Melanocytoma-acanthoma in a Dog

Background: Melanocytic neoplasms are skin tumors that often occur in dogs.  However, melanocytoma-acanthoma, also called melanoacanthoma, is a benign melanocytic neoplasm rarely reported in this species, which has been described only three times in the veterinary literature. Briefly, this tumor is characterized by a single, painless, darkly pigmented and firm cutaneous papule or nodule. Histologically, it is composed of mixed populations of well-differentiated melanocytes and keratinocytes, unlike traditional melanocytic tumors (melanoma and melanocytoma). These cells are arranged in lobules surrounded by collagenous stroma. Melanocytes are large epithelioid cells containing varying amounts of melanin. Keratinocytes form anastomosing trabeculae with peripheral palisading, and small cysts containing amorphous or laminated keratin. The definitive diagnosis of melanocytoma-acanthoma is based on histopathological findings. This report describes a case of melanocytoma-acanthoma in a dog in Brazil.Case: A 9-year-old female miniature Schnauzer dog was examined at the Veterinary Hospital of the Federal University of Santa Maria, where a single, firm, pigmented papule was found in the auricle. The lesion had started 15 days earlier. Hematological tests and serum biochemistry profile were normal. An excisional biopsy of the papule was surgically removed and subjected to histopathological examination. The tissue was fixed in 10% neutral buffered formalin, processed routinely and embedded in paraffin wax. Sections were stained with hematoxylin and eosin (HE). A histopathological examination revealed a nonencapsulated, well-defined, extensive, densely cellular proliferation located in dermis. This proliferation was composed of lobules and nests of well-differentiated stratified squamous epithelium closely associated with neoplastic melanocytes, surrounded by thin bundles of fibrous stroma. A diagnosis of melanocytoma-acanthoma was established based on these histological features.Discussion: The first description of melanocytoma-acanthoma in humans was as melano-epithelioma, classified into subtypes I and II. Both subtypes are benign neoplasms composed of well-differentiated melanocytes and keratinocytes, which are distinguished from one another based on the amount and distribution of melanocytes. Type I melano-epithelioma is characterized by proliferative lobules of melanocytes and keratinocytes, including melanocytes scattered diffusely among keratinocytes. Type II melano-epithelioma involves only the proliferation of keratinocytes, while melanocytes are limited to the basal layer of keratinocyte lobules. To clarify this condition, some authors use the term “melanoacanthoma” to indicate the above-described type I melano-epithelioma, and seborrheic keratosis to indicate type II melano-epithelioma. However, other authors use the term melanoacanthoma to denote the two conditions (types I and II melano-epithelioma). On the other hand, veterinary medicine does not recognize subtypes, instead using the term melanocytoma-acanthoma, and more recently, melanoacanthoma, to denote this cutaneous neoplasm. Melanocytoma-acanthoma in dogs was first reported in Spain, and involved a 2-year-old German shepherd dog. Later, two other cases were described in adult mixed-breed dogs, one in South Korea and the other in Libya. This is the first report of melanocytoma-acanthoma in a dog in Brazil. The gross and histopathological appearance of this case matches that described in the previous cases (a single, well-defined, pigmented cutaneous papule or nodule). Histologically, the differential diagnosis for melanocytoma-acanthoma includes melanoma, melanocytoma, trichoepithelioma, and sebaceous epithelioma.

Melanocytoma-acanthoma in a Dog

Background: Melanocytic neoplasms are skin tumors that often occur in dogs.  However, melanocytoma-acanthoma, also called melanoacanthoma, is a benign melanocytic neoplasm rarely reported in this species, which has been described only three times in the veterinary literature. Briefly, this tumor is characterized by a single, painless, darkly pigmented and firm cutaneous papule or nodule. Histologically, it is composed of mixed populations of well-differentiated melanocytes and keratinocytes, unlike traditional melanocytic tumors (melanoma and melanocytoma). These cells are arranged in lobules surrounded by collagenous stroma. Melanocytes are large epithelioid cells containing varying amounts of melanin. Keratinocytes form anastomosing trabeculae with peripheral palisading, and small cysts containing amorphous or laminated keratin. The definitive diagnosis of melanocytoma-acanthoma is based on histopathological findings. This report describes a case of melanocytoma-acanthoma in a dog in Brazil.Case: A 9-year-old female miniature Schnauzer dog was examined at the Veterinary Hospital of the Federal University of Santa Maria, where a single, firm, pigmented papule was found in the auricle. The lesion had started 15 days earlier. Hematological tests and serum biochemistry profile were normal. An excisional biopsy of the papule was surgically removed and subjected to histopathological examination. The tissue was fixed in 10% neutral buffered formalin, processed routinely and embedded in paraffin wax. Sections were stained with hematoxylin and eosin (HE). A histopathological examination revealed a nonencapsulated, well-defined, extensive, densely cellular proliferation located in dermis. This proliferation was composed of lobules and nests of well-differentiated stratified squamous epithelium closely associated with neoplastic melanocytes, surrounded by thin bundles of fibrous stroma. A diagnosis of melanocytoma-acanthoma was established based on these histological features.Discussion: The first description of melanocytoma-acanthoma in humans was as melano-epithelioma, classified into subtypes I and II. Both subtypes are benign neoplasms composed of well-differentiated melanocytes and keratinocytes, which are distinguished from one another based on the amount and distribution of melanocytes. Type I melano-epithelioma is characterized by proliferative lobules of melanocytes and keratinocytes, including melanocytes scattered diffusely among keratinocytes. Type II melano-epithelioma involves only the proliferation of keratinocytes, while melanocytes are limited to the basal layer of keratinocyte lobules. To clarify this condition, some authors use the term “melanoacanthoma” to indicate the above-described type I melano-epithelioma, and seborrheic keratosis to indicate type II melano-epithelioma. However, other authors use the term melanoacanthoma to denote the two conditions (types I and II melano-epithelioma). On the other hand, veterinary medicine does not recognize subtypes, instead using the term melanocytoma-acanthoma, and more recently, melanoacanthoma, to denote this cutaneous neoplasm. Melanocytoma-acanthoma in dogs was first reported in Spain, and involved a 2-year-old German shepherd dog. Later, two other cases were described in adult mixed-breed dogs, one in South Korea and the other in Libya. This is the first report of melanocytoma-acanthoma in a dog in Brazil. The gross and histopathological appearance of this case matches that described in the previous cases (a single, well-defined, pigmented cutaneous papule or nodule). Histologically, the differential diagnosis for melanocytoma-acanthoma includes melanoma, melanocytoma, trichoepithelioma, and sebaceous epithelioma.

