Extramedullary plasmacytoma of the third eyelid gland in a dog

Melan-A immunolabeling in canine extramedullary plasmacytomas

Histologic diagnosis of less well-differentiated cases of canine extramedullary plasmacytomas (CEMPs) may require immunohistochemical confirmation to discriminate these tumors from other round cells tumors including lymphoma, cutaneous histiocytoma, and amelanotic melanomas. CEMPs are characterized by widespread immunoreactivity for multiple myeloma 1 (MUM1) antigen and λ light chains, while the melanocytic marker melan-A has been reported to yield negative results. Here, 33 randomly selected CEMPs, 20 melanocytomas, and 20 malignant melanomas were immunohistochemically tested for MUM1, melan-A, and PNL2. In addition, CEMPs were examined for PAX5, E-cadherin, CD3, CD18, CD20, S100, as well as λ and κ light chain immunoreactivity. All CEMPs were characterized by labeling for MUM1 and λ light chain, as well as variable immunopositivity for the remaining antibodies. Notably, 13 cases of CEMPs (39.4%) exhibited immunolabeling for melan-A. Melanocytic tumors immunolabeled for melan-A (40/40; 100%) and PNL2 (34/40; 85%). An unexpected cytoplasmic immunoreactivity for MUM1 was observed in 2 melanocytic tumors. Summarized, MUM1 or melan-A immunomarkers alone are not sufficient to differentiate between CEMPs and amelanotic melanomas and should be part of a larger immunopanel including λ light chain, CD20, and PNL2.

Primary third eyelid lymphoma with aggressive local behavior in a dog

Lymphoma is the most common hematopoietic neoplasm in dogs. However, cases primarily involving the third eyelid are rarely reported in the species. The subtype most frequently described in this location is marginal zone lymphoma of the mucosa-associated lymphoid tissue, which has an indolent behavior. A 10-year-old intact female Poodle was presented with a 2-month history of a nodule in the left third eyelid for evaluation. This nodule was surgically excised; however, local recurrence was detected nineteen days postoperatively, with the formation of a mass that expanded and replaced the extraocular orbital tissues and infiltrated the eye. Euthanasia was elected due to the deteriorating clinical condition, and a necropsy was performed. Macroscopically, the mass infiltrated and expanded the eyelids with narrowing of the palpebral fissure, expanded into the orbital space, and infiltrated the cornea and bulbar conjunctiva. Histologically, the mass was composed of sheets of intermediate to large neoplastic lymphocytes, with frequent epitheliotropism and tingible bodies. Neoplastic lymphocytes were immunoreactive for PAX5, CD20, and CD79a and were not immunoreactive for CD3. The neoplasm was restricted to the left eyelid and orbit. A diagnosis of primary third eyelid lymphoma (extranodal) with immunophenotype B and locally aggressive behavior was made based on the macroscopic, histological, and immunohistochemical findings.

Challenges in diagnosing canine spindle cell tumours using immunohistochemistry, illustrated by three nonpigmented malignant cases from the nictitating membrane

BACKGROUND

Nonpigmented malignant spindle cell tumours of the membrana nictitans are rare in dogs. In twenty-three years only three cases have been diagnosed in Scandinavia. This study describes the three cases of malignant tumours of the membrana nictitans recorded by the Eye Pathology Section, University of Copenhagen, Denmark, with reference to the clinical appearance and work-up, the treatment and prognosis, and the histopathological description including immunohistochemistry. The three cases are compared to previous publications on canine tumours of the nictitating membrane. We emphasize the importance of using protocols that are adapted to the specific species such as dogs. Opposite the human tissue responses, we even need more than one marker when diagnosing melanomas in dogs.

RESULTS

The dogs presented were an 8-year-old Dachshund, a 12-year-old Akita and a 14-year-old Shetland Sheepdog. All three dogs were entire females. All three nictitating membrane tumours developed on the right nictitating membrane as firm or multilobulated hyperaemic masses. Two of the tumours were macroscopically nonpigmented, the third being partly pigmented on the surface and ulcerated. According to the histopathology and for two of the cases immunohistochemistry with dog-adapted protocols the diagnoses included one hemangiosarcoma and two amelanotic melanomas. Tumour regrowth developed in all three cases and repeated resections were completed 1, 2 and 3 times, respectively, with recurrence experienced within 1.5 months - 3 years.

CONCLUSIONS

Nonpigmented malignant spindle cell tumours of the canine membrana nictitans are rare. Treatment of choice should be complete excision with a minimal histologic tumour-free distance and in case of a recurrence a full resection of the nictitating membrane. We strongly recommend a dog-adapted protocol for immunohistochemistry.

