Hemangioendothelioma

Hemangioendothelioma is the term used to name those vascular neoplasms that show a borderline biological behavior, intermediate between entirely benign hemangiomas and highly malignant angiosarcomas. Although originally spindle cell hemangioendothelioma was proposed as a specific clinicopathologic variant of hemangioendothelioma, currently, it is considered as an entirely benign lesion, and thus, the name spindle cell hemangioma seems to be the most accurate for this lesion. Authentic hemangioendotheliomas involving the skin and soft tissues include papillary intralymphatic angioendothelioma (also known as Dabska tumor), retiform hemangioendothelioma, kaposiform hemangioendothelioma, epithelioid hemangioendothelioma, pseudomyogenic hemangioendothelioma (also known as epithelioid sarcoma-like hemangioendothelioma), and composite hemangioendothelioma. Each of these neoplasms exhibit characteristic histopathologic features. The most characteristic finding of papillary intralymphatic hemangioendothelioma consists of papillary tufts, with a central hyaline core lined by hobnail-like endothelial cells protruding into the lumina. Retiform hemangioendothelioma is an infiltrative neoplasm composed of elongated arborizing vessels, arranged in an anastomosing pattern that resembles that of the rete testis, and lined by a single layer of hobnail-like endothelial cells that protrude within the narrow lumina. Kaposiform hemangioendothelioma is composed of several solid poorly circumscribed nodules, and each nodule is composed of a mixture of small capillaries and solid lobules of endothelial cells arranged in a glomeruloid pattern. A frequent finding consists of the presence of areas of lymphangiomatosis adjacent to the solid nodules. Epithelioid hemangioendothelioma is composed of cords, strands, and solid aggregates of round, oval, and polygonal cells, with abundant pale eosinophilic cytoplasm, vesicular nuclei, and inconspicuous nucleoli, embedded in a fibromyxoid or sclerotic stroma. Many neoplastic cells exhibit prominent cytoplasmic vacuolization as an expression of primitive vascular differentiation. Pseudomyogenic hemangioendothelioma is a poorly circumscribed, fascicular lesion with infiltrative borders composed of round or oval neoplastic cells, with vesicular nuclei and inconspicuous nucleoli, and ample homogeneous eosinophilic cytoplasm, giving them a rhabdomyoblastic appearance. Finally, composite hemangioendothelioma is the term used to name locally aggressive vascular neoplasms of low-grade malignancy showing varying combinations of benign, low-grade malignant, and high-grade malignant vascular components. From the immunohistochemical point of view, proliferating cells of all hemangioendotheliomas express a lymphatic endothelial cell immunophenotype. Most hemangioendotheliomas are low-grade vascular neoplasms, with a tendency to recur locally and a low metastatic potential, mostly to regional lymph nodes. Epithelioid hemangioendothelioma, especially large lesions and those located in deep soft tissues, seems to have a more aggressive biological behavior.

Histopathologic patterns associated with external agents

A large number of foreign substances may penetrate the skin for both voluntary and involuntary reasons. The voluntary group includes the particulate materials used in tattoos and cosmetic fillers, whereas the involuntary group is almost always caused by accidental inclusion of external substances secondary to cutaneous trauma. This article focuses on the histopathologic findings seen in cutaneous reactions to exogenous agents, with special emphasis on the microscopic morphology of the external particles in recognizing specifically the involved substance (something that is becoming increasingly important in the event of litigation).

Giant benign lymphangioendothelioma

Benign lymphangioendothelioma is a rare locally infiltrative vascular neoplasm, presenting as a slow-growing, asymptomatic, reddish-violaceous plaque. Histopathologically, it is characterized by irregular and thin-walled vascular spaces, lined by a single and discontinuous layer of flat endothelial cells, dissecting dermal collagen bundles. We present the case of a 75-year-old man with a giant benign lymphangioendothelioma, to our knowledge, the largest example described in the literature. The immunohistochemical expression of Wilms tumor 1 gene is useful in vascular lesions to differentiate malformations from proliferative endothelial lesions. In our case, the positivity for WT1 supports the neoplastic nature of this lesion.

