ORF virus causes tumor-promoting inflammation in sheep and goats.

ORF virus (ORFV) causes contagious ecthyma ("ORF"), a disease of sheep and goats characterized by lesions ranging from vesicles and pustules to atypical papilloma-like and angiomatous lesions in the skin and mucosae. The authors investigated the molecular factors leading to the ORF-associated atypical tumor-like changes. Fifteen lambs, 15 kids, and an adult ram clinically affected by natural ORFV infection were enrolled in the study and examined by several methods. ORFV was detected by viral culture or real-time polymerase chain reaction (RT-PCR) in the lesioned tissues and in the blood of the clinically affected sheep and goats. Surprisingly, ORFV was also detected in the blood of healthy goats from an affected herd. Microscopically, they found a pseudo-papillomatous proliferation of the epithelium, while the dermis and lamina propria were expanded by a proliferating neovascular component that highly expressed the viral vascular endothelial growth factor (vVEGF) and its host receptor vascular endothelial growth factor receptor 2 (VEGFR2). Immunohistochemistry, immunofluorescence, and in situ hybridization for mRNA showed that epidermal growth factor receptor (EGFR) was expressed in the fibrovascular component, in the infiltrating CD163+ macrophages, and in the basal stratum of the epidermis. Confocal immunofluorescence microscopy demonstrated that CD163+ macrophages were associated with VEGF and VEGFR2. Finally, they found by quantitative RT-PCR the overexpression of the interleukin-6 and VEGFR2 genes in the lesioned tissues. These findings suggest that ORFV activates an inflammatory reaction characterized by CD163+ macrophages expressing EGFR and VEGFR2, which might play an oncogenic role through synergistic action with vVEGF signaling.

A rare case of radiation-induced breast angiosarcoma: a case report.

We describe a rare case of a 77-year-old woman with radiation-induced breast angiosarcoma (RIAS) in whom radical surgery with negative margins determined that at 14-month of follow-up there is no evidence of either local or systemic recurrence without having to resort to adjuvant chemotherapy.

Primary Ewing sarcoma of the lung: A systematic review of the recent literature.

Primary pulmonary Ewing sarcoma (PES) is a rare malignancy with only sporadic cases reported in the scientific literature. We performed a systematic review of the cases published in the last decade on PubMed, with the aim to describe the clinical, pathological, therapeutic, and prognostic data of PES. Forty-two articles reporting on 50 cases have been reviewed. Globally, 60 % of the patients were males, and the mean age at diagnosis was 30.5 years, with only a few cases diagnosed after 50 years of age. The most common clinical manifestations at diagnosis were dyspnea, cough and chest pain. The most common immunohistochemistry findings were staining for CD99 and (less frequently) for vimentin, and no staining for TTF-1, cytokeratin, desmin and S-100. ESWR1-FL1 translocation was tested in less than half of the cases. The disease was often locally advanced, treated generally with multidisciplinary treatment combining surgery, chemotherapy and radiation therapy. Among patients with follow-up data, approximately 40 % were dead at the time of publication, with the median survival being 11.5 months. Among those who were alive, only 8.3 % was free from disease at 48 months from diagnosis.

Molecular Insights into the Genetic Variability of ORF Virus in a Mediterranean Region (Sardinia, Italy).

Orf virus (ORFV) represents the causative agent of contagious ecthyma, clinically characterized by mild papular and pustular to severe proliferative lesions, mainly occurring in sheep and goats. In order to provide hints on the evolutionary history of this virus, we carried out a study aimed to assess the genetic variation of ORFV in Sardinia that hosts a large affected small ruminant population. We also found a high worldwide mutational viral evolutionary rate, which resulted, in turn, higher than the rate we detected for the strains isolated in Sardinia. In addition, a well-supported genetic divergence was found between the viral strains isolated from sheep and those from goats, but no relevant connection was evidenced between the severity of lesions produced by ORFV and specific polymorphic patterns in the two species of hosts. Such a finding suggests that ORFV infection-related lesions are not necessarily linked to the expression of one of the three genes here analyzed and could rather be the effect of the expression of other genes or rather represents a multifactorial character.

Cystic Echinococcosis: Clinical, Immunological, and Biomolecular Evaluation of Patients from Sardinia (Italy).

