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Lymphatic malformation (LM) is a vascular anomaly from lymphatic endothelial cells (ECs), and a fraction of the patients could progress to the deadly malignant lymphangiosarcoma (LAS). Using genetic tools to delete an essential autophagy gene Rb1cc1/FIP200 or its mutation specifically blocking its autophagy function, we demonstrated that autophagy inhibition abrogated LM progression to LAS although not affecting LM formation in our recently developed mouse model of LAS. Analysis of the mouse models in vivo and vascular tumor cells in vitro showed that autophagy inhibition reduced vascular tumor cell proliferation in vitro and tumorigenicity in vivo without affecting mTORC1 signaling as an oncogenic driver directly. Transcriptional profiling of autophagy-deficient tumor cells and further mechanistic studies revealed a role for osteopontin (OPN) and its downstream Jak/Stat3 signaling in mediating regulation of vascular tumor cells by autophagy. Together, these results support potential new prophylactic strategies to targeting autophagy and/or its downstream OPN expression to prevent progression of the benign LM to the malignant and deadly LAS. Abbreviations: LM: lymphatic malformation; EC: endothelial cell; LAS: lymphangiosarcoma; OPN: osteopontin; RB1CC1: RB1 Inducible Coiled-Coil 1; FIP200: FAK family-interacting protein of 200 kDa.

Competing Interests: Disclosure The authors report no conflicts of interest in this work.

Background: Composite haemangioendothelioma is a rare vascular neoplasm with indolent to intermediate malignant potential. Diagnosis of this disease relays on histopathological identification of at least two different morphologically distinctive vascular components in proper clinical settings. Exceedingly rare cases of this neoplasm can exhibit areas resembling high-grade angiosarcoma, which does not change the biological behaviour. Such lesions tend to occur in the setting of chronic lymphoedema and thus, can mimic Stewart-Treves syndrome, which has a much worse clinical outcome and prognosis., Case Presentation: We present a case of 49 years old male suffering from chronic lymphoedema of the left lower extremity who had developed a composite haemangioendothelioma with high grade angiosarcoma-like areas mimicking the Stewart-Treves syndrome. Given the multifocality of the disease, the only potentially curable surgical treatment would be hemipelvectomy, which was refused by the patient. The patient has been followed-up, with no signs of local progression of the remaining disease, nor a distant spread outside the involved extremity for two years., Conclusions: Composite haemangioendothelioma represents a rare malignant vascular tumour, with significantly more favourable biological behaviour than angiosarcoma, even in cases where angiosarcoma-like areas are present. For that reason, composite haemangioendothelioma can be easily misdiagnosed as true angiosarcoma. The rarity of this disease unfortunately hampers the development of clinical practice guidelines and the implementation of treatment recommendations. Most of the patients with localized tumour are treated by wide surgical resection, without neo- or adjuvant radiotherapy or chemotherapy. However, in the case of this diagnosis, the watch-and-wait approach is better than mutilating procedure, highlighting the necessity of establishing of the correct diagnosis., (© 2023. The Author(s).)

Backgound: The mechanistic target of rapamycin complex 1 (mTORC1) is important in the development and progression of many cancers. Targeted cancer therapy using mTORC1 inhibitors is used for treatment of cancers; however, their clinical efficacies are still limited., Methods: We recently created a new mouse model for human lymphangiosarcoma by deleting Tsc1 in endothelial cells and consequent hyper-activation of mTORC1. Using Tsc1 iΔEC tumour cells from this mouse model, we assessed the efficacies of histone deacetylase (HDAC) inhibitors as anti-tumour agents for mTORC1-driven tumours., Results: Unlike the cytostatic effect of mTORC1 inhibitors, HDAC inhibitors induced Tsc1 iΔEC tumour cell death in vitro and their growth in vivo. Analysis of several HDAC inhibitors suggested stronger anti-tumour activity of class I HDAC inhibitor than class IIa or class IIb inhibitors, but these or pan HDAC inhibitor SAHA did not affect mTORC1 activation in these cells. Moreover, HDAC inhibitor-induced cell death required elevated autophagy, but was not affected by disrupting caspase-dependent apoptosis pathways. We also observed increased reactive oxygen species and endoplasmic reticulum stress in SAHA-treated tumour cells, suggesting their contribution to autophagic cell death, which were dependent on mTORC1 hyper-activation., Conclusion: These studies suggest a potential new treatment strategy for mTORC1-driven cancers like lymphangiosarcoma through an alternative mechanism.

