old man consulted our hospital because of a tumor on the left palm. The tumor was deeply seated, and MRI and CT showed a deep cystic tumor adjacent to the bone. An excision of the tumor was therefore performed. Grossly, the tumor was red and partly cystic. The tumor was well defined from the surrounding tissues, and measured 25 × 24 × 22 mm. Microscopically, the tumor consisted of epithelioid perivascular cells (glomus cells) located around the blood vessels. Cystic changes and hyalinization areas were scattered. The tumor cells had moderately hyperchromatic nuclei. Nuclear pleomorphism was noticed, nucleoli were absent and apparent mitotic figures were not recognized. There were no areas of necrosis. Immunohistochemically, the glomus cells were positive for vimentin and α-smooth muscle actin. They were negative for cytokeratins, epithelial membrane antigen, CD34, CD31, factor VIII-related antigen, S100 protein, p53 protein, desmin and melanosome. The Ki-67 labeling was 5%. The tumor was diagnosed as a malignant glomus tumor because of its deep location and size > 2 cm , according to the criteria of one group. The tumor recurred 12 months later, and a further excision was performed. No metastases were found. Now, the patient is being strictly followed up.

Non-melanocytic mimics of melanocytic neoplasms

On histopathologic examination, many non-neoplastic conditions mimic benign or malignant neoplasms. Alternatively, some benign and malignant neoplasms can also mimic non-neoplastic lesions. This is true of all organ systemsskin is no exception. Examples of these mimickers can be found in skin lesions of almost all tissue types, including those that are melanocytic, lymphoid, epithelial, neural, vascular, neuroendocrine, and fibrohistiocytic. Melanocytic neoplasms are particularly important as it's challenging to differentiate them as being benign or malignant, and it's difficult to tell them apart from non-melanocytic neoplasms. This review illustrates examples of non-melanocytic lesions that disguise themselves as melanocytic.