Cystic echinococcosis (CE), a zoonotic disease caused by the larval stage of the tapeworm Echinococcus granulosus sensu lato (s.l.), is a worldwide public health problem. Echinococcus granulosus sensu stricto (s.s.), associated with G1 and G3 genotypes, is endemic with high prevalence in the Mediterranean basin. The parasite's life cycle comprises definitive hosts (canids) and intermediate hosts (ruminants) and can occasionally involve humans. The main aim of this research was to confirm the diagnosis of 13 patients suspected of CE who presented different complications and needed the surgical removal of the cysts. We also wanted to understand and clarify more the diagnosis of echinococcosis in humans. For this purpose, the patients first underwent cyst evaluation by ultrasound (US), immunological analysis, and then total pericystectomy, followed by parasitological, histopathological, and molecular biology examinations of the cysts. US stadiated one CE1, one CE2, eight CE3b, one CE4, and two CE5; immunology evidenced nine positives; histopathology confirmed 11 CE cysts, of which 8 fertile presenting protoscoleces were identified as E. granulosus s.s. by molecular biology, genotyped as three G1 and four G3 by neighbor-joining (NJ) phylogenetic tree. In conclusion, the results showed that 11 patients were affected by E. granulosus s.s. G1 orG3, and 2 cystic neoformations were of non-parasitic origin.

Histological and Immunohistochemical Features of Trichoblastoma in a Sarda Breed Sheep.

Skin tumors with adnexal differentiation are commonly reported in dogs and cats, while only anecdotal evidence is available in sheep. Here we illustrate the macroscopic, histologic, and immunohistochemical features of a cutaneous lesion with adnexal differentiation in a 6-year-old female Sarda breed sheep, surgically treated for a horn-like mass located in the left pinna. Additionally, we investigate a possible contribution of Ovine Papillomaviruses (OaPVs). Histologically, the dermis was expanded by an expansive and unencapsulated multilobulated nodule composed of cuboidal to spindle basaloid cells arranged in variably-sized cytokeratins (CK) AE1-AE3, CK 5/6 and CK 34 beta E12, p63-positive winding cords with a characteristic palisade arrangement of neoplastic cells in the periphery of the tumor. Based on these results, the cutaneous neoplasm was diagnosed as a trabecular trichoblastoma with spindle cells and rare structures resembling papillary mesenchymal bodies. Additionally, multiple enlarged sebaceous lobules clustered around dilated ducts suggestive of sebaceous gland hyperplasia were detected near the trichoblastoma. No PV DNA was found in the examined tissues, suggesting that ovine PVs are not involved in the pathogenesis of the present skin tumors with adnexal differentiation. Further investigations and efforts are required to elucidate the prevalence of skin tumors with adnexal differentiation in this species.

Italian observational study on HPV infection, E6, and p16 expression in men with penile cancer.

BACKGROUND: Human Papillomavirus (HPV) infection is one of the most important causes of cancer. It can play a role in cervical and extra-cervical cancers. Penile cancer is rare, even if an increasing trend was recently reported. Aim of the present study was to assess the prevalence and distribution of HPV genotypes in cases of penile cancer diagnosed in Sardinia, Italy. Surrogate markers of HPV infection (i.e., E6 and p16 genes) were also evaluated in all cases. METHODS: An observational, retrospective study which recruited all cases of penile cancer diagnosed between 2002 and 2019 at a tertiary care hospital in Sardinia, Italy, was carried out. HPV-DNA detection and genotyping were performed by Real-time PCR. Specimens were tested for oncogene E6 mRNA and for p16(INK4a) expression. RESULTS: HPV prevalence was 28.1% (9/32); HPV-16 was the most prevalent genotype (7/9, 77.8%). p16INK4a positivity was found in 66.7% of the samples with a statistically significant difference between HPV-positive and -negative groups. E6-transcript was detected in 71% of the HPV-16 positive samples. The overall survival was not statistically different between HPV-positives and -negatives. DISCUSSION: The present study confirms the etiologic role of HPV in penile cancer and supports the adoption of vaccination strategies in men and women. Further studies should clarify the diagnostic and prognostic role of E6 and p16 proteins. CONCLUSION: HPV infection can favor the occurrence of penile cancer, whose diagnosis and prognosis could be improved with the implementation of validated molecular techniques.

Distribution of HPV Genotypes in Patients with a Diagnosis of Anal Cancer in an Italian Region.