An 11-y-old spayed female German Shepherd was presented for a second opinion of ventral cervical swelling of 3-mo duration. On examination, the dog had significant dependent ventral cervical swelling. Enlarged lymph nodes with cystic changes and severe edematous facial swelling were noted on computed tomography. Fine-needle aspiration of the ventral cervical swelling revealed yellow-tinged fluid, with a predominance of lymphoid cells noted on cytologic examination. On cervical exploratory surgery, the left mandibular lymph node was surrounded by a large fluid pocket; biopsies of the lymph node were obtained. Impression smear cytology, flow cytometry, PCR for antigen receptor gene rearrangements, and histopathology were performed on samples from the left mandibular lymph node. Impression smear cytology revealed a population of atypical discrete cells. Flow cytometry identified a population of CD34+/CD45- large cells. A tumor of endothelial origin within the medulla of the lymph node was identified by histopathology, and lymphangiosarcoma was confirmed based on prospero-related homeobox gene 1 ( PROX1 ) immunoreactivity. Our study describes the challenges in the diagnosis of a rarely reported entity and highlights that neoplastic endothelial cells should be considered as a differential when high proportions of CD34+/CD45- cells are present in flow cytometry.

We report 21 cases of a distinctive and unique vascular tumor which we propose to be a pure lymphatic-type angiosarcoma characterized by architectural and growth characteristics of angiosarcoma, cytologic, and immunohistochemical features of lymphatic differentiation, a prominent lymphocytic infiltrate, and variable nuclear grade. Patients included 12 males and 9 females with a median age of 65 years (range: 32 to 95 y). Tumors involved the head and neck (n=11), lower extremities (n=5), trunk (n=4), and upper extremity (n=1) and were located superficially in the dermis and/or subcutis. Tumors were designated "low grade" (n=10) when the nuclear grade was low, and vascular channel formation was evident throughout but with multilayering of endothelium within the vessels. Cases were designated "high grade" (n=11) when nuclei appeared higher grade with more rounded contours and prominent nucleoli and when solid areas predominated over vascular channel formation. A striking feature of both groups was the presence of a dense, lymphocytic infiltrate with occasional germinal center formation. All cases strongly and diffusely expressed at least 1 lymphatic marker (21/21) with podoplanin (17/19) and Prox-1 (11/11) more commonly expressed than LYVE-1 (5/10). No consistent molecular alteration was identified. Follow-up on 17 patients (median: 41 mo, mean: 54 mo) showed 10 patients were alive without disease, 5 were alive with disease, 1 died of other cause, and 1 died of disease. Local recurrence developed in 9 cases and metastasis in 2 cases, although neither correlated with grade as defined. On the basis of clinical follow-up to date, the natural history of lymphatic-type angiosarcoma appears to be more favorable than other forms of cutaneous angiosarcoma.

Kaposi sarcoma is a vascular sarcoma with 4 clinical variants: classic Kaposi sarcoma, which mainly affect the extremities of elderly patients and follows a chronic, generally indolent course; African Kaposi sarcoma; immunosuppression-associated Kaposi sarcoma; and AIDS-associated Kaposi sarcoma. Type8 human herpesvirus is the etiologic agent in all 4variants. Cutaneous angiosarcoma is a cutaneous neoplasm with a very poor prognosis. It carries a high probability of local relapse and has a 10% to 15% survival rate at 5years. There are 3 main variants of cutaneous angiosarcoma: idiopathic angiosarcoma of the face and scalp; Stewart-Treves syndrome; and postradiation angiosarcoma. The only potentially curative treatment is surgery with or without radiotherapy. However, its indistinct borders and multicentric nature mean that treatment is often palliative with chemotherapy, radiotherapy, or both., (Copyright © 2018 AEDV. Publicado por Elsevier España, S.L.U. All rights reserved.)

