Basal cell carcinoma in situ of the skin revisited: case reports of the superficial type and fibroepithelioma type of this in situ cutaneous neoplasm.

Cutaneous basal cell carcinoma in situ is a recently proposed subtype of this skin cancer. It is characterized by either restriction of the tumor cells within the epidermis or the presence of tumor cells contiguous with the overlying epidermis that extend into the underlying dermis, or both. Importantly, cancer invasion-demonstrated by non-contiguous aggregates of basaloid tumor cells in the dermis-is not a feature of in situ basal cell carcinoma of the skin. A 63-year-old woman with cutaneous basal cell carcinoma in situ-superficial type that presented as an erythematous scaly plaque on her abdomen and a 61-year-old man with a cutaneous basal cell carcinoma in situ-fibroepithelioma type that presented as a flesh-colored smooth exophytic nodule on his back are reported. The characteristics of in situ basal cell carcinoma of the skin in these individuals are summarized. In conclusion, similar to other cutaneous malignant neoplasms-such as squamous cell carcinoma, malignant melanoma, and Merkel cell carcinoma-basal cell carcinoma of the skin can also present as an in situ cancer.

An integrative approach for exploring the nature of fibroepithelial neoplasms.

BACKGROUND: Malignant phyllodes tumour (MPT) is a rare breast malignancy with epithelial and mesenchymal features. Currently, there are no appropriate research models or effective targeted therapeutic approaches for MPT. METHODS: We collected fresh frozen tissues from nine patients with MPT and performed whole-exome and RNA sequencing. Additionally, we established patient-derived xenograft (PDX) models from patients with MPT and tested the efficacy of targeting dysregulated pathways in MPT using the PDX model from one MPT. RESULTS: MPT has unique molecular characteristics when compared to breast cancers of epithelial origin and can be classified into two groups. The PDX model derived from one patient with MPT showed that the mouse epithelial component increased during tumour growth. Moreover, targeted inhibition of platelet-derived growth factor receptor (PDGFR) and phosphoinositide 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) by imatinib mesylate and PKI-587 showed in vivo tumour suppression effects. CONCLUSIONS: This study revealed the molecular profiles of MPT that can lead to molecular classification and potential targeted therapy, and suggested that the MPT PDX model can be a useful tool for studying the pathogenesis of fibroepithelial neoplasms and for preclinical drug screening to find new therapeutic strategies for MPT.

Giant juvenile fibroadenomas with and without prominent pseudoangiomatous stromal hyperplasia (PASH)-like change: clinicopathological and molecular characteristics.

AIMS: Juvenile fibroadenomas (JFA) are biphasic fibroepithelial lesions (FEL) usually occurring in adolescent female patients. Giant (G) JFA, like other FEL, may exhibit prominent pseudoangiomatous stromal hyperplasia (PASH)-like change. We sought to determine clinicopathological and molecular characteristics of GJFA with and without PASH. METHODS AND RESULTS: Archives were searched for cases of GJFA (1985-2020). All were stained for androgen receptor (AR), beta-catenin, CD34 and progesterone receptor (PR). Cases were sequenced using a custom 16-gene panel - MED12 (exons 1 and 2), TERT promoter (-124C>T and -146Ctable>T), SETD2, KMT2D, RARA (exons 5-9), FLNA, NF1, PIK3CA (exons 10, 11 and 21), EGFR, RB1, BCOR, TP53, PTEN, ERBB4, IGF1R and MAP3K1. Twenty-seven GJFA from 21 female patients aged 10.1-25.2 years were identified. Size ranged from 5.2 to 21 cm. Two patients had multiple, bilateral and later recurrent GJFA. Thirteen (48%) cases showed prominent PASH-like stroma. All were positive for stromal CD34, negative for AR and beta-catenin and one case showed focal PR expression. Sequencing showed MAP3K1 and SETD2 mutations in 17 samples, with KMT2D, TP53 and BCOR aberrations in 10 (45%), 10 (45%) and seven (32%) cases, respectively. Tumours with a PASH-like pattern had higher prevalence of SETD2 (P = 0.004) and TP53 (P = 0.029) mutations, while those without PASH had more RB1 mutations (P = 0.043). MED12 mutation was identified in one case. TERT promoter mutation was observed in four (18%), including two recurrences. CONCLUSIONS: Gene mutations along more advanced phases of the proposed FEL pathogenetic pathway in GJFA are unusual, and suggest a mechanism for more aggressive growth in these tumours.

