Extramedullary laryngeal plasmacytoma 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.

Infiltrative laryngeal disease in dogs

OBJECTIVES

To describe the clinical features and outcome of neoplastic and inflammatory infiltrative laryngeal disease in dogs.

MATERIALS AND METHODS

Medical records at a single referral centre were retrospectively reviewed for dogs diagnosed with infiltrative laryngeal disease by CT or laryngoscopy.

RESULTS

Fifteen dogs were included, with a median age of 6 years (range 1-14 years). Thirteen dogs were diagnosed with inflammatory disease including granulation tissue (n = 4) and neutrophilic (n = 2), septic neutrophilic (n = 2), eosinophilic (n = 1) lymphocytic/plasmacytic (n = 1) and mixed/unclassified (n = 3) inflammation. One dog was diagnosed with large cell lymphoma and one dog was diagnosed with mast cell tumour. Twelve dogs survived to discharge. Follow-up was available for 10 dogs diagnosed with inflammatory disease. Four had fully recovered (7, 10, 23 and 32 months) and one dog developed acute leukaemia and was euthanased at 2 months. Five dogs had recurrence of clinical signs at 1, 1, 5, 17 and 26 months. The dog with lymphoma was euthanased at 8 months and the dog with mast cell tumour died at 5 months.

CLINICAL SIGNIFICANCE

In this cohort, infiltrative inflammatory lesions of the larynx were more common than neoplastic infiltration. For dogs that survived to discharge, outcome was fair although relapse was common.

Spontaneous Regression of a Mandibular Plasmacytoma in a Juvenile Dog: A Case Report

A 4 mo old female Finnish lapphund presented for further investigation of a swelling of the right rostral mandible. A computed tomography scan showed the swelling to be an expansile and osteolytic mandibular lesion. Histopathology revealed a poorly differentiated, moderately well-demarcated, unencapsulated, highly infiltrative round cell neoplasm, and immunohistochemistry was supportive of a plasmacytoma. Performance of a rostral partial mandibulectomy was initially discussed with the owners, but the lesion improved spontaneously both clinically and on repeated computed tomography scanning before surgery could be performed. It subsequently almost completely resolved 6 mo after diagnosis. Hypotheses for spontaneous regression of the lesion are discussed and the human literature is briefly reviewed.

Extramedullary Pulmonary Plasmacytoma in a Dog

In this case report we are presenting a rare case of primary pulmonary plasmacytoma in a dog in the context of clinical and pathological findings. A six-years-old, female Rottweiler was brought to the clinic with respiratory complaints. The patient was dyspneic and tachypneic, and there were friction sounds on auscultation of the lungs. Laryngeal and tracheal palpation induced severe cough. Lateral and ventrodorsal radiographs of the thorax showed increased opacity in the lungs and loss of cardiac silhouette. Based on clinical and radiological findings, diagnosis of a lung mass was made and surgery recommended. Under general anesthesia, bilobectomy of the right lung lobes by medial sternotomy was performed. Upon cytological and histopathological findings, plasmacytoma was diagnosed.

Feline Respiratory Extramedullary Plasmacytoma with Lymph Node Metastasis and Intrahistiocytic Amyloid

A 14-year-old domestic longhaired cat presented with a 2-year history of nasal discharge and a recent onset of inappetence and submandibular lymphadenopathy. The cat was humanely destroyed after developing severe respiratory distress. Necropsy examination revealed thickened nasal turbinates and soft palate, and friable red–tan material within the frontal sinus, nasal cavity and nasopharynx. The lungs contained multifocal irregular friable tan nodules. Multiple lymph nodes were enlarged, friable and red–tan in colour. Histopathology revealed a mature type extramedullary plasmacytoma (EMP) within the frontal sinus, nasal cavity, soft palate, larynx, trachea, lungs and multiple lymph nodes. The lymph nodes and larynx also contained marked granulomatous inflammation with extensive intrahistiocytic (and lesser amounts of extracellular) lambda light chain amyloid, confirmed by electron microscopy and immunohistochemistry. Neoplastic cells expressed CD79a and MUM1. This is the first report of an infiltrative EMP of the feline respiratory tract with lymph node metastasis and predominantly intrahistiocytic amyloid.