Background: Breast angiosarcomas are rare neoplasm. Due to its rarity, our therapeutic strategy is extremely limited. Therefore, we investigated the clinicopathologic features and examined the treatment for angiosarcoma compared with some literatures., Methods: We conducted a retrospective chart and slide review of all patients in our division seen from 1997 to 2012 with a diagnosis of primary or secondary breast angiosarcoma at the National Cancer Center Hospital (Tokyo, Japan)., Results: Nine patients were diagnosed with breast angiosarcoma (six primary and three secondary cases). The median age of patients with primary angiosarcoma was 39 years (range 27-65 years). The median tumor size was 6.78 cm (range 3.0-8.8 cm). In the primary tumor, 4 patients had total mastectomy and 2 had a breast conserving surgery. 3- and 5-year disease-free survival (DFS) of the patients with primary angiosarcoma was 20 and 0 %. 5-year surviving rate of primary angiosarcoma was 50 %. In all patients with secondary angiosarcoma, recurrence was observed in all cases. But one case obtained long-term survival in local control therapy., Conclusions: Our study demonstrates breast angiosarcoma exhibits high recurrence rates. Tumor size and surgical margin may be important factor to obtain long-term survival. In this point of view, total mastectomy with adequate tumor margin with early detection is desired. In case of recurrence, if it is local, surgery may be potentially curative.

Background: Pancreatic involvement of angiosarcoma is extremely rare., Methods: We herein report a rare case of angiosarcoma associated with chronic lymphedema (Stewart-Treves syndrome) with pancreatic metastasis that was diagnosed using endoscopic ultrasound (EUS)/fine needle aspiration (FNA)., Results: A 43-year-old woman with a history of radical hysterectomy with bilateral inguinal lymphadenectomy and chemoradiotherapy for cervical cancer 15 years prior noticed the presence of erythematous indurative plaques on her right femoral region, where chronic lymphedema had developed. Contrast-enhanced computed tomography (CT) revealed not only multiple nodules in the subcutaneous tissue of the right femoral region but also a 25 mm × 20 mm solid mass in the region of the pancreatic tail. A histological analysis of the specimens obtained using EUS/FNA revealed angiosarcoma that was immunohistochemically positive for platelet/endothelial cell adhesion molecule-1 but negative for cytokeratin. The patient was diagnosed as Stewart-Treves syndrome that had metastasized to the pancreas. Chemotherapy was performed, but the patient died 14 months after her diagnosis., Conclusion: Unfortunately, this patient was not followed up, even though she had chronic lymphedema of the right femoral region due to the repeated occurrence of phlegmon. To improve the survival rate of this fatal secondary malignant complication of radical lymphadenectomy, an early diagnosis with consecutive and long-term clinical follow-up and close monitoring for Stewart-Treves syndrome is therefore important.

Lymphangiosarcoma (LAS) is an uncommon malignant neoplasia arising from lymphatic endothelium; little information exists regarding therapy. Single institutional retrospective review for canine LAS histopathology diagnoses over a 15-year period yielded 12 dogs. Ten dogs were presented for a mass and/or swelling at cervical, trunk or limb regions. Prior to diagnosis, 10 dogs received empiric wound therapy. Cytology performed in 10 consisted of mild inflammation. Survival ranged from 60, 168 and 876 days for three dogs with palliation; 90 days with prednisone in one; 182 days with chemotherapy in one; 240, 267, 487, 630 and 941 days for five receiving surgery; and 574 days for one receiving surgery, radiation and chemotherapy. One dog is alive with recurrence at 243 days following surgery and carboplatin chemotherapy. Clinical improvement existed in LAS dogs receiving multimodal therapies. Early tissue biopsies are recommended for progressive oedematous lesions of unknown origin., (© 2014 John Wiley & Sons Ltd.)

