Canine distemper causes demyelinating leucoencephalitis, like human multiple sclerosis. The encephalic microenvironment, including the extracellular matrix, is an important key factor of this lesion, already described in multiple sclerosis but not proved in canine distemper. Thereby, the aim of this work is to characterize the extracellular matrix in the encephalon of dogs with canine distemper. Samples of cortex and cerebellum of 14 naturally infected dogs with canine distemper virus were collected after being sent for necropsy in the Animal Pathology Laboratory of the Veterinary Hospital of Uberlândia Federal University. The samples were processed as routine, stained with Hematoxylin and Eosin (H.E), Masson Trichrome (MT), Periodic Acid-Schiff (PAS) and Reticulin, and then described. Areas of demyelination and necrosis were quantified in percentage of stain. The TM samples showed blue stain around vessels and meninge, which indicates a higher deposition of collagen in lesioned areas. At necrotic areas, reticulin stain pointed to a disorganization in the vascular wall and PAS-stained pink granules in macrophages. We conclude that the extracellular matrix seems to participate in the pathogeny of canine distemper. More research should be done to better detail the involvement of these molecules in the course of this disease.

Background: Secretory carcinoma is a rare mammary neoplasm observed in humans and animals. It was 1st called juvenile carcinoma. Secretory carcinoma is characterized by eosinophilic secretory material, both intra- and extracellularly, and neoplastic cells with a signet ring appearance. It is usually invasive, with a few rare reports of its non-invasive form, secretory carcinoma in situ, in humans. In veterinary medicine, only 2 cases of secretory carcinoma have been reported, both in dogs. This case is the 1st report of secretory carcinoma in a cat and the 1st instance of secretory carcinoma in situ in veterinary medicine, highlighting its histopathological, histochemical and immunohistochemical features. Case: A 15-year-old female mixed-breed cat was presented with multiple small nodules located in the right mammary chain. The cat underwent a mastectomy to remove the affected tissue. Upon histological examination of the cranial abdominal mammary gland (A1), a well-delimited neoplasm was identified. The tumor exhibited tubular and cluster formations of cells, with no evidence of invasion beyond the basal membrane. There was a significant deposition of both inter- and extracellular eosinophilic material, and the neoplastic cells showed prominent vacuolation, giving them a signet ring appearance. To further support the suspected diagnosis of secretory carcinoma, histochemical and immunohistochemical tests were conducted. Histochemical staining using Periodic Acid-Schiff (PAS), both with and without diastase digestion, revealed positive results for the neoplastic cells, indicating the presence of secretory material. Additionally, the cells tested positive for the alpha-lactalbumin antibody, further supporting the diagnosis of secretory carcinoma. The Ki67 proliferation index was measured at 30%, which is considered relatively high, indicating a notable degree of cell proliferation. Furthermore, immunohistochemical analysis confirmed the presence of myoepithelial cells surrounding the tubules and cell clusters, as demonstrated by the positivity for alpha-smooth muscle actin and p63. This confirmed the in situ nature of the neoplasm, as the absence of invasion was confirmed, leading to the definitive diagnosis of secretory carcinoma in situ. Unfortunately, no follow-up information was available regarding the cat's post-surgical condition. Discussion: The diagnosis of secretory mammary carcinoma in animals can be made based on the characteristic morphology, which includes the presence of both intra- and extracellular eosinophilic secretion and the vacuolated, signet ring appearance of the neoplastic cells. Histochemical and immunohistochemical techniques are essential to confirm the diagnosis. PAS staining, with and without the diastase reaction, is useful in identifying the secretory material within the cells. Furthermore, the positivity for alpha-lactalbumin in both the cytoplasm of the neoplastic cells and the extracellular secretion helps corroborate the diagnosis. It is important to differentiate secretory carcinoma in situ from other tumor types with a similar morphology, given the potential for aggressive behavior associated with this neoplasm. However, in the present case, the prognosis is likely more favorable due to the absence of invasion and metastasis, as evidenced by the in situ nature of the tumor. More cases of secretory carcinoma and secretory carcinoma in situ need to be diagnosed and described in veterinary medicine to gain a better understanding of their biological behavior and prognosis. Keywords: feline, alpha-lactalbumin, mammary neoplasm, PAS, secretion.