Objectives: Anal cancer is a rare disease. However, its incidence is increasing in some population groups. Infection caused by Human Papillomavirus (HPV) is strongly associated with the risk of anal cancer, whose variability depends on samples, histology, and HPV detection methods. The aim of the study was to assess prevalence and distribution of HPV genotypes in patients diagnosed with anal carcinoma. Methods: An observational, retrospective study was carried out in a tertiary care hospital in North Sardinia, Italy. Specimens of anal cancer diagnosed from 2002-2018 were selected. Demographic, epidemiological, and clinical variables were collected to assess their relationship with the occurrence of anal cancer. Results: The overall HPV positivity was 70.0% (21/30), with HPV-16 being the predominant genotype (~85%). The highest prevalence of anal cancer was in patients aged ≥55 years. HPV positivity was higher in women (p-value > 0.05) and in moderately differentiated samples (G2) (p-value < 0.05). p16INK4a and E6-transcript positivity were found in 57% and 24% of the HPV positive samples, respectively. The OS (overall survival) showed a not statistically significant difference in prognosis between HPV positive sand negatives (10, 47.6%, vs. 4, 44.4%; p-value = 0.25). Conclusions: HPV-DNA and p16INK4a positivity confirmed the role of HPV in anal carcinoma. Our findings could support the implementation and scale-up of HPV vaccination in males and females to decrease the incidence of HPV-associated cancers. Further studies are needed to better clarify the prognostic role of HPV/p16 status.

Histologic subtyping affecting outcome of triple negative breast cancer: a large Sardinian population-based analysis.

BACKGROUND: Triple Negative breast cancer (TNBC) includes a heterogeneous group of tumors with different clinico-pathological features, molecular alterations and treatment responsivity. Our aim was to evaluate the clinico-pathological heterogeneity and prognostic significance of TNBC histologic variants, comparing "special types" to high-grade invasive breast carcinomas of no special type (IBC-NST). METHODS: This study was performed on data obtained from TNBC Database, including pathological features and clinical records of 1009 TNBCs patients diagnosed between 1994 and 2015 in the four most important Oncology Units located in different hospitals in Sardinia, Italy. Kaplan-Meier analysis, log-rank test and multivariate Cox proportional-hazards regression were applied for overall survival (OS) and disease free survival (DFS) according to TNBC histologic types. RESULTS: TNBC "special types" showed significant differences for several clinico-pathological features when compared to IBC-NST. We observed that in apocrine carcinomas as tumor size increased, the number of metastatic lymph nodes manifestly increased. Adenoid cystic carcinoma showed the smallest tumor size relative to IBC-NST. At five-year follow-up, OS was 92.1, 100.0, and 94.5% for patients with apocrine, adenoid cystic and medullary carcinoma, respectively; patients with lobular and metaplastic carcinoma showed the worst OS, with 79.7 and 84.3%, respectively. At ten-years, patients with adenoid cystic (100.0%) and medullary (94.5%) carcinoma showed a favourable prognosis, whereas patients with lobular carcinoma showed the worst prognosis (73.8%). TNBC medullary type was an independent prognostic factor for DFS compared to IBC-NST. CONCLUSIONS: Our study confirms that an accurate and reliable histopathologic definition of TNBC subtypes has a significant clinical utility and is effective in the therapeutic decision-making process, with the aim to develop innovative and personalized treatments.

Clinical and pathological factors influencing survival in a large cohort of triple-negative breast cancer patients.