RB1 loss in the mesenchymal component of onychomatricoma.

BACKGROUND: Onychomatricoma is a nail neoplasm that usually presents as longitudinal nail plate thickening, involving either the partial or whole nail. Histopathologically, it is characterized by deep invaginations of the proliferating nail matrix and proliferation of CD34+ and CD10+ spindle cells with collagenous to myxoid stroma. Onychomatricoma has been considered a fibroepithelial neoplasm. Recently, RB1 loss has been verified using array comparative genomic hybridization. METHODS: This study investigated the RB1 status in onychomatricoma with morphological methods. RESULTS: Six patients with onychomatricoma were included in the study. RB1 status was assessed using immunohistochemical staining and fluorescence in situ hybridization. Immunohistochemical staining showed that all six cases experienced RB1 loss in the mesenchymal component of onychomatricoma but not in the proliferated nail matrix. Fluorescence in situ hybridization in five cases showed a monoallelic deletion of the RB1 locus in the mesenchymal component but not in the proliferated nail matrix. CONCLUSIONS: RB1 loss was observed only in the mesenchymal component of onychomatricoma. Our findings suggest that the proliferated nail matrix in onychomatricoma represents reactive hyperplasia of various degrees secondary to neoplastic mesenchymal proliferation. This indicates that onychomatricoma should be recognized as an RB1-deleted soft tissue neoplasm rather than a fibroepithelial neoplasm.

[Pathological features and clinicopathological significance of TERT promoter mutation in breast fibroepithelial tumors without definite diagnosis].

Objective: To investigate the pathological features and the clinicopathological significance of TERT detection in those tumors that were difficult to diagnosis. Methods: A total of 93 cases of fibroepithelial tumors without definite diagnosis were collected from the Affiliated Hospital of Qigndao University between 2013 and 2021. The clinical details such as patients' age and tumor size were collected. All slides were re-reviewed and the pathologic parameters, including stromal cellularity, stromal cell atypia, stromal cell mitoses, and stromal overgrowth were re-interpreted. Sanger sequencing was used to detect TERT promoter status, and immunohistochemistry was performed to detect TERT protein expression. The relationship between TERT promoter mutation as well as protein expression levels and the clinicopathological parameters were also analyzed. Results: The patients' ages ranged from 30 to 71 years (mean of 46 years); the tumor size ranged from 1.2 to 8.0 cm (mean 3.8 cm). These tumors showed the following morphologic features: leafy structures in the background of fibroadenoma, or moderately to severely abundant stromal cells. The interpretations of tumor border status were ambiguous in some cases. The incidence of TERT promoter mutation was high in patients of age≥50 years, tumor size≥4 cm, and stromal overgrowth at ×4 or ×10 objective, and these clinicopathologic features were in favor of diagnosis of phyllodes tumors. TERT protein expression levels was not associated with the above clinicopathologic parameters and its promoter mutation status. Conclusions: The diagnostic difficulty for the breast fibroepithelial tumors is due to the difficulty in recognition of the leafy structures or in those cases with abundant stromal cells. A comprehensive evaluation combined with morphologic characteristics and molecular parameters such as TERT promoter may be helpful for the correct diagnosis and better evaluating recurrence risk.

Computer-Aided Detection of Quantitative Signatures for Breast Fibroepithelial Tumors Using Label-Free Multi-Photon Imaging.

Fibroadenomas (FAs) and phyllodes tumors (PTs) are major benign breast tumors, pathologically classified as fibroepithelial tumors. Although the clinical management of PTs differs from FAs, distinction by core needle biopsy diagnoses is still challenging. Here, a combined technique of label-free imaging with multi-photon microscopy and artificial intelligence was applied to detect quantitative signatures that differentiate fibroepithelial lesions. Multi-photon excited autofluorescence and second harmonic generation (SHG) signals were detected in tissue sections. A pixel-wise semantic segmentation method using a deep learning framework was used to separate epithelial and stromal regions automatically. The epithelial to stromal area ratio and the collagen SHG signal strength were investigated for their ability to distinguish fibroepithelial lesions. An image segmentation analysis with a pixel-wise semantic segmentation framework using a deep convolutional neural network showed the accurate separation of epithelial and stromal regions. A further investigation, to determine if scoring the epithelial to stromal area ratio and the SHG signal strength within the stromal area could be a marker for differentiating fibroepithelial tumors, showed accurate classification. Therefore, molecular and morphological changes, detected through the assistance of computational and label-free multi-photon imaging techniques, enable us to propose quantitative signatures for epithelial and stromal alterations in breast tissues.