Conjunctival Extramedullary Plasmacytoma in Dogs and a Cat: Clinical Characteristics and Histopathological Findings

Simple Summary

Extramedullary plasmacytoma has been occasionally reported to affect the ocular and periocular (orbit, conjunctiva) region. To better describe the clinical and histopathological features of extramedullary plasmacytoma, we reviewed the records of seven cases (six dogs, one cat). In these cases, extramedullary plasmacytoma was found mostly in the conjunctiva of the third eyelid in the form of salmon-colored nodules with clear borders. All tumors were surgically removed with no additional therapy. No signs of recurrence or systemic involvement (multiple myeloma) were observed in the follow up period. We recommend that extramedullary plasmacytoma should be considered in cases of canine and feline conjunctival masses, followed by investigations to rule out multiple myeloma. Our results suggest that conjunctival extramedullary plasmacytoma is unlikely to recur or spread, and that local surgical excision alone or combined with cryotherapy should be curative.

Abstract

Background: Extramedullary plasmacytoma (EMP) is a plasma cell tumor that is very rarely reported in ocular and adnexal tissue and is usually solitary and benign. Methods: This study evaluated seven cases from different ophthalmology referrals submitted for histopathological analysis between 2013 and 2022. Results: EMPs were diagnosed in a 9-year-old domestic short-haired cat and in six dogs (median age, 10 years): three English Cocker Spaniels, a Golden Retriever, a Maltese, and a Pinscher. EMPs affected the third eyelid conjunctiva in five cases (5/7), followed by the superior bulbar (1/7) and palpebral conjunctivae (1/7), respectively, and were presented mostly as well-defined, salmon-colored nodules. Histopathologically, the masses were composed of sheets and packets of round cells morphologically consistent with mature plasma cells with mild anisocytosis and anisokaryosis; mitosis and binucleated giant cells were rarely observed. Follow up for 6/7 cases ranged from 6 months to 2 years. No signs of recurrence or systemic involvement (multiple myeloma) were observed. Conclusions: EMP should be included in the differential diagnoses of canine and feline conjunctival masses. Staging recommendations should include multiple myeloma diagnostic evaluation. Our results suggest that primary conjunctival EMP does not appear to be locally aggressive and has low systemic involvement behavior. The local surgical excision alone or combined with cryotherapy should be curative.

Unilateral mixed adenoma of the third eyelid lacrimal gland in a boxer dog

A female boxer dog was presented with a mass expanding the left third eyelid. Histopathology revealed a mass composed of pleomorphic cells arranged in tubuloacinar structures, a fibrovascular myxoid stroma, and intermixed trabeculae of woven bone. The mass was diagnosed as a mixed adenoma of the third eyelid lacrimal gland.

Parotid Salivary Gland Extramedullary Plasmacytoma with Local Lymph Node Metastasis in a Dog

A 12 yr old spayed female mixed-breed dog presented for evaluation of a recurrent soft-tissue sarcoma. On physical examination, a firm mass was palpated ventral to the left ramus of the mandible. A fine-needle aspirate of the mass was suggestive of a round-cell neoplasm. A complete blood count, serum biochemical profile, and an abdominal ultrasound with liver and splenic aspirates were performed, and no clinically relevant abnormalities were identified. Advanced imaging of the skull identified an enlarged parotid salivary gland and an enlarged ipsilateral medial retropharyngeal lymph node. The medial retropharyngeal lymph node was sampled via fine-needle aspiration, and a round-cell population similar to what was present in the mass was identified. An incisional biopsy was performed under general anesthesia, which yielded a diagnosis of salivary gland extramedullary plasmacytoma, confirmed with immunohistochemistry (MUM-1). The parotid salivary gland and medial retropharyngeal lymph node were then surgically excised, and metastasis to the lymph node was confirmed by histopathology. The dog remained alive for 685 days after surgery until she was euthanized for hindlimb paresis of undetermined cause.

Imaging diagnosis--FDG-PET/CT of a canine splenic plasma cell tumor

An 8-year-old Shih Tzu developed abdominal pain and hyperglobulinemia. A round splenic mass was noted radiographically and sonographically. The patient was evaluated by fluorodeoxyglucose positron emission tomography coupled with computed tomography (FDG-PET/CT). There was no evidence of metastasis or bone marrow involvement on PET/CT images. The standardized uptake value (SUV) of the splenic mass was increased over the reference range (SUV = 4.83). The patient was diagnosed as splenic extramedullary plasmacytoma through immunohistopathologic study. After the splenectomy, the globulin level normalized and the patient is alive without complications.

Penile extramedullary plasmacytoma in a dog

Penile tumours are rare in dogs. Reported herein is a case of a penile extramedullary plasmacytoma (EMP) in a 5-year-old male cocker spaniel that was brought to a local hospital for an evaluation of a penile mass. The mass was approximately 1.3 cm in diameter at the time of presentation. In fine needle aspiration and histopathological examinations, the neoplastic cells showed eccentric round nuclei, a moderate amount of basophilic cytoplasm, and a peri-nuclear clear zone, consistent with plasma cell morphology. There was nuclear pleomorphism with mononuclear giant cells and occasional bi-nucleation. Round cells on the periphery of the mass demonstrated plasmacytic differentiation. Immunohistochemically, the neoplastic cells stained positive for MUM1 and light lambda chain. Based on the cytological and pathological observations, a diagnosis of penile EMP was established.