Squamous cell carcinoma of the anal sacs in three dogs

Comparison of computed tomography findings between perianal tumors originating from the anal sacs and perianal glands in dogs

Tumors originating from the anal sacs and perianal glands are common tumors of the perianal region. However, differentiation of perianal tumors based on CT findings remains challenging because perianal tumors can show overlapping CT characteristics. Therefore, this retrospective, multi-institutional study aimed to identify the CT findings that can differentiate between tumors originating from the anal sacs and perianal glands in canines. Twenty dogs were included, with nine apocrine gland anal sac adenocarcinomas (AGASACAs), six perianal gland adenomas, three perianal gland carcinomas, and two perianal gland epitheliomas. The tumor CT features included the tumor growth pattern, tumor shape, cystic changes within the tumor, contrast enhancement pattern, displacement of the anus, and identification of the anal sacs. The prevalences of suspected metastatic lymphadenopathy of the iliosacral lymph centers and lung metastases were evaluated. The tumor volumes and values normalized to body weight were also assessed. The tumor growth patterns differed significantly between AGASACAs and perianal gland tumors. AGASACAs mostly showed unilateral growth, whereas perianal gland tumors mostly exhibited bilateral growth. CT features, except for the tumor growth pattern, failed to show significant differences between tumors arising from the anal sacs and those arising from the perianal glands. Although histopathological diagnosis remains the gold standard, this study's findings suggest that CT analysis of tumor growth patterns may help differentiate AGASACAs from perianal gland tumors.

Quantification of Canine Apocrine Gland Anal Sac Adenocarcinoma (AGASACA) Tumor Specimen Shrinkage after Formalin Fixation

Simple Summary

As the evidence in apocrine gland anal sac adenocarcinoma tumors grows, it is becoming more evident that stage-specific treatment strategies will become the mainstay. Thus, having confidence in the measurements of primary tumors is paramount. We aimed to quantify the degree of tumor tissue shrinkage after 24 and 48 h of formalin fixation to guide clinicians in their use of post-fixation measurements. We prospectively enrolled 23 client-owned dogs with naturally occurring apocrine gland anal sac adenocarcinoma that underwent surgical resection of at least the primary tumor. Measurements were recorded immediately before being placed in 10% buffered formalin and then again after 24 and 48 h of fixation, respectively. Overall, we found that tumors shrank by a mean of 4.8% and 7.2% after 24 and 48 h, respectively. This in real terms was a median of 1 mm. Other factors associated with the tumor, like the predominant microscopic pattern, the amount of necrosis, or the amount of fibrovascular stroma, did not have an impact on the degree of shrinkage. This study shows that the degree of shrinkage following formalin fixation should not impact the use of post-fixation measurements and can be used in clinical staging schema.

Abstract

The aim was to prospectively measure the shrinkage of primary apocrine gland anal sac adenocarcinoma (AGASACA) tumors after 24 and 48 h of formalin fixation. Dogs that were diagnosed with AGASACA pre-operatively by aspiration cytology were prospectively enrolled in the study. Tumor extirpation was performed in a closed technique. The tumor and associated tissues were examined on the back table away from the patient and the widest dimension of the tumor was measured using a sterile ruler (Medline^®; Northfield, IL, USA). This measurement was recorded in mm (t₀). The tissue was placed in 10% buffered formalin and stored at room temperature. Two further measurements were taken after 24 (t₂₄) and 48 (t₄₈) hours of formalin fixation. Once the 48 h measurement was taken, the tissue was submitted for histopathology. The percentage of shrinkage between time points was calculated by using the following equation: (1 − [time b/time a]) × 100. Overall, 23 dogs with 23 tumors were enrolled. The mean percentage of shrinkage after 24 and 48 h of formalin fixation was 4.8% and 7.2%, respectively. The median diameter of the tumors reduced by 1 mm over 48 h and was not significantly different at any time point. These data will aid clinicians in interpreting measurements of AGASACA tumors following formalin fixation and shows that minimal change in tumor size is expected following 48 h.

