Immunohistochemical and Histochemical Stains for Differentiating Canine Cutaneous Round Cell Tumors

Abstract

Abstract. Immunohistochemical and histochemical stains are useful adjunct techniques in the diagnosis of canine cutaneous round cell tumors, which can appear histologically similar. We applied a panel of monoclonal antibodies (recognizing tryptase, chymase, serotonin for mast cells; CD1a, CD18, MHC class II for histiocytes; CD3 for T lymphocytes; CD79a for B lymphocytes and plasma cells) and one histochemical stain (naphthol AS-D chloroacetate for chymase activity) to formalin-fixed, paraffin-embedded sections of canine cutaneous mast cell tumors, histiocytomas, lymphosarcomas, plasmacytomas, and unidentified round cell tumors. Of 21 tumors with a histologic diagnosis of mast cell tumor, 7/7 (100%) grade I, 6/7 (85.7%) grade II, and 3/7 (42.9%) grade III tumors were diagnosed as mast cell tumors based on positive staining for tryptase antigen and chymase activity. Mast cells were positive for both tryptase antigen and chymase activity, indicating equal efficacy of tryptase immunohistochemistry and chymase histochemistry. Chymase was detected immunohistochemically in both tumor and nontumor cells, while serotonin was not detected in most mast cell tumors, and thus, neither was useful in the diagnosis of mast cell tumors. Immunohistochemistry to detect CD18 and MHC class II was equally effective in staining histiocytomas, although lymphosarcoma must be ruled out through the use of CD3 and CD79a immunohistochemistry. Immunohistochemistry using three different monoclonal antibodies to human CD1a showed no cross-reactivity in canine histiocytomas and was not useful. A final diagnosis was obtained for 4/5 (80%) of the unidentified tumors, indicating the usefulness of multiple stains in poorly differentiated round cell tumors.

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

“…Cutaneous round cell tumours may have a similar morphological appearance, and a diagnosis based only on routine histopathology is often challenging (Fernandez et al 2005). Among these neoplasms are mast cell tumours (MCT) with intermediate differentiation, or grade II, mast cell tumours poorly differentiated, or grade III, cutaneous T-cell lymphoma (CTL), cutaneous B-cell lymphoma (CBL), plasma cell tumours (PCT), cutaneous histiocytomas (HCT) and transmissible venereal tumours (TVT) (Goldschimidt & Hendrick 2002).…”

“…Among these neoplasms are mast cell tumours (MCT) with intermediate differentiation, or grade II, mast cell tumours poorly differentiated, or grade III, cutaneous T-cell lymphoma (CTL), cutaneous B-cell lymphoma (CBL), plasma cell tumours (PCT), cutaneous histiocytomas (HCT) and transmissible venereal tumours (TVT) (Goldschimidt & Hendrick 2002). Accurate diagnosis is essential to determine a prognosis and treatment (Fernandez et al 2005). Immunohistochemistry (IHC) has been proven to be one of the most important ancillary techniques in the characterization of neoplastic diseases in veterinary medicine, as oncologists demand more speciϐic diagnoses (Ramos-Vara et al 2008).…”

Canine oral cavity T-cell lymphoma – histopathological and immunohistochemical study

“…Due to an unusual location, oral lymphomas in dogs must be differentiated from other round-cell tumours of the oral cavity. The antibody panel designed primarily for the differentiation of canine cutaneous round-cell tumours includes major histocompatibility complex class II (MHCII) and CD18, which are markers of histiocytic cells; tryptase, which is specific for mast cells; and the lymphocytic markers CD3 and CD79a (1). The same panel can also be used for the differentiation of the main types of oral cavity round-cell tumours.…”

Cytomorphometry of canine cutaneous histiocytoma

“…Additional stains, including toluidine blue and immunohistochemistry (MHCII,CD18,CD3,CD79a) are most useful for the differentiation of canine cutaneous round cell tumors (Fernandez et al 2005). Nuclear morphometry has been shown to be an effective auxiliary tool for differential diagnosis of histiocytoma, mastocytoma and transmissible venereal tumor in dogs (De Andrade Waldemarin et al 2004).…”