BACKGROUND: To provide further information on the clinical and pathological prognostic factors in triple-negative breast cancer (TNBC), for which limited and inconsistent data are available. METHODS: Pathological characteristics and clinical records of 841 TNBCs diagnosed between 1994 and 2015 in four major oncologic centers from Sardinia, Italy, were reviewed. Multivariate hazard ratios (HRs) for mortality and recurrence according to various clinicopathological factors were estimated using Cox proportional hazards models. RESULTS: After a mean follow-up of 4.3 years, 275 (33.3%) TNBC patients had a progression of the disease and 170 (20.2%) died. After allowance for study center, age at diagnosis, and various clinicopathological factors, all components of the TNM staging system were identified as significant independent prognostic factors for TNBC mortality. The HRs were 3.13, 9.65, and 29.0, for stage II, III and IV, respectively, vs stage I. Necrosis and Ki-67 > 16% were also associated with increased mortality (HR: 1.61 and 1.99, respectively). Patients with tumor histotypes other than ductal invasive/lobular carcinomas had a more favorable prognosis (HR: 0.40 vs ductal invasive carcinoma). No significant associations with mortality were found for histologic grade, tumor infiltrating lymphocytes, and lymphovascular invasion. Among lymph node positive TNBCs, lymph node ratio appeared to be a stronger predictor of mortality than pathological lymph nodes stage (HR: 0.80 for pN3 vs pN1, and 3.05 for >0.65 vs <0.21 lymph node ratio), respectively. Consistent results were observed for cancer recurrence, except for Ki-67 and necrosis that were not found to be significant predictors for recurrence. CONCLUSIONS: This uniquely large study of TNBC patients provides further evidence that, besides tumor stage at diagnosis, lymph node ratio among lymph node positive tumors is an additional relevant predictor of survival and tumor recurrence, while Ki-67 seems to be predictive of mortality, but not of recurrence.

Primary breast chondrosarcoma: Imaging and pathological findings.

We present the case of a 62 year-old woman who was admitted to our institute of radiological sciences for a breast mass developed in the last few months. The final diagnosis was primary breast chondrosarcoma and the surgical treatment performed, based on imaging and pathological findings, was the mastectomy.

Tracheobronchopathia Osteochondroplastica: a rare case report of a non-smoker and non-atopic patient, with a long history of wheezing since childhood.

BACKGROUND: Tracheobronchopathia Osteochondroplastica (TBPO) is an uncommon and benign condition characterized by osseous or metaplastic cartilaginous 1-3 mm nodules in the submucosa of the tracheo-bronchial tree. Posterior membranous wall of trachea is typically spared. Ecchondrosis and exostosis nodules can cause chronic inflammation and mucosal metaplasia, stiffness and airway obstruction. The prevalence of this disease, often asymptomatic or associated with nonspecific symptoms, is underestimated, and the mean age at diagnosis is 50 years. CASE PRESENTATION: We report a case of a 49 year old male, non-smoker. He was a smith, homeless, born in Romania and reported a diagnosis of asthma since childhood. He was admitted to our Respiratory Unit presenting low-grade fever with profuse sweating, cough, purulent sputum, and ground-glass opacity with irregularity in main bronchi detected by High-Resolution Computed Tomography (HRCT) scan. Fibrobronchoscopy revealed the presence of mucosal irregularities up to the segmental bronchi entrance. Histological examination showed nodules of osseouscartilaginous nature, consistent with TBPO. Microbiological tests of Bronchoalveolar Lavage fluid also revealed an infection by Pseudomonas Aeruginosa. CONCLUSION: TBPO is a rare disease characterized by wheezing, cough, hemoptysis, and recurrent pulmonary infections, with typical onset during adulthood. In the case reported, the symptoms began in childhood, although they had been misinterpreted as asthma. Even if childhood-onset is not reported in literature, it is likely that small changes occur in the first few years of life and become more evident in adulthood. The involvement of segmental and sub-segmental bronchi, usually spared in TBPO, could explain the presence of wheezing and non-productive cough reported by our patient since childhood.

Usefulness of magnetic resonance in patients with invasive cancer eligible for breast conservation: a comparative study.

BACKGROUND: The role of magnetic resonance imaging (MRI) in newly detected breast cancer remains controversial. We investigated the impact of preoperative MRI on surgical management of infiltrating breast carcinoma (IBC). METHODS: We reviewed data of 237 patients with IBC who were suitable for breast-conserving surgery (BCS) between 2009 and 2011. Of these patients, 109 underwent preoperative MRI (46%; MRI group) and 128 did not (54%; no-MRI group). We analyzed MRI-triggered changes in surgical plan and compared differences in rates of positive margins and mastectomy. RESULTS: Tumor size was larger in the MRI group (16.8 mm vs. 13.9 mm; P < .001). MRI changed the initial surgical planning in 18 of 109 patients (16.5%) because of detection of larger tumor diameter requiring wider resection (8 patients [7.3%]) or additional malignant lesions in the ipsilateral (9 patients [8.2%]) or contralateral breast (1 patient [0.9%]). MRI-triggered treatment changes included mastectomy (n = 12), wider excision (n = 5), and contralateral BCS (n = 1). Reoperation rates for positive margins after BCS appeared higher in the no-MRI group (4.1% vs. 8.6%), but the difference missed statistical significance (P = .9). Overall mastectomy rates were higher in the MRI group (13.7% vs. 7.0%; P < .05). The likelihood of having a change of treatment resulting from MRI was significantly higher for patients with tumors > 15 mm and for those with positive lymph nodes. CONCLUSION: Lymph node positivity and tumor size > 15 mm may predict an MRI-triggered change in surgical plan. Preoperative MRI resulted in higher mastectomy rates justified by biopsy-proven additional foci of carcinoma and did not significantly reduce reoperation rates for positive margins.

