Ultrastructure of feline mammary hypertrophy

Effectiveness of ovariohysterectomy on feline mammary fibroepithelial hyperplasia treatment

OBJECTIVES

The aim of this study was to evaluate the effectiveness of ovariohysterectomy (OVH) on feline mammary fibroepithelial hyperplasia (FMFH) treatment, as well as the influence of previous injectable progestin on clinical signs and treatment of FMFH.

METHODS

Seventy-nine female cats diagnosed with FMFH between 2014 and 2018 were included. The animals were distributed as follows: (1) treated only with OVH (TA) or OVH plus antiprogestin (TB); and (2) no administration (G1) or previous administration (G2) of injectable progestin before FMFH diagnosis. Data regarding clinical signs of FMFH, occurrence of persistent mammary growth after OVH, and time until complete remission of FMFH post-surgery were recorded and evaluated.

RESULTS

Mastectomy was not performed in any cat during the study. TA was adopted in 71/79 (89.9%) cases, with 42/71 (59.2%) from G2 and 29/71 (40.8%) from G1. TB was adopted in 8/79 (10.1%) cats, all from G2. Total remission of FMFH was observed in 73/79 (92.4%) cats, with six animals from G2 having died (n = 6/79 [7.6%]). The time until complete remission of FMFH was higher (P <0.0001) in cats from G2 than from G1. Moreover, animals from G2 had a higher percentage of persistent mammary growth after OVH (P <0.001) and a tendency to higher mortality (P = 0.052) compared with G1.

CONCLUSIONS AND RELEVANCE

Previous treatment with injectable progestin may result in a more complex clinical presentation of FMFH. Ovariohysterectomy is a good treatment option for FMFH when there is no interest in breeding the queen. Treatment with antiprogestin is recommended, especially if persistent mammary growth is detected after OVH.

Histological study of canine mammary gland during the oestrous cycle

The development of the mammary gland is a puzzling phenomenon and the research on this field has been focussed mostly on the carcinogenesis, with a less goal-oriented concern in basic histology. In order to determine the histological features of normal mammary gland in the different oestrous phases we used 39 non-pregnant female dogs of various breeds and ages. The animals were grouped in: pre-pubertal, pro-oestrous, oestrous, early and late dioestrous, early and late anoestrous phases. Major changes of the canine mammary histology throughout the oestrous cycle were identified in this study. A rudimentary gland with few ducts in the base of the nipple was observed in pre-pubertal female individuals and pubertal pro-oestrous female ones. In the oestrus, small inactive lobules associated with ductal branching and inconspicuous regressive changes were observed, while in early dioestrus, a ductal arborization was present. In late dioestrus, a complete lobuloalveolar differentiation and secretory capacity was achieved. The regressive histological features were abundant on early anoestrus, and markedly generalized on late anoestrus. The regressive process was longer in the more caudal gland pairs. This work provides baseline knowledge of canine mammary gland that may be relevant for interspecies comparative purposes and for pathologists dealing with mammary gland tumours.

Oestrogen and progesterone receptors in feline fibroadenomatous change: an immunohistochemical study

The distribution of oestrogen and progesterone receptors was analysed in 18 cases of feline fibroadenomatous change (FFAC) using commercially available specific monoclonal antibodies and the Avidin-biotin peroxidase complex technique on formalin-fixed, paraffin-embedded tissue. In all cases of FFAC, progesterone receptors were detected either in epithelial cells (mostly suprabasal) or in epithelial and stromal cells. Oestrogen receptors were detected in approximately half of these cases, in suprabasal or luminal epithelial cells exclusively. Myoepithelial cells lacked both oestrogen and progesterone receptors. The techniques used have identified the specific cellular distribution of steroid hormones receptors in this hormone-dependent lesion of the feline mammary gland. The results confirm those of previous biochemical analyses with respect to progesterone receptors and add new data concerning the possible involvement of oestrogen receptors and stromal fibroblasts in the hormonal control and development of the lesion.