Hemolytic Crisis in a Dog with Copper-Associated Chronic Hepatitis

Background: Copper is an essential micronutrient for the body to function properly. However, although it is a vital element, an excess of copper in the body is extremely toxic. Copper toxicity has been reported mainly in sheep. In dogs, clinicopathological signs of toxicity are characterized by chronic liver failure. This means that the hemolytic crisis so common in sheep is a condition rarely associated with toxicity in dogs, so there are very few descriptions of this condition in the veterinary literature. The purpose of this report is to describe a case of hemolytic crisis in a dog with copper-associated chronic hepatitis.Case: A medium-sized 6-year-old bitch was brought to the Veterinary Hospital of the Federal University of Santa Maria, with clinical presentation of apathy, anorexia and red urine. A physical examination revealed mildly jaundiced mucosa and dark brown urine. A urinalysis indicated the presence of protein, bilirubin and occult blood. The blood count revealed hypochromic macrocytic anemia, leukocytosis due to left shift neutrophilia and thrombocytopenia. Serum biochemistry showed elevated levels of alanine aminotransferase and alkaline phosphatase. The animal was given a blood transfusion due to the severity of her anemia, but her clinical condition worsened and she died, whereupon her body was sent for necropsy. This necropsy revealed conspicuous signs of jaundice, splenomegaly and altered liver and kidney color. The liver was brownish, with its natural surface firm and slightly irregular. The kidneys were diffusely blackened. The urine was dark brown. Fragments of different organs were collected, fixed in 10% buffered formalin solution, routinely processed for histopathology and stained with hematoxylin and eosin. A histological dissection of the liver showed the hepatic lobes dissected by fibrosis, forming islands of hepatocytes and numerous lymphocytes and plasmocytes. Brown granular pigment was observed in periportal hepatocytes. Perls Prussian blue and rubeanic acid staining techniques were performed to characterize this pigment. Most of the pigment reacted strongly to rubeanic acid and but not to Perls’ Prussian blue, thus characterizing it as copper. Random hepatic necrosis was visible. The kidneys contained hemoglobin and necrotic epithelial cells obstructing the renal tubules. Based on the clinical and anatomopathological aspects, a diagnosis of hemolytic crisis due to copper-associated chronic hepatitis was established.Discussion: The most accepted mechanism to explain the occurrence of hemolysis is that copper long stored in hepatocytes is massively released into the bloodstream due to some stressful condition. When too much copper circulates in the bloodstream it inhibits enzymes that act on the energy metabolism of red blood cells, thereby lowering the synthesis of energy and nucleotides needed for glutathione activity, and causing hemoglobin to transform into methemoglobin. In the case reported here, copper toxicosis presumably originated from the animal’s diet since, according to the literature, the periportal distribution of copper revealed during histology suggests that the event resulted from excessive copper intake or was secondary to previous cholestatic liver injury. This paper describes a case of hemolytic crisis in a dog with copper-associated chronic hepatitis and, emphasizes the importance of including copper toxicity as a differential diagnosis for dogs presenting hemolytic crisis, in order to assist veterinarians in managing their patients.

Ancillary techniques on the evaluation of canine cutaneous mast cell tumors from Brazil

ABSTRACT: The use of histologic classification by a 2-tier grading system only, immunohistochemistry (IHC) for KIT and Ki-67 and polymerase chain reaction (PCR) for internal tandem duplications (ITD) on exon 11 has improved the prognostication of canine cutaneous mast cell tumors (CCMTs) particularly in the United States. However, these techniques are not commonly used in most Brazilian laboratories. Likewise, no studies, to date, have investigated the occurrence of ITD in CCMTs from the country. Thus, this study tested the 2-tier grading system, the immunohistochemistry for KIT and Ki-67 and the PCR for exon 11 in a group of Brazilian CCMTs with the goal of investigating the applicability of these tests in a Brazilian laboratory. Of the 39 CCMTs, 69.2% (27/39) were identified as low-grade and 30.8% (12/39) as high-grade by a 2-tier grading system. All tumors had a KIT expression pattern II, and 30.6% (11/36) had a high growth fraction (Ki-67). PCR amplification was successful in four of the 11 tumors examined. Two of these (50%) were positive for ITD. This study highlights the importance of using auxiliary techniques in the CCMT evaluation, identifies limitations and confirms the applicability of these methods on a routine diagnostic basis in Brazil. Our results will help to improve the prognostication of CCMTs in Brazilian diagnostic laboratories, encouraging the use of supplementary methods