Angiosarcoma/lymphangiosarcoma is a rare malignancy with poor prognosis. We generated a mouse model with inducible endothelial-cell-specific deletion of Tsc1 to examine mTORC1 signaling in lymphangiosarcoma. Tsc1 loss increased retinal angiogenesis in neonates and led to endothelial proliferative lesions from vascular malformations to vascular tumors in adult mice. Sustained mTORC1 signaling was required for lymphangiosarcoma development and maintenance. Increased VEGF expression in tumor cells was seen, and blocking autocrine VEGF signaling abolished vascular tumor development and growth. We also found significant correlations between mTORC1 activation and VEGF, HIF1α, and c-Myc expression in human angiosarcoma samples. These studies demonstrated critical mechanisms of aberrant mTORC1 activation in lymphangiosarcoma and validate the mice as a valuable model for further study.

Classical Kaposi sarcoma (KS) usually appears on lower extremities accompanied or preceded by local lymphedema. However, the development in areas of chronic lymphedema of the arms following mastectomy, mimicking a Stewart-Treves syndrome, has rarely been described. We report an 81-year-old woman who developed multiple, erythematous to purple tumors, located on areas of post mastectomy lymphedema. Histopathological examination evidenced several dermal nodules formed by spindle-shaped cells that delimitated slit-like vascular spaces with some red cell extravasation. Immunohistochemically, the human herpesvirus type 8 (HHV-8) latent nuclear antigen-1 was detected in the nuclei of most tumoral cells confirming the diagnosis of KS. Lymphedema could promote the development of certain tumors by altering immunocompetence. Although angiosarcoma (AS) is the most frequent neoplasia arising in the setting of chronic lymphedema, other tumors such as benign lymphangiomatous papules (BLAP) or KS can also develop in lymphedematous limbs. It is important to establish the difference between AS and KS because their prognosis and treatment are very different. Identification by immunohistochemistry of HHV-8 is useful for the distinction between KS and AS or BLAP., (© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

A 7-year-old, 153.0-kg American Miniature mare presented for evaluation of keratoconjunctivitis of the right eye (OD). A superior palpebral conjunctival mass and stromal keratitis were diagnosed. The incisional biopsy diagnosis was a presumptive corneal hemangiosarcoma. Transpalpebral enucleation was performed, and histopathologic evaluation confirmed angiosarcoma of the conjunctiva, cornea, and extraocular muscles. The horse developed progressive epistaxis and orbital swelling following surgery. A systemic workup was performed 3 months after enucleation, revealing regrowth within the orbit and marked cranial cervical lymphomegaly, suggestive of metastasis. Humane euthanasia was performed, and necropsy confirmed a locally invasive periorbital tumor with metastasis to the submandibular tissue, submandibular lymph node, and thoracic inlet. Histopathologic evaluation of necropsy specimens revealed polygonal to spindle neoplastic cells lining neoplastic vascular channels lacking erythrocytes. Immunohistochemically, the neoplastic cells labeled strongly positive for PROX-1, vimentin, CD-31, VEGF, weakly positive for factor VIII-related antigen, and negative for collagen IV. Based on the clinical, histological, and immunohistochemical features of this tumor, a primary ocular lymphangiosarcoma with metastasis was diagnosed., (© 2015 American College of Veterinary Ophthalmologists.)

A 12-year-old mixed-breed neutered female dog was referred with cutaneous tumors at the left auricle. Histologically, the cutaneous tumor located in the dermis comprised numerous clefts and cavernous channels lined by neoplastic endothelial cells with no erythrocytes. Bone tissue without direct contact with neoplastic cells was seen in the well-developed stromal connective tissue. The neoplastic endothelial cells exhibited mild to moderate atypia. Immunohistochemically, neoplastic cells were positive for vimentin and negative for cytokeratin and factor VIII-related antigen. Basement membrane around the neoplastic lumens was positive for laminin in a linear or granular pattern. Ultrastructural examination revealed discontinuous basement membrane beneath the tumor cells. Histopathological features of this case were consistent with lymphangiosarcoma, and stromal ossification was characteristic.