A distinct subset of atypical Spitz tumors is characterized by BRAF mutation and loss of BAP1 expression

We recently reported that germline mutations in BAP1 cause a familial tumor syndrome characterized by high penetrance for melanocytic tumors with distinct clinical and histologic features. Melanocytic neoplasms in affected individuals harbored BRAF mutations, showed loss of BAP1 expression, and histologically resembled so-called "atypical Spitz tumors" (ASTs). ASTs are an ill-defined and probably heterogenous group of melanocytic tumors that display histologic features seen in both Spitz nevi and melanomas. Their biological behavior cannot be reliably predicted. In view of the histologic similarities of the familial tumors and ASTs, we hypothesized that a subset of ASTs might harbor genetic alterations seen in the familial tumors. To address this hypothesis, we analyzed 32 sporadic ASTs for BRAF mutations and for BAP1 expression. Nine (28%) sporadic ASTs showed loss of BAP1 expression, of which 8 (89%) had concomitant BRAF mutations. Only 1 of the BAP1-positive ASTs (4%) had a BRAF mutation (P<0.0001). BRAF-mutated, BAP1-negative tumors were primarily located in the dermis and were composed entirely or predominantly of epithelioid melanocytes with abundant amphophilic cytoplasm and well-defined cytoplasmic borders. Nuclei were commonly vesicular and exhibited substantial pleomorphism and conspicuous nucleoli. The combination of BRAF mutation and loss of nuclear BAP1 expression thus characterizes a subset of ASTs with distinct histologic features. The typical morphology of these tumors and BAP1 immunohistochemistry provide pathologic clues that will enable accurate identification of this subset. Future studies are necessary to determine whether this subset has a predictable clinical behavior.

Histological and genetic evidence for a variant of superficial spreading melanoma composed predominantly of large nests

Cutaneous melanomas are characterized by a range of histological appearances, and several morphological variants have been described. In this study, we report a variant of superficial spreading melanoma that is characterized by large, irregular junctional melanocytic nests. The junctional nests varied in shape and size, showed focal tendency to confluence, and were often surrounded by a cuff of epidermal keratinocytes. The melanocytes comprising the nests showed variable cytological atypia. In most of the cases, scant intraepidermal or junctional single melanocytes were seen, and other well-documented diagnostic criteria for melanoma were lacking, and as a result, histological recognition of these tumors as melanoma was difficult. Some cases were associated with an invasive dermal component or showed evidence of sun damage. To provide supporting evidence for malignancy, we analyzed these tumors for genomic aberrations. Using array comparative genomic hybridization (aCGH), we identified multiple genomic aberrations in all analyzed cases. A similar pattern of genomic aberrations was seen in a control group of bona fide superficial spreading melanomas, suggesting that these 'melanomas composed exclusively or predominantly of large nests' are indeed variants of superficial spreading melanoma. Fluorescence in-situ hybridization (FISH) was positive in 40% of the cases. However, using aCGH, the FISH-negative cases showed multiple genomic aberrations in regions that are not covered by FISH. The low sensitivity of the FISH test can be explained by the fact that FISH only evaluates four genomic loci for aberrations, whereas aCGH surveys the entire genome. In summary, we present histological and molecular genetic evidence for a morphological variant of superficial spreading melanoma. Awareness of the histological features will aid in their correct diagnosis as melanoma, and in difficult cases, judicious application of ancillary tests such as aCGH (rather than FISH) will assist accurate diagnosis.

Abstract 3671: A distinct subset of atypical Spitz tumors is characterized by BRAF mutation and loss of BAP1 expression