High HPV-51 prevalence in invasive cervical cancers: results of a pre-immunization survey in North Sardinia, Italy.

BACKGROUND: Human Papilloma virus (HPV) is recognized as the etiological agent of benign and malignant ano-genital lesions. The most prevalent genotypes associated with cervical carcinoma are HPV-16 and -18 worldwide. However, recent studies have emphasized the role of other genotypes, such as HPV-51, in the pathogenesis of cervical dysplasia. The aim of the study was to estimate the burden of HPV-51 infection in invasive cervical malignant lesions in Northern Sardinia, Italy. METHODS/PRINCIPAL FINDINGS: An observational, retrospective, prevalence, mono-center study was carried out to evaluate the presence of HPV genotypes in tissues biopsies of cervical lesions (CIN-1, CIN-2, CIN-3 and invasive carcinoma) gathered from 1996 to 2009. Biological samples were collected from women admitted consecutively to a tertiary university hospital situated in Sassari, Italy. Molecular methods were used to identify 28 oncogenic HPV types. A total of 155 formalin-fixed and paraffin-embedded cervical tissue samples were analyzed. Approximately half of the cervical lesions were classified as invasive carcinoma. HPV-DNA was detected in 71% of the samples, with a higher frequency (100%) in those categorized as invasive neoplasia. Mono- or co-infections were demonstrated in 45.8% and 25.8% of the cervical samples, respectively. Overall, the most prevalent HPV types were -16 (49%) and -51 (19.4%), with an increased frequency of detection associated with the severity of the cervical lesions. CONCLUSIONS/SIGNIFICANCE: This survey highlights for the first time the relevant role of HPV-51 infection in the pathogenesis of invasive cervical cancer prior to the introduction of a vaccination program. Although a selection bias could have influenced the results, other recent studies have described the impact of HPV-51. This remarkable epidemiological element should be carefully evaluated, particularly in the view of opting for preventive vaccines, whose cross-protection patterns determine their efficacy in protecting against infection from HPV types that are not included in the vaccine itself.

Chest tuberculosis with mediastinal asymptomatic lymphadenitis without lung involvement in an immunocompetent patient.

Tuberculosis remains the major cause of morbidity and mortality by a single infectious agent, particularly in developing countries. In recent years, we have witnessed the emergence of uncommon radiographic patterns of chest tuberculosis. Lymphadenitis is the most common extrapulmonary tuberculosis (TB) manifestation which, in developed countries, occurs more frequently in childhood, but also among adult immigrants from endemic countries and in HIV-infected people. Isolated and asymptomatic mediastinal lymphadenitis is uncommon in immunocompetent adults. We report a case of a young adult man from Senegal affected by sovraclavear and mediastinal TB lymphadenitis, which contains some uncommon elements: no compromised immunity, especially no HIV-infection, no lung lesions, no symptoms of infection or of mediastinum involvement, and rapid response to therapy in terms of mass size reduction. Examination of extra-thoracic lymph nodes and the patient's characteristics guided our diagnostic process to suspect TB. Surgical biopsy and subsequent histopathological and microbiological examinations of lymph material, first by Lowestein-Jensen and BACTEC cultures that remain the gold standard of diagnosis, confirmed the diagnosis. Chest X-ray was inconclusive; however, CT played an important role in the diagnostic course and in the management of the patient, particularly in determining disease activity, offering mediastinum and parenchymal details, as well as in identifying typical features of tuberculous lymph nodes and also of active/non active disease. Six months of antimycobacterial regimen is the recommended treatment in TB lymphadenitis of HIV-negative adults.

Prevalence and type distribution of human papillomavirus infection in women from North Sardinia, Italy.