Malignant phyllodes tumor of the breast: a systematic review.

Phyllodes tumors (PT) are fibroepithelial neoplasms of the breast showing a peculiar leaf-like appearance. They account for 0.3 to 1% of all primary breast tumors and 2.5% of all fibroepithelial breast tumors. PT are classified into benign, borderline and malignant based upon their stromal morphology with a distribution of 60%, 20%, and 20%, respectively. Malignant PT of the breast constitute an uncommon challenging group of fibroepithelial neoplasms. They have a relatively high tendency to recur, although distant metastasis is uncommon, and nearly exclusive to malignant PT. Adequate surgical resection remains the standard approach to achieve maximal local control. Giant malignant PT are rare and a pose a diagnostic dilemma for pathologists, especially when comprised of sarcomatous elements. This review highlights the morphological features of PT detected in cytology and histology specimens and discusses diagnostic pitfalls and differential diagnosis.

Fibroepithelial lesions revisited: implications for diagnosis and management.

Fibroepithelial lesions of the breast, comprising the fibroadenoma and phyllodes tumour, are a unique group of neoplasms that share histological characteristics but possess different clinical behaviour. The fibroadenoma is the commonest benign breast tumour in women, while the phyllodes tumour is rare and may be associated with recurrences, grade progression and even metastasis. The diagnosis of fibroadenoma is usually straightforward, with recognised histological variants such as the cellular, complex, juvenile and myxoid forms. The phyllodes tumour comprises benign, borderline and malignant varieties, graded using a constellation of histological parameters based on stromal characteristics of hypercellularity, atypia, mitoses, overgrowth and the nature of tumour borders. While phyllodes tumour grade correlates with clinical behaviour, interobserver variability in assessing multiple parameters that are potentially of different biological weightage leads to significant challenges in accurate grade determination and consequently therapy. Differential diagnostic considerations along the spectrum of fibroepithelial tumours can be problematic in routine practice. Recent discoveries of the molecular underpinnings of these tumours may have diagnostic, prognostic and therapeutic implications.

HMGA2 Is a Useful Marker of Vulvovaginal Aggressive Angiomyxoma But May Be Positive in Other Mesenchymal Lesions at This Site.

Aggressive angiomyxoma (AA) is a rare mesenchymal neoplasm occurring almost exclusively in the vulvovaginal region and which has a wide differential diagnosis. It has previously been suggested that the nuclear transcription factor HMGA2 is a useful marker of AA, although the number of studies is limited. We investigated HMGA2 immunoreactivity in a large series (n=284) of vulvovaginal mesenchymal lesions. HMGA2 nuclear staining was classified as diffuse (≥50%), focal (<50%), or negative. Of 38 cases of AA, 26 (68%) were positive; 77% (n=20) of these exhibited diffuse staining. Of the 41 smooth muscle tumors, 18 (44%) were positive with 16 (89%) exhibiting diffuse staining. 80 fibroepithelial stromal polyps were included and 15 (19%) were positive (8 diffuse; 7 focal). Most of the fibroepithelial stromal polyps that exhibited diffuse HMGA2 immunoreactivity were large and edematous. Occasional cases of a variety of other lesions were positive, including 1 of 30 superficial myofibroblastomas and 1 of 16 angiomyofibroblastomas. Cellular angiofibromas (n=12) and superficial angiomyxomas (n=6) were always negative. Our results confirm that HMGA2 is a useful marker of AA but a significant minority of cases are negative. The marker also lacks specificity, since a high percentage of smooth muscle tumors are positive, although these typically do not bear a close morphologic resemblance to AA. A novel observation in our study is positive staining of some fibroepithelial stromal polyps, particularly when large and edematous; these are particularly likely to be confused morphologically with AA and positive staining with HMGA2 represents a significant diagnostic pitfall.

MED12 exon 2 and TERT promoter mutations in primary and recurrent breast fibroepithelial lesions.