We recently reported that germline mutations in BAP1 cause a familial tumor syndrome characterized by high penetrance for melanocytic tumors with distinctive clinical and histologic features. Melanocytic neoplasms in affected individuals harbored BRAF mutations, showed loss of BAP1 expression, and histologically resembled so-called “atypical Spitz tumors” (ASTs). ASTs are an ill-defined and probably heterogenous group of melanocytic tumors that display histologic features seen in both Spitz nevi and melanomas. Their biologic behavior cannot be reliably predicted. Based on the histologic similarities of the familial tumors and ASTs, we hypothesized that a subset of ASTs might harbor genetic alterations seen in the familial tumors. To address this hypothesis, we analyzed 32 sporadic ASTs for BRAF mutations, and for BAP1 expression. To determine the utility of immunohistochemistry to assess BAP1 status, we analyzed samples from 42 patients with the above syndrome as well as 46 melanocytic nevi and found that loss of BAP1 expression was restricted to patients with the syndrome. Nine (28%) sporadic ASTs showed loss of BAP1 expression, of which of 8 (89%) had concomitant BRAF mutations. Only one of the BAP1-positive ASTs (4%) had a BRAF mutation (p&lt;0.0001). BRAF mutated, BAP1-negative tumors were primarily located in the dermis, and were composed entirely or predominantly of epithelioid melanocytes with abundant amphophilic cytoplasm and well-defined cytoplasmic borders. Nuclei were commonly vesicular, and exhibited substantial pleomorphism and conspicuous nucleoli. The combination of BRAF mutation and loss of nuclear BAP1 expression thus characterizes a subset of ASTs with distinctive histologic features. The typical morphology of these tumors and BAP1 immunohistochemistry provide pathologic clues that will enable accurate identification of this subset. Future studies are necessary to determine whether this subset has a predictable clinical behavior.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3671. doi:1538-7445.AM2012-3671

Rare human skin infection with Corynebacterium ulcerans: transmission by a domestic cat

Corynebacterium ulcerans is mainly known for its ability to cause animal infections. Some strains of C. ulcerans produce diphtheria toxin, which can cause life-threatening cardiopathies and neuropathies in humans. Human cutaneous C. ulcerans infection is a very rare disease that mimics classical cutaneous diphtheria. We present a very rare case of a C. ulcerans skin infection caused by a non-diphtheria toxin-producing strain of C. ulcerans that resolved after 3 weeks of therapy with amoxicillin-clavulanate. A pet cat was the probable source of infection. The presence of C. ulcerans in the mouth of the cat was confirmed by 16S rRNA gene analysis and the API Coryne system. In cases of human infection with potentially toxigenic corynebacteria, it is important to determine the species and examine the isolate for diphtheria toxin production. If toxigenicity is present, diphtheria antitoxin should be administered immediately. Carriers and potential infectious sources of C. ulcerans include not only domestic livestock but also pet animals. For the primary prevention of disease caused by diphtheria toxin-producing corynebacteria, vaccination with diphtheria toxoid is recommended.

Postradiation cutaneous angiosarcoma after treatment of breast carcinoma is characterized by MYC amplification in contrast to atypical vascular lesions after radiotherapy and control cases: clinicopathological, immunohistochemical and molecular analysis of 66 cases

Postradiation cutaneous vascular lesions after treatment of breast carcinoma comprise a heterogeneous group of benign, atypical, and malignant lesions and are best regarded as points along a morphological spectrum. We analyzed a series of cutaneous angiosarcomas after treatment of breast cancer in comparison with control cases and cases of atypical vascular lesions with special emphasis on the expression and amplification of MYC. The 66 cases were divided into control cases (5), cases in which a slight vascular proliferation was seen after radiotherapy of breast cancer (12), cases of atypical vascular lesions after radiotherapy (16), cases of postradiation cutaneous angiosarcomas (25), and cases of angiosarcomas of skin and soft tissues unrelated to radiotherapy (8). None of the control cases (2 M, 3 F, 20-76 years), of cases showing slight vascular proliferation, dermal fibrosis and inflammation after radiotherapy of breast cancer (12 F, 48-79 years), of cases of atypical vascular lesions after radiotherapy (16 F, 29-81 years), and of cases of angiosarcomas of skin and soft tissues unrelated to radiotherapy (3 M, 5 F, 25-92 years) showed an amplification of MYC by FISH analysis. In striking contrast, in all cases of postradiation cutaneous angiosarcomas (25 F, 46-95 years), MYC amplification was found by FISH analysis in a variable number of counted nuclei. Immunohistochemically, strong positive nuclear staining for MYC and prox-1 was seen in cases of postradiation cutaneous angiosarcoma, whereas control cases and cases of atypical vascular proliferation after radiotherapy were negative for MYC, and stained only focally positive for prox-1 in a number of cases. In conclusion, the presence of MYC amplification represents an important additional diagnostic tool in the distinction of postradiation cutaneous angiosarcomas from atypical vascular lesions after radiotherapy. Immunohistochemical stainings for MYC are useful for mapping of these lesions and for careful tumor margin control.