Stewart-Treves Syndrome is characterized by the presence of lymphangiosarcoma on limb extremities. Rare, it occurs in 0.5% of patients who have undergone radical mastectomy with axillary node dissection. The main cause is chronic lymphedema with endothelial and lymphatic differentiation, with no direct relationship to breast cancer. Seven years after a radical right-side mastectomy with lymph node dissection and adjuvant therapy, the patient developed a lesion on her right arm. The dermatological examination revealed an erythematous nodule with bleeding surface on chronic right forearm lymphedema. After the biopsy, a lymphangiosarcoma on chronic lymphedema was diagnosed. Infrequent, this syndrome is relevant because of its associated mortality. Early diagnosis is important to improve survival and reduce complications.

Stewart-Treves syndrome is a rare cutaneous angiosarcoma that develops in long-standing chronic lymphedema. Though most commonly this angiosarcoma is a result of post mastectomy lymphoedema, it also develops in Milroy disease, idiopathic, congenital, traumatic and filarial lymphoedema. Despite the rarity of this syndrome and its poor prognosis, early diagnosis associated with radical surgery can provide improved survival. We report a case of angiosarcoma in the lower limb in a patient with chronic lymphedema associated with history of repeated erysipela episodes.

A 4-year-2-month-old female Japanese domestic cat was diagnosed with lymphangiosarcoma through tissue biopsy of an amputated leg. Two months later, the cat was euthanized, and postmortem findings revealed edema, and bruising at the caudal region of the trunk, pulmonary hemorrhage, pulmonary nodules and mediastinal lymphadenopathy. Microscopically, neoplastic tissues were observed in the dermis and subcutis of the trunk, lung, mediastinal lymph nodes, diaphragm, omentum and mesentery. The tumor cells were spindle to polygonal-shaped with nuclear pleomorphism aligning along pre-existing collagen bundles and forming irregular vascular channels in which the erythrocytes were rarely observed. These cells were immunopositive for vimentin, von Willebrand factor and CD31. Based on the histopathological and immunohistochemical features, the neoplasia was diagnosed as lymphangiosarcoma with systemic metastases.

Lymphangiosarcoma is a rare malignant neoplasm of endothelial cells. The term is used to describe an angiosarcoma associated with chronic lymphedema. The skin of the head and neck region is the most common site of origin. Rather few cytogenetic studies on lymphangiosarcoma are reported in the literature. We here describe a case of an 87-year-old woman, with a history of recurring lymphangitis and with an ulcerated nodular lesion of the leg. The histological diagnosis was a malignant neoplasm of vascular origin, with the morphological and immunohistochemical features of a lymphangiosarcoma. A series of antibodies (CD31, CD34, vimentin, podoplanin and HHV-8), conventional and molecular cytogenetic and Spectral Karyotyping (SKY-FISH) analyses were used to study this case. The immunohistochemical evaluation revealed that the neoplasm was positive for vimentin, CD31, CD34 and podoplanin and negative for HHV-8. The proliferation rate (Ki-67) was about 70%. Karyotype was defined using conventional cytogenetic and SKY-FISH. In addition, high-level of amplification was observed with MYC split signal probe. The morphological and immunohistochemical evaluations supported the diagnosis of lymphangiosarcoma. Moreover, the cytogenetic and molecular findings contributed towards accurately defining the karyotypic aberrations of this rare sarcoma., (Copyright © 2014 Elsevier GmbH. All rights reserved.)

This 17-year-old woman had chronic congenital lymphedema in the left lower extremity since childhood. She underwent surgeries to remove excessive lymphedematous tissues more than 15 times previously. Histopathology of the specimen from the recent surgery revealed angiosarcoma; therefore, FDG-PET/CT scan was arranged to determine the extent of tumor spread, and distant metastases were discovered. Stewart-Treves syndrome is angiosarcomas that arise secondary to chronic lymphedema. Because of the high lethality of this condition, the FDG-PET/CT scan may be a clinically useful imaging modality to detect the possible malignant transformation earlier for patients with chronic lymphedema.