Mammary carcinomas in cats are highly aggressive neoplasms, often with the development of metastasis. Pleomorphic lobular carcinoma, on the other hand, is an invasive carcinoma with aggressive behavior, rarely diagnosed in humans and dogs. This report describes a case of pleomorphic lobular carcinoma in cats. The histopathological and immunohistochemical features of the neoplasm in this species were characterized. The neoplasm was diagnosed in a 10-year-old cat, with regional lymph node involvement at the time of diagnosis, but without systemic signs based on imaging tests performed prior to mastectomy. However, respiratory clinical signs developed approximately 40 days after surgery, accompanied by neoplastic pleural effusion, and the patient was euthanized due to the onset of neurological signs and poor prognosis. Although uncommon, pleomorphic lobular carcinoma is a neoplasm that can affect cats, and given its poor prognosis, it is important for oncologists and pathologists to be familiar with this entity. Carcinomas mamários em gatos são neoplasias altamente agressivas, frequentemente associadas ao desenvolvimento de metástases. O carcinoma lobular pleomórfico, por sua vez, é um carcinoma invasivo de comportamento agressivo, raramente diagnosticado em humanos e cães. Este relato descreve um caso de carcinoma lobular pleomórfico em um gato. As características histopatológicas e imuno-histoquímicas da neoplasia nesta espécie foram caracterizadas. A neoplasia foi diagnosticada em uma gata de 10 anos, com envolvimento de linfonodos regionais no momento do diagnóstico, mas sem sinais sistêmicos evidentes nos exames de imagem realizados antes da mastectomia. No entanto, sinais clínicos respiratórios surgiram cerca de 40 dias após a cirurgia, acompanhados de derrame pleural neoplásico, e a paciente foi eutanasiada devido ao início de sinais neurológicos e prognóstico reservado. Embora incomum, o carcinoma lobular pleomórfico é uma neoplasia que pode acometer gatos e, dado seu prognóstico desfavorável, é importante que oncologistas e patologistas estejam familiarizados com essa entidade.

Background: An epidermoid cyst is a result of the growth of epidermal elements in the dermis. It might occur anywhere in the body, both in humans and animals. A few case reports have demonstrated these cysts in the human mammary gland, but in the bitch mammary gland, it is not a reality. The exact pathogenesis of mammary epidermoid cysts remains unknown. At first, this lesion is considered benign; however, a malignant transformation can occur leading to squamous cell carcinoma. This paper reports the 1st occurrence of epidermoid cyst in the bitch mammary gland. Case: A mammary chain with the inguinal lymph node was received from a 12-year-old bitch mixed breed. Macroscopically, all glands had tumors, ranging from 0.7 cm to 3.5 cm along their longest axis. At the caudal thoracic gland (M2), a well-defined lump, measuring 2.0 x 1.8 x 1.4 cm, soft to firm consistency, with intact skin, was noted. After sectioning, a cystic cavity measuring 1.5 x 1.2 cm filled with a white-yellow caseous material, was observed. Samples were collected and submitted for routine histopathology. Microscopic analysis revealed tissue from the mammary gland covered by intact epithelium. Between the mammary glands, a large cystic cavity was observed, filled with lamellated keratin, acantholytic keratinocytes, neutrophils, foamy macrophages, and cellular debris. A thick layer of stratified squamous epithelium covered the cyst with some points of rupture infiltrated by neutrophils, macrophages, lymphocytes, and plasma cells, also with keratin released to the mammary stroma. The adjacent glands showed a few spots of ductal ectasia. Malignant criteria were absent. Discussion: Epidermoid cysts, commonly, arise from the infundibular portion of the hair follicle, are lined by squamous epithelium with a granular layer, and filled with laminated keratin. In humans, this entity might be found in the breast and could be a challenge to differentiate them from other benign and malignant conditions. As these lesions grow slowly through the accumulation of keratin over time, it can lead to complications by spontaneous rupture, release of no absorbable keratin that acts like an irritant material, stimulating secondary foreign body reactions, granulomatous reactions, or abscess formation. The inflammatory reaction results in local swelling and pain. The exact pathogenesis of mammary epidermoid cysts remains unknown; however, a few proposals exist: (a) congenital, arising from cell nests remaining from cells such as the embryonal mammary ridge; (b) obstruction of the hair follicle in the mammary dermis; (c) damage to the epidermis which gets implanted deep within the breast tissue and may occur in any type of trauma and/or previous procedures; (d) cystic ectasia of the infundibulum of hair follicles; and (e) squamous metaplasia of normal columnar cells within a dilated duct in fibroadenoma or fibrocystic change. The final diagnosis in this case was established by histopathological examination stained with hematoxylin and eosin. Epidermoid cyst is a benign lesion that occurs anywhere in the body, they are more common on the face, trunk, neck, extremities, scalp and has been described in the human mammary gland. In the authors’ assessment, this is the 1st description of epidermoid cyst in the bitch mammary gland. Although it is a very rare entity, pathologists need to be aware and should be considered as a differential diagnosis during mammary gland examination. Keywords: canine, squamous cells, epidermal inclusion, ductal metaplasia, laminated keratin, morphology.

