Spontaneously occurring intracranial lipomatous hamartoma in a young BALB/c mouse and a literature review

Smooth muscle hamartoma of the lungs in a Wistar Hannover rat

Hamartomas are tumor-like masses comprising disorganized normal tissue elements. To date, spontaneous hamartomas have been reported in several organs and tissues in rodents but not in the lungs. Here, we report the first case of a hamartoma in the lungs of a 108-week-old female Wistar Hannover rat. Grossly, a white spot, 7 mm in diameter, was observed on the costal surface of the left lung. Histopathologically, the nodular lesions adjacent to the bronchioles comprised mature smooth muscle cells. The lesion was not encapsulated and spread along the alveolar walls and ducts without compression of the surrounding tissue. In the nodules, elastic fibers enclosed small lumens lined with factor VIII-related antigen-positive endothelial cells. This structure suggested that the nodule mimicked an artery. Moreover, structural abnormalities were observed within the bronchioles and arterioles owing to the increased number of smooth muscle cells in the surrounding tissues. These features suggested that this was a case of tissue malformation rather than a neoplasm, leading to the diagnosis of a smooth muscle hamartoma of the lung.

Glioneuronal Hamartomas in the Central Nervous System of Two Goats

Two goats (6 months old and 5 years old) were evaluated for neurological signs including laboured breathing, stiffness and obtundation. Solitary masses were noted in the brainstem and spinal cord, respectively. Histopathology of both cases revealed the lesions were composed of a mixture of glial and neuronal cells, consistent with glioneuronal hamartomas. The cause of death was attributed to the mass in the 6-month-old, while the cause of death in the 5-year-old was attributed to listeriosis. Hamartomas of neural origin are rarely described in veterinary species, and this report represents the first report of glioneuronal hamartomas in goats.

Bilateral hamartomatous medullary lipoma within the nasal turbinate bones in a cynomolgus monkey (Macaca fascicularis)

A 15-year-old male cynomolgus monkey (Macaca fascicularis) showed large bilateral masses in the maxillary sinus. In histopathological examination, both masses revealed benign medullary lipomas within the turbinate bones. The tumors were composed of well-developed lipocytes, trabecular bones and a few blood vessels. Although we initially diagnosed the tumor as bilateral lipomas in the nasal turbinates, it was not differentiated from lipomatous hamartoma. Findings, such as unique symmetrical proliferation, lack of border from the normal marrow and the intact surrounding tissue, indicated a lipomatous hamartoma/hamartomatous lipoma, thought to be a suitable diagnosis of the lesion. Of most interest was that such a proliferating lesion occurred in the nasal turbinate.

An unusual lipomatous brain mass in a Golden Retriever dog

A 9-year-old Golden Retriever dog was presented to the Veterinary Medical Center with a 3-week history of grand mal seizures and was subsequently euthanized. At autopsy, a discrete, firm, expansile mass was found in the right pyriform lobe, which compressed the ipsilateral hippocampus, thalamus, and cerebral cortex. Histologically, the mass was composed of well-differentiated adipose tissue supported by fibrous and mucinous stroma. Adipocytes exhibited strong immunoreactivity for vimentin and were negative for pancytokeratin (AE1/AE3), glial fibrillary acidic protein, neuron-specific enolase, and synaptophysin. These findings are most compatible with an intracranial lipomatous hamartoma, which is an extraparenchymal lesion that has been identified in several species. The current report describes an intracerebral lipomatous hamartoma in a veterinary species.

Histopathological and immunohistochemical characterization of spontaneously occurring uterine deciduomas in young adult rats

Uterine deciduomas were found in two female virgin rats, a 15-week-old Lewis rat and a 7-week-old Sprague-Dawley rat. The firm white nodules were located at the base of unilateral uterine horns and were approximately 6 mm and 4 mm in diameter. Histopathologically, the nodules were composed of three areas, each with a distinct type of proliferating cells: large epithelioid decidual cells with round nuclei, prominent nucleoli and abundant eosinophilic cytoplasm (antimesometrial region); compact spindle-shaped cells with oval nuclei and vacuolar cytoplasm (transitional region); and pleomorphic and spiny cells with round to oval nuclei and compact eosinophilic cytoplasm (mesometrial region). These cells proliferated in sheet-like arrangements and transformed into the other types of cells located in surrounding regions. Immunohistochemically, proliferating cells in all regions were strongly positive for proliferating cell nuclear antigen. The proliferating cells were positive for vimentin, and large decidual cells were positive for common acute lymphoblastic leukemia antigen 10, a marker of uterine interstitial cells. Large decidual cells were positive for α-smooth muscle actin and desmin, suggesting differentiation into muscular cells. Progesterone receptor was expressed in all cell types; however, estrogen receptor α was not expressed in the antimesometrial region. These extremely rare tumor-like nodules represent nonneoplastic lesions referred as decidual reactions of endometrial interstitial cells, and their biological behavior is that of a space-occupying benign tumor in young rats. Our cases might provide information as a historical control in toxicity and pharmacological studies in rats.