The genetic alterations in the recurrent breast fibroepithelial tumors are poorly understood. In the present study, we aimed to investigate mediator protein complex subunit 12 (MED12) exon 2 and telomerase reverse transcriptase (TERT) promoter mutations in a series of primary and recurrent fibroepithelial tumors. Sanger sequencing for MED12 exon 2 and TERT promoter was performed in 26 pairs of primary and recurrent fibroepithelial tumors (19 pairs of phyllodes tumors and seven pairs of fibroadenomas). The relationship between the genotypes and clinicopathological variables was also analyzed. MED12 mutation was identified in 19 primary tumors (12 phyllodes tumors and 7 fibroadenomas) and 17 recurrences (14 phyllodes tumors and three fibroadenomas). Most recurrent phyllodes tumors retained the original MED12 variants (17/19). Six recurrent fibroadenomas showed different MED12 variants from their paired primary tumors (6/7). TERT promoter mutation was identified in 13 primary phyllodes tumors (13/19) and 15 recurrent phyllodes tumors (15/19). However, it was only identified in one primary fibroadenoma (1/7). Recurrent phyllodes tumors often retained the original MED12 and TERT promoter mutations, while recurrent fibroadenomas often acquired new MED12 mutations. Our findings suggest that recurrent phyllodes tumors may be "true recurrence," and TERT mutant "benign fibroepithelial tumors" should be treated as phyllodes tumors.

Characteristic Clinicopathological Features of Secondary Extramammary Paget Disease With Underlying Anorectal Adenocarcinoma: Evenly Circumferential Perianal Distribution, Fibroepithelioma of Pinkus-like Changes, and Subepidermal Mucin Deposits Without Invasive Tumor Cells.

ABSTRACT: This study aimed to identify the clinical and histopathological characteristics of secondary extramammary Paget disease (EMPD) with underlying anorectal adenocarcinoma so as to differentiate it from primary cutaneous EMPD. Seventeen and 8 cases of primary and secondary EMPD with anorectal adenocarcinoma, respectively, were retrieved from the pathology archive and the clinical and histopathological features reviewed. The tumor samples from 21 cases were totally resected specimens, whereas 3 and 1 of secondary and primary cases were punch biopsied, respectively. All 8 (100%) cases of secondary EMPD presented evenly distributed perianal lesions. By contrast, 4 of 17 (23.5%) primary EMPD cases had perianal skin lesions and displayed an uneven, asymmetrical distribution around the anus. Fibroepithelioma of Pinkus-like changes and subepidermal mucin deposits with no or few invasive tumor cells were observed in 6 (75%) and 3 (37.5%) of the 8 secondary EMPD cases, respectively, although 3 secondary case samples were small biopsy specimens. Both the histopathological changes were not observed in any of the 17 primary EMPD cases. Evenly circumferential perianal distribution, fibroepithelioma of Pinkus-like changes, and subepidermal mucin deposits without invasive tumor cells were characteristic to cases of secondary EMPD with anorectal adenocarcinoma. These clinicopathological features could be used to differentiate between secondary and primary EMPD.

Morphologic, Immunohistochemical, and Molecular Distinction Between Fibroepithelioma of Pinkus and "Fenestrated" Basal Cell Carcinoma.

Fibroepithelioma of Pinkus (FEP) is a rare cutaneous neoplasm with a characteristic fenestrated architecture and a prominent spindle cell stromal component and which invariably pursues an indolent course. The classification of FEP has been much debated since its first description in 1953, with some arguing that it represents a variant of a basal cell carcinoma (BCC) while others view it as a variant of a trichoblastoma. Multiple previous immunohistochemical studies aiming to clarify this issue have yielded conflicting results. To date, there have been no molecular studies of FEP. We identified 16 cases of fenestrated follicular neoplasms and classified them as BCC or FEP based solely on histomorphologic criteria. CK20 immunohistochemistry supported this classification scheme, with FEP showing significantly more CK20-positive Merkel cells than BCC. We then analyzed a subset of these tumors by a targeted next-generation DNA sequencing platform. All the BCC cases harbored pathogenic PTCH1 mutations, confirming the diagnosis. By contrast, none of the FEP cases harbored a PTCH1 mutation or indeed any mutation known to be causally linked to the development of BCC. Our results suggest that FEP can be distinguished from BCC on morphologic, immunohistochemical, and molecular genetic grounds. We argue that FEP is better considered a benign follicular neoplasm and support its classification as a variant of trichoblastoma.

The role of insulin-like growth factor in Acrochordon Etiopathology.