Canine Apocrine Gland Anal Sac Adenocarcinoma: A Review

Apocrine gland anal sac adenocarcinoma (AGASAC) is a relatively uncommon tumor in the dog and comprises approximately 17% of perianal malignancies; however, it is one of the most common causes of paraneoplastic hypercalcemia. Clinical signs in affected dogs most commonly are associated with mechanical obstruction caused by the primary tumor or enlarged regional metastatic lymph nodes and the effects of paraneoplastic hypercalcemia when present. Surgical excision of the primary tumor and metastasectomy of affected locoregional lymph nodes is the preferred initial treatment option for most dogs, although radiation therapy and adjuvant chemotherapy are commonly incorporated into multi-modality treatment plans. A significant role for the use of adjuvant chemotherapy has not been clearly demonstrated. Prolonged survival times are possible, especially for dogs with smaller primary tumors and for dogs that undergo further treatments for recurrent disease. In this article, we review the clinical signs, diagnosis, staging, treatment, and prognosis of AGASAC in the dog.

Anal sacculiths may be an incidental finding in dogs

Mineral-attenuating material is occasionally seen in the anal sacs of dogs during abdominal CT studies. This retrospective, descriptive study was performed to estimate the prevalence and CT appearance of this mineral-attenuating material. A total of 357 abdominal CTs were reviewed retrospectively. The mineral-attenuating material was most easily identifiable using the brain window setting (window width: 120 HU; window level: 40 HU). In the current study, the prevalence of mineral-attenuating material in the anal sacs was 7.6% (95% confidence interval, 5.0-10.8%) with 48.1% bilateral involvement and equal distribution in the right and left in dogs with unilateral involvement. Successful collection and material analysis were performed in three dogs. The material was determined to be 100% dried blood, 100% waxy matter, and a "small amount of fat enmeshed in unidentified noncrystallined material." Given the CT appearance and the Hounsfield unit of these mineral-attenuating material within the anal sacs, the term "anal sacculiths" is proposed. All dogs with anal sacculiths within this study population did not have any reported disease of the anal sacs.

Squamous cell carcinoma of the anal sac in two cats

This report describes two cases of feline anal sac squamous cell carcinoma. Cat 1 was managed with a multimodal approach combining surgical resection, radiation therapy and systemic therapy (toceranib phosphate; Palladia™) until local recurrence was identified at 236 days postsurgery. At that time, the cat received carboplatin. With the tumour being progressive, the cat was euthanased 552 days post initial surgery. Cat 2 was managed palliatively with a non-steroidal anti-inflammatory (meloxicam) and supportive medications. Unfortunately, with further decline in quality of life following initial diagnosis, the cat was euthanased 28 days later. Squamous cell carcinoma should be considered as a possible differential diagnosis when a cat is presented for investigation of an anal sac mass.

Complete Resolution of a Recurrent Canine Anal Sac Squamous Cell Carcinoma with Palliative Radiotherapy and Carboplatin Chemotherapy

Anal sac squamous cell carcinoma (SCC) is a rare tumor in dogs. Only eight cases have been described in the literature, and previous reports of treatment only describe surgery or palliative treatment with non-steroidal anti-inflammatory drugs. We report a case of a 12-year-old female neutered Labrador with locally advanced anal sac SCC. The dog was treated with four cycles of carboplatin 300 mg/m² and four weekly fractions of 8.5 Gy radiation. The dog achieved a complete response, and one year later the dog is still alive and well with no evidence of tumor recurrence. Radiotherapy in combination with carboplatin chemotherapy was effective in the long-term control of this rare disease.

p16 Immunostaining of Canine Squamous Cell Carcinomas Is Not Associated with Papillomaviral DNA

While papillomavirus (PVs) are an established cause of human cancer, few reports have supported a relationship between PV and canine squamous cell carcinomas (SCCs). Human oncogenic PVs lead to an increased expression of the p16 tumor suppressor protein, and the latter can be demonstrated immunohistochemically to support a likely causal relationship between tumor and PV infection. In the present study, archive samples of canine SCC from different anatomical locations were tested by polymerase chain reaction for the presence of PV DNA and by p16 immunohistochemistry. The aims were to investigate the relationship between p16 expression and presence of PV DNA, in order to assess the utility of p16 overexpression as a biomarker of PV infection in canine SCC. A total of 52 SCCs were included. Nine cases (17.3%) showed moderate p16 immunoreactivity, with no association with tumor degree of differentiation, histotype or mitotic activity. The canPVf/FAP64 primers amplified Canis familiaris PV-1 DNA from 3 out of 52 tumors (5.8%), one cutaneous, one oral and one tonsillar SCC. There was no association between PV presence and p16 immunostaining. These results do not support a significant role of PVs in the development of canine SCCs. Additionally, PV infection was apparently not the cause of the p16 immunostaining observed in a subset of canine SCCs. A better awareness of p16 level of expression and cellular function in canine cancer may help to define its diagnostic and prognostic role.