BACKGROUND: Human papillomavirus (HPV) has been associated with several disorders of the genital tract, skin and oropharynx. The aims of our study were to evaluate the prevalence of HPV infection in women between 15 and 54 years of age in North Sardinia, Italy, to identify the prevalence of High Risk - Human papillomaviruses (HR-HPV) genotypes and to establish a correlation between molecular and cytological results. METHODS: From 2007 to 2009 we consecutively enrolled women aged 15-54 years admitted to public and private outpatient settings. All the participants filled in a questionnaire about the socio-cultural state, sexual activity and awareness about HPV. 323 cervical specimens were tested for HPV-DNA and HPV genotypes with INNO-LiPA HPV Genotyping CE Amp kit. Samples showing positivity to some HPV genotypes were re-tested using "in house" quantitative Real-Time PCR assays. RESULTS: Overall HPV-DNA positivity was detected in 35.9% of the women. The prevalence of HR-HPV infection among HPV positive samples was 93.1% with a specific prevalence of HPV 16, 51, 31, 53 and 18 of 54.3%, 37.9%, 10.3%, 6.9% and 5.2%, respectively. Co-infection with any HPV, HR-HPV, LR-HPV and HR/LR-HPV type was 18.3%, 14.9%, 0.9% and 2.5%, respectively; HPV 16/51 co-infection was detected in 64.6% of the HR-HPV co-infection group. The most frequent HPV-genotypes detected were 16 (32.5%) and 51 (22.7%). Among the 57 patients harboring mono-infection the most prevalent HPV genotypes were 16 (38.6%) and 31(10.5%). A multivariate analysis identified a statistical significant association between HPV infection and age and between HPV infection and previous sexual transmitted diseases. A statistically significant association between cytological cervical lesions and generic HPV exposure was identified. CONCLUSIONS: To our knowledge, this is the first survey evaluating the prevalence of HPV infection in Northern Sardinia and drawing attention to the unusual high proportion of genotype HPV 51. Given the recent implementation of a widespread immunization program with vaccines not containing HPV 51, it has been relevant to prove the high prevalence of this HPV genotype from the start of the vaccination campaign, in order to avoid in the future attributing to the vaccination program a possible selection effect (HPV replacement).

Spontaneous feline mammary intraepithelial lesions as a model for human estrogen receptor- and progesterone receptor-negative breast lesions.

BACKGROUND: Breast cancer is the most frequently diagnosed cancer in women. Intraepithelial lesions (IELs), such as usual ductal hyperplasia (UH), atypical ductal hyperplasia (ADH), and ductal carcinoma in situ (DCIS) are risk factors that predict a woman's chance of developing invasive breast cancer. Therefore, a comparative study that establishes an animal model of pre-invasive lesions is needed for the development of preventative measures and effective treatment for both mammary IELs and tumors. The purpose of this study was to characterize the histologic and molecular features of feline mammary IELs and compare them with those in women. METHODS: Formalin-fixed, paraffin-embedded specimens (n = 205) from 203 female cats with clinical mammary disease were retrieved from the archives of the Purdue University Animal Disease Diagnostic Laboratory and Veterinary Teaching Hospital (West Lafayette, IN), and the Department of Pathology and Veterinary Clinic, School of Veterinary Medicine (Sassari, Italy). Histologic sections, stained with hematoxylin and eosin (HE), were evaluated for the presence of IELs in tissue adjacent to excised mammary tumors. Lesions were compared to those of humans. Immunohistochemistry for estrogen receptor (ER-alpha), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER-2/neu) and Ki-67 was performed in IELs and adjacent tumor tissues. RESULTS: Intraepithelial lesions were found in 57 of 203 (28%) feline mammary specimens and were categorized as UH (27%), ADH (29%), and DCIS (44%). Most IELs with atypia (ADH and DCIS) were associated with mammary cancer (91%), whereas UH was associated with benign lesions in 53% of cases. Feline IELs were remarkably similar to human IELs. No ER or PR immunoreactivity was detected in intermediate-grade or high-grade DCIS or their associated malignant tumors. HER-2 protein overexpression was found in 27% of IELs. CONCLUSION: The remarkable similarity of feline mammary IELs to those of humans, with the tendency to lose hormone receptor expression in atypical IELs, supports the cat as a possible model to study ER- and PR-negative breast lesions.