Benign lymphangioendothelioma (BL) represents a very rare lymphatic vascular proliferation. Our aim is to be aware that owing to its characteristic features, pathologists can easily misinterpret it as cutaneous low-grade angiosarcoma when examining only small specimens. In the present case, multiple small and yellowish to reddish soft nodules were noticed in the edematous left arm of a 54-year-old Japanese female 4 years after the radical mastectomy with axillary lymph nodes dissection and following radiotherapy to the chest for the left breast carcinoma. The biopsy specimen showed an ill-defined lesion composed of a proliferation of irregular and sometimes anastomosing vascular structures in the dermis, lined by endothelial cells having mildly hyperchromatic and pleomorphic nuclei, but no mitotic figures. As the lesion grew within deeper dermis, these proliferating vessels dissected dermal collagenous bands, occasionally arranged in low-papillary projections and/or characteristic hobnail cytomorphology. We first interpreted it as low-grade angiosarcoma following chronic lymphedema due to the operation, i.e., the so-called Stewart-Treves syndrome. Although additional treatments were performed for 7 years, she had neither local invasion nor metastases of these tumors, respectively, and was alive and well. Retrospective immunohistochemical findings demonstrated that these mildly atypical endothelial cells were strongly positive for lymphatic vessel endothelial hyaluronan receptor (LYVE)-1 as well, and MIB-1 labeling index was less than 1%. Therefore, we finally made a diagnosis of BL of the skin. MIB-1 labeling index might be useful and adjunctive aids for reaching the correct diagnosis of cutaneous BL, especially in case of small or inadequate specimens.Virtual Slides: The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/13000_2014_197.

The Stewart-Treves syndrome was first described in 1948, it's an angiosarcoma developed on a longstanding lymphadenomatous limb, more often after radical mastectomy. Diagnosis is made on skin biopsy and the prognosis is poor when radical surgery can't be performed. We report the case on a Stewart-Treves syndrome in a sixty-six years old woman who underwent radical mastectomy for breast carcinoma ten years earlier. Surgery was not feasible at the time of diagnosis, and we lost touch of the patient even if chemotherapy was decided. Radical surgery is the best treatment to date for this rare disease. Conservative surgery with adjuvant radiotherapy is also possible. Systemic chemotherapy is reserved for locally advanced unresectable and metastatic forms. We advocate long term follow-up for every post mastectomy lymphedema to diagnosis this fatal disease when curable.

Background: Lymphangiosarcoma is a rare, aggressive malignancy that originates from the endothelial cells lining lymphatic vessels and carries an extremely poor prognosis. Its clinical and histologic features are often indistinguishable from angiosarcoma., Objective: We sought to better characterize the clinical and histologic features of lymphangiosarcoma., Methods: Case report and review of the literature., Results: A number of immunohistochemical markers, including Von Willebrand factor, Ulex europaeus agglutinin 1, CD31, VEGFR-3, D2-40, Prox-1, can be used to help differentiate lymphatic from vascular tissue., Conclusions: Recent characterization of several new biologic markers has allowed greater differentiation between these tumors and may provide new therapeutic targets for treatment.

Angiosarcomas account for less than 0.05% of the malignant neoplasms of the breast. We present here 7 cases of malignant vascular neoplasms of the breast, including 2 cases of postmastectomy Stewart-Treves syndrome. In this case series, most of the patients were young. Tumour was bilateral at presentation in one case. The size of the tumours ranged from 1.6 cm to 11 cm. Although breast angiosarcomas are rare neoplasms, with the increasing use of radiation therapy for breast cancer patients, post-radiation skin lesions should not be ignored.