BACKGROUND: There are reports that acrochordon (skin tag), the most common fibroepithelial tumor of the skin, may be associated with metabolic syndrome components, particularly insulin metabolism disorders. However, to the best of our knowledge, there is no study examining its association with insulin resistance and tissue levels of insulin-like growth factor 1 receptor (IGF-1R) and insulin-like growth factor 2 receptor (IGF-2R). METHODS: Thirty patients with at least one acrochordon in their body who had no known history of diabetes mellitus and a control group comprised 30 individuals who had no acrochordon or no known history of diabetes mellitus were included. The tissue expression of IGF-1R and IGF-2R were investigated via immunohistochemical assessment in both groups. RESULTS: In the group with acrochordon, IGF-1R and IGF-2R expression was found to be significantly higher compared to the control group (p < 0,01). Using logistic regression analysis, an increase in serum insulin, serum IGF-1 and HOMA-IR levels was found to be associated with the expression levels of IGF-1R and IGF-2R. CONCLUSION: These findings support the view that insulin metabolism disorders should be evaluated in patients with acrochordon. Our study indicates that IGF receptors may have an effect on acrochordon pathogenesis and that acrochordon etiology and related conditions can be clarified by detection of parameters that influence receptor levels.

Accuracy and clinical implications of pre-operative breast core needle biopsy diagnoses of fibroepithelial neoplasms and sarcomatoid carcinomas.

PURPOSE: Accurate classification of breast phyllodes tumors (PTs) on core biopsy can be challenging. The differential diagnosis of benign PT (BP) is fibroadenoma (FA), whereas the differential diagnosis of malignant PT (MP) is sarcomatoid (metaplastic) carcinoma (SC). METHODS: Here, we compare the pre-excision core biopsy diagnosis and clinicopathologic features of histologically confirmed MP, borderline PT (BLP), BP, FA, and SC. Consecutive cases of 34 histologically confirmed PT (14 MP, 10 BLP, 10 BP), 13 SC, and 10 FA were identified. RESULTS: A core biopsy diagnosis of SC was made only in SC (77%, p = 0.003). The diagnosis "malignant neoplasm" or "atypical spindle cell neoplasm" was made in 100% MP and 23% SC, but no other tumor (p = 0.0001). The diagnosis "phyllodes tumor" was made only in PT (44% BLP, 11% BP, p = 0.06). The diagnosis "fibroepithelial lesion" was made in 44% BLP, 67% BP, and 29% FA. The diagnosis "FA" was made most commonly in FA (57%) (versus 22% BP and no other tumor; p = 0.002). Neoadjuvant therapy was given only in SC (23%, p = 0.03); adjuvant therapy was given in 46% SC and 13% MP (p = 0.04). CONCLUSIONS: A pre-operative core biopsy diagnosis of "malignant spindle cell neoplasm" separates MP and SC from BLP, BP, and FA. However, MP and SC can have overlapping features on core biopsy. Thus, one must be careful not to overcall SC on core biopsy, as patients diagnosed with SC may receive neoadjuvant therapy. A core biopsy diagnosis of "phyllodes tumor" is specific for PT and can guide treatment planning of a wide local excision.

Molecular insights into paediatric breast fibroepithelial tumours.

AIMS: This study aims to examine the molecular genetics of paediatric breast fibroepithelial tumours through the targeted sequencing of 50 genes. METHODS AND RESULTS: Formalin-fixed paraffin-embedded tissues of fibroepithelial tumours diagnosed in a cohort of patients aged 18 years and below were subjected to next generation sequencing using the Haloplex Target Enrichment System. Twenty-five conventional and 17 juvenile fibroadenomas were studied, with MED12 mutations found in 53.8 and 35% of the tumours, respectively. There was also one benign fibroepithelial neoplasm with hybrid features of juvenile papillomatosis and infarcted benign phyllodes tumour-like areas. Most tumours did not have mutations in well-known cancer driver genes, none harboured TERT promoter mutations, while 25.6% (11 of 43) showed no mutations. Metachronous and synchronous tumours were found to have mutational heterogeneity with some containing mutations in MED12; other genes or no mutations were detected at all. Four of eight giant fibroadenomas (size 5 cm or larger) had no mutations detected, suggesting that there are other molecular mechanisms driving their growth. Tumours with MED12 mutations incidentally had a significantly higher stromal mitotic count compared with those without. CONCLUSION: While paediatric fibroepithelial lesions can have cellular stroma potentially raising concern for phyllodes tumour, their lack of TERT promoter and cancer driver mutations is reassuring. The absence of mutations in a significant proportion of tumours, especially the giant fibroadenomas, warrants investigation of pathogenetic mechanisms beyond those involving the 50 genes.