Fibroepithelioma of Pinkus is a true basal cell carcinoma developing in association with a newly identified tumour-specific type of epidermal hyperplasia

BACKGROUND

Fibroepithelioma of Pinkus (FEP) has long been viewed as a subtype of basal cell carcinoma (BCC). Recently, however, the proposal has been made that FEP represents a fenestrated trichoblastoma/trichoepithelioma. One of the main arguments is the presence of Merkel cells in FEP, which typically do not occur in BCC.

OBJECTIVES

As the new stem cell marker, PHLDA1 (TDAG51), labels trichoepithelioma but not BCC, our aim was to characterize its staining pattern in FEP. Because adnexal tumours have been viewed as recapitulating embryogenesis, we also examined PHLDA1 immunoreactivity in the skin of human embryos and fetuses.

METHODS

We studied immunohistochemically PHLDA1 staining in 31 FEPs, 14 BCCs and 16 trichoepitheliomas and compared this with its staining pattern in embryonic skin and with the distribution of Merkel cells.

RESULTS

In FEP, PHLDA1 labels the anastomosing network of thin cellular strands but not the basaloid nubbins. During embryogenesis, PHLDA1 stains the basal cell layer of the epidermis, as long as adnexal structures develop. Immunoreactivity for PHLDA1 correlates positively with the presence of Merkel cells.

CONCLUSIONS

We propose that the thin anastomosing network of PHLDA1-positive cells represents a type of epidermal hyperplasia specific to FEP. The multifocal BCCs that are PHLDA1-negative develop from this network which becomes incorporated into the tumour. Viewing the anastomosing network as a tumour-specific form of epidermal hyperplasia explains the hitherto enigmatic presence of Merkel cells in FEP.

EWSR1 gene rearrangement occurs in a subset of cutaneous myoepithelial tumors: a study of 18 cases

Cutaneous myoepithelial tumors form a clinicopathological spectrum ranging from mixed tumor to myoepithelioma and myoepithelial carcinoma. Recently, EWSR1 rearrangement has been described in a subset of soft tissue myoepithelial tumors, whereas the cutaneous counterparts showed this aberration in a minority of cases. This raises the question whether cutaneous myoepithelial tumors have comparable genetic alterations. We examined 18 cases of cutaneous myoepithelial tumors arising in 7 female and 11 male patients (age range, 34-86 years; mean, 58 years). Eight mixed tumors occurred at the head, and one at the scrotum. Six myoepitheliomas arose at the extremities, and one case each at the back and head. One myoepithelial carcinoma occurred at the cheek. The tumor size ranged from 0.3 to 1.7 cm (mean, 1.0 cm). All mixed tumors and three myoepitheliomas were limited to the dermis. Four myoepitheliomas and the myoepithelial carcinoma involved the subcutis. Mixed tumors and myoepitheliomas were composed of myoepithelial cells with a variable cytomorphology, architecture and stromal background. Ductal structures were seen by definition in mixed tumors. The myoepithelial carcinoma represented an infiltrative dermal neoplasm consisting of atypical spindle cells. Immunohistochemically, all cases tested were positive for EMA and calponin, whereas S100, CK, ASMA and GFAP were expressed in 90%, 80%, 78% and 50% of the cases tested, respectively. By fluorescent in situ hybridization analysis, 7 out of 16 cases (44%) exhibited EWSR1 rearrangement. Four of them were mixed tumors, two were myoepitheliomas and one was a myoepithelial carcinoma, confirming that these lesions represent a spectrum of dermal myoepithelial tumors. Follow-up information, available for five patients (including the patient with a myoepithelial carcinoma), revealed no evidence of disease in all cases (range, 6-72 months). Our study provides a genetic relationship of myoepithelial tumors of the skin with their counterparts in soft tissue, bone and visceral localization by sharing EWSR1 rearrangement.