Background: The development of angiosarcoma in oedematous tissue is referred to as Stewart-Treves syndrome (STS). This rare and fatal complication is associated with chronic post mastectomy lymphoedema and radiotherapy for breast cancer. Angiosarcoma spread is facilitated by the formation of blood vessels (angiogenesis) and lymph vessels (lymphangiogenesis). In the future antiangiogenic therapy may improve the poor outcome of current treatments. There was evidence that blocking the angiogenenesis would inhibit progression of angiosarcoma. It seems reasonable to hypothesize that blocking the lymphangiogenesis may yield similar results. Although angiosarcomas commonly derive from blood vessels, in case of STS angiosarcomas chronic lymphoedema may suggest its lymphatic origin. The goal of this study was to visualize interstitial space and lymphatics in the central and peripheral regions of STS angiosarcoma., Methods: On tissue samples obtained from STS angiosarcoma we have performed: first colour stereoscopic lymphography to visualise the morphology of lymphatic vessels and extracellular spaces, second immunohistochemical staining specific for lymphatic vessels endothelium (LYVE-1) and blood endothelial cells (CD31, factor VIII) and prolymphangiogenic vascular endothelial growth factor (VEGF-C) for precise identification of lymphatic endothelia. STS angiosarcoma morphology was assessed by comparison of pictures obtained on lymphography, microscopy and confocal microscopy., Results: STS angiosarcomas present heterogenous morphology with areas dominated by hemangiosarcoma and lymphangiosarcoma structures. STS angiosarcoma expressed phenotypes of both blood and lymphatic endothelia. LYVE-1 and VEGF-C is expressed by STS angiosarcoma and may be used to discriminate tumour differentiation. Morphology of lymphatic vessels and spaces in the tumour suggest absence of their normal lymphatic function., Conclusions: Our results confirmed both hemangio- and lymphangiogenic origin of STS angiosarcoma. Expression of VEGF-C makes STS angiosarcoma a good candidate for targeted antilymphangiogenic therapy. However, morphology of intratumoral lymphatics on colour lymphography suggested their impaired function, which can hamper drug distribution.

Case Description: A 5-year-old sexually intact male Giant Schnauzer was evaluated because of difficulty breathing and left pelvic limb swelling. Eighteen months previously, the patient had had intermittent left pelvic limb swelling, but the owner declined further testing at that time., Clinical Findings: Physical examination revealed severe pitting edema of the left pelvic limb and prepuce and muffled heart sounds on thoracic auscultation. Results of thoracic radiography and thoracocentesis were consistent with chylothorax, and CT imaging of the thorax and abdomen revealed a mass involving the whole left sublumbar area., Treatment and Outcome: In an attempt to treat the chylothorax, pleural omentalization and pericardectomy were performed. Histologic evaluation of several biopsy specimens harvested in the abdominal and thoracic cavities revealed disseminated lymphangiosarcoma. The patient recovered well from surgery, and mitoxantrone chemotherapy was administered. As of 10 months after surgery, the dog was clinically normal except for mild pelvic limb edema., Clinical Relevance: The combination of clinical signs, multiple imaging features, surgical findings, and histologic examination findings enabled the final diagnosis of lymphangiosarcoma. Clinical management that included medical and surgical treatments and chemotherapy resulted in improved quality of life and extended survival time in a dog with metastatic lymphangiosarcoma.

The concept of "lymphangiosarcoma" remains obscure. Therefore, we reported a patient with lymphangiosarcoma, resistant to immunotherapy. The patient presented with impressive and discriminative features: clinically an ill-defined edematous lesion with lymphorrhea and pathologically atypical vascular channel formation without extravasation of blood, clearly distinguished from common angiosarcoma with hemorrhage. From this case, a lymphangiosarcoma cell line, MO-LAS, was established and its characteristics were compared with the hemangiosarcoma cell line, ISO-HAS. Flow cytometric analysis revealed that MO-LAS was negative for factor VIII-related antigen, but positive for CD31, D2-40, NZ-1, and vascular endothelial growth factor receptor-3 (VEGFR-3), similar to ISO-HAS. However, MO-LAS expressed a much higher level of homeobox gene PROX1, indicating a lymphatic phenotype, compared with ISO-HAS. Furthermore, MO-LAS showed a much lesser expression of oncogenes and much lower sensitivity against lymphokine-activated killer (LAK) cells. Lymphangiosarcoma may be difficult to recognize by the immune system. Conclusively, the establishment of MO-LAS, a novel angiosarcoma cell line bearing lymphatic characters, strongly suggests the entity of lymphangiosarcoma.