Growth hormone mRNA in mammary gland tumors of dogs and cats

We have shown recently that in the dog progestin administration results in mammary production of immunoreactive growth hormone (GH). At present we demonstrate the expression of the gene encoding GH in the mammary gland of dogs and cats using reverse-transcriptase PCR. GH mRNA was found in the great majority of normal mammary tissues as well as benign and malignant mammary tumors of the dog and was associated with the presence of immunoreactive GH in cryostat sections. The mammary PCR product proved to be identical to that of the pituitary. The highest expression levels were found after prolonged treatment with progestins. In carcinomas GH mRNA was also found in progesterone receptor-negative tissue samples, indicating that after malignant transformation GH gene expression may become progestin independent. GH mRNA was also present in mammary tissues of cats with progestin-induced fibroadenomatous changes. It is concluded that GH gene expression occurs in normal, hyperplastic, and neoplastic mammary tissue of the dog. The expression in normal tissue is stimulated by progestins and might mediate the progestin-stimulated development of canine mammary tumors. The demonstration of progestin-stimulated GH expression in mammary tissue of cats indicates that the phenomenon is more generalized among mammals.

Disseminated malignant histiocytosis in a golden retriever: clinicopathologic, ultrastructural, and immunohistochemical findings

Diagnosis of malignant histiocytosis (MH), a disorder characterized by systemic proliferation of morphologically atypical histiocytes and their precursors, in an 8-year-old neutered female Golden Retriever was based on light and electron microscopic and immunohistochemical findings. Clinically, the dog presented with unilateral forelimb lameness. Eight days after surgical exploration of a swollen brachium, the dog developed sudden onset of posterior paresis, fecal and urinary incontinence, and a flaccid tail. Necropsy revealed infiltrative and nodular lesions in the right forelimb and regional lymph nodes, thoracic and abdominal cavities, and lumbar epidural space. Gross lesions were not found in the lungs or integument. Histopathologic examination showed infiltrates of atypical histiocytes in skeletal muscle, joint, and regional lymph nodes of the right forelimb; intercostal muscle; lung; liver; spleen; pancreas; kidneys; and spinal dura. Most tumor infiltrates were nodular and composed of loosely aggregated cells that were 10-30 microns in diameter with abundant eosinophilic to foamy cytoplasm, had central or eccentric nuclei, and were periodic acid-Schiff negative. Many binucleated cells, multinucleated giant cells, and mitotic figures were seen. Tumor cells contained phagocytosed erythrocytes, mononuclear cells, and some leukocytes. Ultrastructural features of tumor cells included cytoplasmic lipid droplets, lysosomes, and phagolysosomes. Immunohistochemical studies on paraffin-embedded sections showed positive reactivity to human T-cell Ag (clone UCHL-1) and for lysozyme, alpha-1-antitrypsin, and cathespin B. Polyclonal intracellular immunoglobulin reactivity and lectin binding (peanut, soybean, and wheat germ agglutinins and concanavalin A) were also demonstrated. Criteria for diagnosis of malignant histiocytic tumors and differential diagnosis are discussed.

Feline mammary sarcoma composed of cells resembling myofibroblasts

A recurrent mammary sarcoma from an 11-year-old, female domestic cat was studied by light and electron microscopy and immunohistochemistry. The tumor consisted of interlacing bands of spindle cells with elongated blunt-ended nuclei and variable amounts of stroma. Multinucleated tumor giant cells and mitoses were common. Ultrastructurally, tumor cells had abundant rough endoplasmic reticulum with dilated cisternae, a prominent Golgi complex, frequent mitochondria, bundles of intracytoplasmic filaments with focal densities, and discontinuous basal lamina-like material and cell junctions. These findings suggest that myofibroblast-like cells were the predominant type of tumor cell. Failure to demonstrate immunoreactivity for cytokeratins attested to the non-epithelial origin of these neoplastic cells. Uniform immunoreactivity with anti-vimentin antibodies and specific labelling of some tumor cells with antiserum to actin are compatible with an origin of this tumor from modified fibroblasts (i.e., myofibroblast-like cells). Tumors composed largely of myofibroblasts may be unique and warrant separate classification from other types of fibroblastic tumors in animals.