Immunohistochemical evaluation of the effects of paraffin section storage on biomarker stability

Environmental stresses can alter immunoreactivity of biomarkers in stored tissue sections. The effect of temperature and lighting on 49 cellular or microbial antigens was evaluated in 4 serial paraffin sections, cut 12 months, 10 months, 8 months, 5 months, 3 months, 1 month, 3 days, and 1 day before immunohistochemistry. Slides were stored at room temperature (RT) in the dark, at 4°C in the dark, at RT under fluorescent light, or at RT with windowpane exposure to sunlight. Immunohistochemistry was performed simultaneously in an automated immunostainer. Immunoreactivity was compared with that in the corresponding 1-day-old section and scored as 4 (<10% reduction), 3 (10%-25% reduction), 2 (26%-60% reduction), 1(>60% reduction), or 0 (no reactivity). Any loss of immunoreactivity was proportional to the tissue section age and was least in sections stored in the dark. Immunoreactivity was only completely lost in light-exposed sections and as early as 1 month for CD45. Other markers with complete loss of immunoreactivity were bovine viral diarrhea virus, CD18 (only with fluorescent light), CD31, CD68, canine parvovirus, chromogranins, and thyroid transcription factor-1. Markers with complete loss after light exposure also had reduced immunoreactivity when stored in the dark, as early as day 3. Eight markers (Bartonella spp, CD11d, high molecular weight cytokeratins, feline coronavirus, GATA-4, insulin, p63, progesterone receptor) had minimal decrease in immunoreactivity, regardless of treatment. In conclusion, light-induced antigen decay (tissue section aging) is antigen dependent and could explain unexpectedly weak or negative immunohistochemical reactions in stored paraffin sections.

Histomorphological and immunohistochemical characterization of 172 cutaneous round cell tumours in dogs

This paper describes the use of a panel of antibodies (CD117, CD3, CD79a, CD45, cytokeratin, vimentin and E-cadherin) on formalin-fixed, paraffin-embedded sections of canine cutaneous round cell tumours. Neoplastic tumours were diagnosed by histology and histochemical stains and included 107 mast cell tumours, 31 cutaneous histiocytomas, two localized histiocytic sarcomas, 21 cutaneous lymphomas, three plasma cell tumours, one transmissible venereal tumour and seven unclassified round cell tumours. The histologic diagnosis was modified in 39.5% of the total 172 neoplasms. The staining for CD45 and Ecadherin were variable, and therefore, the final diagnoses of cutaneous histiocytoma and localized histiocytic sarcoma were made based on histology in association with negative results for CD3, CD79a, CD117 and cytokeratin. The cellular origin of unclassified round cell tumours was defined in all cases. Cutaneous B-cell lymphoma and plasma cell tumours were CD79a-positive and could be distinguished from each other by the morphological characteristics. Mast cell tumours and T cell lymphoma were CD117 and CD3 positive, respectively. The positive staining for vimentin and the negative staining for CD3, CD79a, CD117 and cytokeratin favoured the diagnosis of transmissible venereal tumours. Thus, the final diagnosis of cutaneous round cell tumours should be based on the interpretation of immunohistochemical results together with the cellular morphology observed by histology. Therefore, more studies to optimize the specific markers in formalin-fixed, paraffinembedded tissues (especially for histiocytes) are required for definitive diagnosis of round cell tumours in dogs.

Pot-bellied pig neoplasia

The current report summarizes the incidence and variety of neoplasms in pot-bellied pigs as documented by the pathology group at the University of Tennessee, College of Veterinary Medicine (UTCVM) between 2004 and 2011. Sixty-three pot-bellied pig cases (53 necropsies and 10 surgical biopsies) were identified from the UTCVM case database. Of these, 22 cases from 21 patients (34.9%) were given a diagnosis of neoplasia, including 10 females, 3 spayed females, 2 males, and 7 neutered males. The mean age of affected animals was 11.3 years. The incidence of neoplasia among the necropsy cases was 28% (15/53), and in the surgical biopsy material, the incidence was 70% (7/10). Reproductive and gastrointestinal tissues were most commonly affected, and malignancies were frequently identified, with hepatic and intestinal carcinomas predominating. Multiple neoplasms were often identified in patients submitted for necropsy, and in 4 out of 11 of the necropsy cases, at least 1 of the neoplasms was a malignancy. Six necropsy cases revealed metastatic spread.

Hypergammaglobulinemia in an SIV-infected rhesus macaque with a B-cell neoplasm with plasma cell differentiation

An SIV-infected rhesus macaque presented with anemia, hypercalcemia, and hyperglobulinemia. Neoplastic round cells with plasma cell morphology infiltrated multiple organs and stained immunohistochemically positive for CD45, MUM1/IRF4, CD138, VS38C, and Kappa light chain and variably positive for CD20 and CD79a, consistent with a B-cell neoplasm with plasma cell differentiation.