An 8-year-old male rabbit (Oryctolagus cuniculus) presented with a subcutaneous mass in the proximal region of the fourth and accessory digit measuring 5.5 x 3.5 x 5.2cm. The mass was non-alopecic and exhibited irregular surface, ulceration and necrosis with predominantly pale and light brown coloring. Radiography revealed no involvement of bone and adjacent periosteum. The mass was marginally resected and the electrochemotherapy (ECT) was performed on the surgical bed. Histopathology and immunohistochemical analysis revealed positive reactions for Vimentin, Runx-2 and ki-67, leading to a diagnosis of extraskeletal osteosarcoma (ESOS). This report described a case of ESOS in a rabbit, thereby delineating its clinical presentation, anatomopathological characteristics, diagnostic modalities and recommended therapeutic interventions. Um coelho macho de 8 anos (Oryctolagus cuniculus) apresentava uma massa subcutânea na região proximal do quarto e acessório dígitos medindo 5,5 x 3,5 x 5,2 cm. A massa não era alopécica e exibia superfície irregular, ulceração e necrose com coloração predominantemente pálida e marrom clara. A radiografia não revelou envolvimento de tecido ósseo ou periósteo adjacente. A massa foi submetida à excisão marginal e foi realizada eletroquimioterapia do leito cirúrgico. Histopatologia e análise imunohistoquímica revelaram reações positivas para vimentina, Runx-2 e ki-67, levando ao diagnóstico de osteossarcoma extraesquelético. Este relato descreve um caso de osteossarcoma extraesquelético em um coelho, delineando sua apresentação clínica, características anatomopatológicas, modalidades diagnósticas e intervenções terapêuticas recomendadas.

The frequency of ovarian neoplasms in dogs is low, and these tumors are often underdiagnosed mainly due to nonspecific clinical signs. Multiple ovarian tumors are rarely described in dogs and can be of primary or secondary origin. Lymphomas, in turn, are among the most common malignant neoplasms in dogs, with a variable clinical course. This report describes a case of multiple concomitant ovarian tumors and a multicentric lymphoma in a dog, diagnosed histologically and confirmed by immunohistochemistry. The right and left ovaries and mesenteric lymph node of a 14-year-old mixed breed female dog were received for histopathological evaluation. Histologically, a multicentric small to intermediate cell lymphoma was diagnosed in the lymph node and both ovaries, in addition to a bilateral granulosa cell tumor and papillary adenocarcinoma in one of the ovaries. Immunohistochemistry determined the diagnosis of multicentric peripheral T-cell lymphoma. Coexisting ovarian tumors are rarely described in the literature but can occur. This is the first report of these three neoplasms occurring concomitantly in the same organ. Therefore, clinicians and pathologists should be aware of this possibility when evaluating ovaries.