ECP 2023 Abstracts

S169 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 Background & objectives: Diabetic mastopathy is a rare benign dis- ease of the breast (<1% of benign breast diseases) usually in premeno- pausal women with insulin-dependent diabetes mellitus mainly type I but also II. A differential diagnostic problem occurs between diabetic mastopathy and malignancy. Methods: A 34 and 37-year-old female patients with insulin- dependent DM, presented palpable lesions, both in left breast that were suspicious for malignancy. Patients underwent needle core biopsy. We examined the lesions microscopically and using immu- nohistochemistry. We reviewed electronic databases to identify and synthesize relevant published evidence to allow recommendations to be evidence-based wherever possible about the analysis of dia- betic mastopathy. Results: Macroscopically, lesions were whitish-coloured, ill defined, firm, scleroelastic tissue pieces. Microscopically, increased fibrosis keloidal type, periductal, perilobular and perivascular lymphocytic infiltrates and epithelioid stromal myofibroblasts were observed. Infarcts, liponecrosis, evidence of arteriitis or increased mitotic activ- ity were not identified. No evidence of malignancy was found. The histological picture was compatible with diabetic mastopathy. A dif- ferential diagnostic problem occurs between diabetic mastopathy and malignancy mainly on imaging control. Immunohistochemistry results: positive stains: CD10, SMA, desmin, CD34 and S100 CD20, and nega- tive stains: beta catenin, cytokeratins, p63 (useful in differential diag- nosis of invasive carcinoma) Conclusion: In conclusion, diabetic mastopathy is a rare inflammatory disorder of the breast, of unknown aetiology, (possible the result of an immune response to exogenous insulin administration, or hyper- glycaemia leads to stromal matrix expansion and accumulation of glycosylation end products and a B cell inflammatory response ), of benign nature, which can be differentiated from malignancy only by histological examination. E-PS-02-066 Tubular adenoma of the breast: a report on an uncommon case F. Sousa Vieira*, A.P. Rodrigues, D. Sá, S. Neves, G. Carrola, M.R. Correia, F.E. Costa, N.J. Lamas, J.R. Vizcaíno *Centro Hospitalar Universitário de Santo António, Portugal Background & objectives: Tubular adenomas of the breast are rare benign epithelial tumours that mostly occur in females of reproduc- tive age, rarely occurring before menarche or after menopause. These neoplasms are usually described as palpable, solitary, freely mobile, well-circumscribed masses, without associated pain. Methods: We report the case of a 13-year-old woman who had a lump in the upper inner quadrant of the left breast evolving for seven months. An ultrasound described a 57x29 mm hypoechoic homogeneous ovoid nodule. A needle biopsy was performed with a subsequently surgical excision of the lesion. Results: The histopathological examination revealed a well-circum- scribed proliferation of tubular structures of ductal type, mostly small and rounded, composed of a basal layer of myoepithelial cells and an inner layer of luminal cells, similarly to the normal mammary epi- thelium. There was no significant atypia, nor relevant mitotic activ- ity, nor necrosis. The lumen of the tubular structures contained a dense amorphous eosinophilic material (highlighted with PAS) and the surrounding stroma between the different tubular structures was fibrovascular and sparse. The luminal cells were immunoreactive for EMA and ER, while the myopepitelial layer was positive for p63 and SMA. The proliferative index (%Ki-67) was very low. Conclusion: Our patient is among the youngest ever individuals to be reported with the diagnosis of breast tubular adenoma, having symp- toms beginning as early as 12 years old. Unlike in this case, they tend to occur more frequently in the breast upper-outer quadrant. They can often be misdiagnosed because of their similar clinical appearance to other, more prevalent benign tumours, such as fibroadenomas. Tubular adenomas are benign lesions without associated increased malignancy risk and, thus, surgical excision grants complete resolution. E-PS-02-067 High-grade encapsulated papillary carcinoma (EPC) of the male breast: a rare case G. Stanc*, E. Souka, G. Galanopoulos, V. Tselepidis, H. Trihia, C. Valavanis *Pathology Department Metaxa Cancer Hospital, Greece Background & objectives: Encapsulated papillary carcinoma (EPC) is a rare, breast malignancy, with clinically indolent course. It is most common in postmenopausal women. EPC of the male breast is uncom- mon, and accounts for up to 7.5% of all male breast cancers. Methods: A 64-year-old male with no history of malignancy presented with a palpable cystic mass at the right breast, close to the nipple. A lumpectomy specimen 3X2, 5X1, 5cm in size was sent for gross and microscopic examination. A well circumscribed solid to cystic lesion, 1,5cm in great diameter was found. Total mastectomy and axillary sentinel lymph node excision were performed. Results: Microscopic examination revealed an encapsulated high grade papillary carcinoma. Peripherally to it an invasive micropapillary carci- noma 0,4cm in great diameter was found. The sentinel lymph node and the mastectomy margins were tumour free. Immunohistochemical examination revealed p63 (-) and CK14 (-) indi- cating the absence of myoepithelial cells at the periphery of the EPC. Both lesions displayed ER (+), PgR (+), Her-2 (-) and Ki-67 (+) in approximately 40% of the EPC neoplastic cells. Conclusion: EPCs are usually low and intermediate grade, staged and treated as in-situ disease. High grade EPCs have a low incidence (3% of EPC) and similar behav- iour to invasive carcinoma. Therefore, they are classified and staged as high-grade invasive breast carcinomas. In-situ and invasive disease may be focally present at the periphery of EPC and potentially unsampled at core-needle biopsy, therefore these lesions should be examined as a whole. E-PS-02-068 Assessment of intra-laboratory Ki67 reproducibility in breast can- cer using telemedicine platform I. Telezhnikova*, G. Setdikova, A. Abduraimov, S. Khomeriki, L. Zhukova *Loginov Moscow Clinical Research Center, Russia Background & objectives: Interlaboratory Ki67 reproducibility is still rather low. Difficulties are especially pronounced due to the lack of standardization of the visual calculations for Ki67. The aim of this study was to evaluate intra-laboratory Ki67 reproducibility in breast cancer. Methods: An experimental study was performed on biopsy material histological glass from 20 patients. The slides were scanned at 40x magnification by 3DHISTECH®. Slides were uploaded to the One- Cell telemedicine platform for pathology laboratories. For each slide, 4 fields of view 0.264 mm^2 were selected using markup tools. The mean deviation ± between pathologists and convergence coefficients by category were estimated. Results: The sample were 80 fields of view. Evaluation was performed by 3 pathologists. Categories Ki67 index were distinguished (1 - less than 20%, 2 – 20% to 35%, 3 - more than 35%). Ki67 categories were defined as 1 in 8 (40%) slides, 2 in 6 (30%), and 3 in 6 (30%). The mean deviation between pathologists on the convergence coefficient was 0.89 (0.87±0.93), with a median convergence of 90%. The total absolute deviation by category was 3.5 for pathologist markup 1, 7.75 for pathologist markup 2, and 4.5 for pathologist markup 3. The