Fibroepithelial Stromal Polyp of the Vulva: Case Report and Review of Potential Histologic Mimickers.

Vulvar tumors arising from submucosal connective tissue, some of which exhibit hormonal responsiveness, have many clinical and histologic overlapping characteristics. We present a case of a fibroepithelial stromal polyp arising from the vulva of a 22-year-old female. We review the differential diagnosis with an emphasis on distinguishing features of these uncommon neoplasms. Accurate diagnosis is essential as the extent of surgical resection and risk of local recurrence varies for these tumors.

Giant fibroepithelial polyp of the thigh and retroperitoneal fibromatosis in a young woman: a rare case.

We present a case of 20-year-old woman who presented with a large pedunculated skin covered mass lesion arising from the left thigh, measuring 40 × 25 cm, with no history of pain or skin ulceration and a feeling of a lump with dragging pain in the left side of the abdomen for about 7 years. Subsequently, ultrasound, contrast-enhanced computed tomography, and magnetic resonance imaging of abdomen and left thigh region were carried out. The lesion was broad-based toward the left upper thigh with a central core of interspersed fat supplied by branches of the superficial and deep femoral arteries. Another lesion was seen in the left retroperitoneum anterior to the psoas muscle in a left paravertebral location encasing the left common iliac vessels extending into the left pelvic cavity and inguinal region inferiorly. The lesion showed dense post-acoustic shadowing on ultrasound, mild enhancement on contrast-enhanced computed tomography, and appeared hypointense on T1- and T2-weighted images. A left thigh lesion was excised, whereas incisional biopsy was done for the left retroperitoneal lesion. The diagnosis of a giant fibroepithelial polyp arising from the left thigh and left retroperitoneal fibromatosis was made. This is the first report of such a giant fibroepithelial polyp arising from the thigh with associated retroperitoneal fibromatosis.

Les difficultés du diagnostic : du carcinome basocellulaire aux tumeurs trichoblastiques: From basal cell carcinoma to trichoblastic tumors: a diagnostic challenge.

Basal cell carcinoma (BCC) is a very common tumor, of which the diagnosis is generally easy. Clinical prediction of histopathological subtype however is however often difficult, i.e. the majority of sclerosing BCCs believed to be morpheaform are in fact trabecular or nodular. There is a subgroup of aggressive BCCs, including trabecular (the most common), morpheaform (rare) and micronodular (very rare) subtypes. Differentiating trichoblastoma from BCC is not always easy, but there are distinctive histopathologic criteria and preferential expression of Berp4 in BCC and PHLDA1 in trichoblastoma that may be of help. The group of trichoblastic tumors comprises giant but benign trichoblastomas and trichoblastic carcinomas at the end of the spectrum (of low or high grade). In case of metastatic BCC, one must rule out trichoblastic carcinoma. Morphologic variants of BCC such as pigmented, clear cell, granular cell BCC or BCC with areas of keratinisation are not of poorer prognosis than the classic types. On the opposite, BCC with sebaceous differentiation (in fact sebaceomas) belong to the spectrum of tumors found in Muir-Torre and must be identified. Basosquamous BCCs should be treated like squamous cell carcinomas as they are more aggressive than the nodular subtype. Cet article fait partie du numéro supplément Prise en charge des carcinomes basocellulaires difficiles à traiter réalisé avec le soutien institutionnel de Sun Pharma.

Polypoid arteriovenous malformation of the ureter mimicking a fibroepithelial polyp, a case report.

BACKGROUND: Arteriovenous malformations (AVM) of the urinary tract are extremely rare. To the best of our knowledge, only three case of AVM of the ureter have been described in the literature so far. CASE PRESENTATION: We present an additional, fourth case of an AVM of the ureter, clinically presented as asymptomatic haematuria and an obstructive process in the left ureter. Ureteroscopic evaluation revealed a fibroepithelial polypoid-like lesion in the proximal ureter. After biopsy showed a benign lesion, the lesion was treated with the 2-µm continuous wave (cw) thulium laser. Histopathological examination revealed a polypoid laesion caused by a circumscribed arteriovenous malformation. Almost four years after operation the patient remains asymptomatic and free of recurrence. CONCLUSION: Arteriovenous malformations of the urinary tract are extremely rare. We presented a fourth case of a arteriovenous malformation of the ureter.