Immunohistochemical Expression of E-cadherin Does Not Distinguish Canine Cutaneous Histiocytoma From Other Canine Round Cell Tumors

Immunohistochemistry for E-cadherin (ECAD) has been used to distinguish canine cutaneous histiocytoma from other leukocytic neoplasms (“round cell tumors”). To determine the specificity of this test, 5 types of canine cutaneous round cell tumors were evaluated for immunohistochemical expression of ECAD. Tumors of all 5 types had variable cytoplasmic, plasma membrane, and/or paranuclear ECAD expression: All 13 cutaneous histiocytomas were ECAD+; all but 1 of 14 mast cell tumors expressed ECAD; 10 of 12 epitheliotropic lymphomas reacted with E-cadherin antibody; of 72 plasmacytomas, 54 were ECAD+; and 5 of 5 histiocytic sarcomas were positive. Conclusions based on these results include the following: First, immunoreactivity for ECAD is not limited to leukocytes of cutaneous histiocytoma; second, antibody to ECAD also labels neoplastic cells in most mast cell tumors, plasmacytomas, cutaneous histiocytic sarcomas, and epitheliotropic lymphomas; third, although most histiocytomas have membranous ECAD expression, the immunoreactivity varies among round cell tumors and is frequently concurrent in different cellular compartments; fourth, the distinctively paranuclear ECAD expression pattern in epitheliotropic lymphomas might distinguish them from other round cell tumors; and, fifth, ECAD should be used with other markers (eg, MUM1 for plasmacytomas, KIT for mast cell tumors, CD3 and CD79a for lymphomas) to distinguish among canine round cell tumors.

Immunohistochemical Identification of Canine Melanocytic Neoplasms With Antibodies to Melanocytic Antigen PNL2 and Tyrosinase

The immunoreactivity of PNL2 and antityrosinase in formalin-fixed, paraffin-embedded canine melanocytic neoplasms ( n = 101) was compared with that of Melan A. Of the 113 samples overall, 106 were positive for PNL2, 101 for Melan A, and 90 for tyrosinase. Six melanomas that were positive for PNL2 were negative for Melan A; 1 melanoma that was negative for PNL2 was positive for Melan A. Eighty tumors were positive for all 3 markers; 111 reacted with at least 1 the 3 antibodies. Decalcification with formic acid for up to 1 week did not affect immunoreactivity of any of the markers; however, decalcification with HCl for 1 day or 1 week notably decreased or completely abrogated immunoreactivity for Melan A and PNL2. There was only minor loss of immunoreactivity for tyrosinase in tissues decalcified with HCl for 1 week. Prolonged fixation (up to 2 months) did not affect PNL2 or tyrosinase immunoreactivity; however, Melan A immunoreactivity was reduced after 1 month of fixation. PNL2 was not expressed in 120 nonmelanocytic tumors (carcinomas, sarcomas, steroid-producing tumors, and leukocytic tumors). In summary, antibody PNL2 is slightly more sensitive than Melan A and more sensitive than tyrosinase in the identification of canine melanocytic neoplasms. Furthermore, PNL2 does not appear to cross-react with nonmelanocytic neoplasms. PNL2 is resistant to prolonged fixation but sensitive to strong decalcification. Results indicate that PNL2 is an excellent marker in the identification of canine melanomas and that the sensitivity is close to 100% when used in conjunction with Melan A and tyrosinase.

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.

Gastric B-Cell Lymphoma with Mott Cell Differentiation in a Dog

A gastric lymphoid tumor with involvement of regional lymph nodes and spleen was diagnosed in an 8-year-old crossbreed male dog with a 6-month history of gastrointestinal disease. Despite surgical excision and palliative therapy (prednisolone and cimetidine), the dog was euthanized due to worsening of clinical signs. At necropsy, multiple white, solid, nodular, infiltrative masses were observed in the stomach, duodenum, spleen, liver, and lungs in association with generalized lymph node enlargement. Cytology, histology, histochemistry, immunohistochemistry, and electron microscopy revealed that the neoplastic cell population was composed of B lymphocytes that contained variable amounts of round periodic acid-Schiff-positive cytoplasmic globules consistent with Russell bodies. The tumor most likely represented a variant of B-cell neoplasia with extensive Mott cell differentiation.

Solitary Intracerebral Plasmacytoma in a Dog: Microscopic, Immunohistochemical, and Molecular Features

A primary intracerebral plasmacytoma was identified in a 7-year-old spayed female Boston Terrier. Grossly, a well-demarcated, 2 cm in diameter, roughly spherical tumor was in the rostral aspect of the left cerebral hemisphere. Histologically, the neoplasm was composed of sheets of round cells with distinct plasmacytoid features and marked anisocytosis and anisokaryosis. Cells were positive for vimentin, CD18, CD79a, and lambda light-chain, and negative for kappa light chain, cytokeratin, lysozyme, glial fibrillary acidic protein, and S100 protein. Clonally rearranged B-cell antigen receptor genes were detected by PARR (polymerase chain reaction for antigen receptor rearrangements), confirming clonal proliferation of B lymphocytes. Although primary solitary intracerebral plasmacytoma is rare in dogs and other species, it should be included in the differential diagnosis for central nervous system round-cell neoplasms. Clonality testing can be utilized to support the histological diagnosis of this neoplasm type.

Suggested Guidelines for Immunohistochemical Techniques in Veterinary Diagnostic Laboratories

This document is the consensus of the American Association of Veterinary Laboratory Diagnosticians (AAVLD) Subcommittee on Standardization of Immunohistochemistry on a set of guidelines for immunohistochemistry (IHC) testing in veterinary laboratories. Immunohistochemistry is a powerful ancillary methodology frequently used in many veterinary laboratories for both diagnostic and research purposes. However, neither standardization nor validation of IHC tests has been completely achieved in veterinary medicine. This document addresses both issues. Topics covered include antibody selection, fixation, antigen retrieval, antibody incubation, antibody dilutions, tissue and reagent controls, buffers, and detection systems. The validation of an IHC test is addressed for both infectious diseases and neoplastic processes. In addition, storage and handling of IHC reagents, interpretation, quality control and assurance, and troubleshooting are also discussed. Proper standardization and validation of IHC will improve the quality of diagnostics in veterinary laboratories.