Stereotactic radiotherapy for advanced canine anal sac adenocarcinoma: an exploratory study

For dogs with anal sac adenocarcinoma (ASAC), metastasis to intra-abdominal and pelvic lymph nodes occurs early in the disease course. Death is usually related to locoregional progression. Surgical excision is the treatment of choice, but may not be possible in advanced cases. Dogs treated with RT in the gross disease setting showed a 38%-75% overall response rate, but side effects to organs at risk in this area (especially the colon, bladder, and spinal cord) were reported. Stereotactic radiation therapy (SRT) utilizes highly conformal treatment planning with rapid dose fall-off and hypofractionation. SRT may help to reduce the risk of late side effects of radiation while also creating a larger biological effect on ASACs. A primary aim of this prospective, descriptive, exploratory study was to describe the safety and feasibility of an SRT protocol in a small sample of dogs with ASAC, using objective and subjective measures to monitor acute and late side effects. A secondary aim was to describe the anti-tumor response of the SRT protocol using CT at 3- and 6 months posttreatment. Five dogs completed the radiation protocol. Four had follow-up CT characteristics of complete response (1), partial response (2), and stable disease (1). Minimal acute side effects were observed. Despite some large tumor volumes, constraints for OAR were achieved in all but the spinal cord for one patient. Findings indicated that SRT is a safe and feasible treatment for dogs with ACAC. Future studies are warranted to compare patient outcomes for SRT versus other treatments.

Association between total hypercalcaemia and iliosacral lymph node metastasis in dogs diagnosed with anal sac adenocarcinoma using abdominal ultrasonography

BACKGROUND

Anal sac adenocarcinoma (ASACA) in dogs is a malignant perianal tumour that often metastasizes to the iliosacral lymph nodes. Additionally, this tumour can be associated with hypercalcemia of malignancy. To date, no study has looked at the association between increased blood calcium levels and suspected or confirmed lymph node metastasis as a primary objective.

OBJECTIVE

The objective of this study was to determine if increased total serum calcium level is associated with iliosacral lymph node metastasis in dogs diagnosed with ASACA.

METHODS

Medical records of a single referral hospital were searched to identify dogs examined between 2011 and 2021 that had a diagnosis of ASACA via cytology or histopathology. Only dogs that had serum total calcium recorded and abdominal ultrasound were included in the study. All images were reviewed by a board-certified radiologist blinded to any patient identifiers.

RESULTS

Of the 58 dogs, 33% (19/58) had total hypercalcaemia, and of these, 68% had confirmed or suspected iliosacral lymph node metastasis. Total hypercalcaemia was significantly associated with confirmed or suspected iliosacral lymph node metastasis (p < 0.01). However, 46% (11/24) of dogs with confirmed or suspected iliosacral lymph node metastasis were normocalcaemic.

CONCLUSIONS

Based on these results, it is suggested that while the presence of total hypercalcaemia may increase the likelihood of concurrent lymph node metastasis, total hypercalcaemia alone cannot be used as a screening tool for lymph node metastasis. Dogs diagnosed with ASACA should undergo full staging regardless of total serum calcium values.

Long-term outcomes associated with a modified versus traditional closed anal sacculectomy for treatment of canine anal sac neoplasia

OBJECTIVE

To report the short-term and long-term outcomes of dogs that underwent the modified closed and traditional closed anal sacculectomy procedures for the treatment of anal sac neoplasia.

ANIMALS

90 client-owned dogs.

Methods

The medical records of 2 tertiary referral hospitals were reviewed to identify dogs that underwent anal sacculectomy for treatment of anal sac neoplasia between January 2016 and December 2020. Data collected included signalment and preoperative diagnostic findings. The occurrence of intraoperative and postoperative complications, short-term outcomes, and long-term outcomes were also collected. Descriptive statistics were calculated to summarize dog signalment information, and recurrence, metastasis, and survival proportions were compared between techniques using Fisher exact tests.

RESULTS

35 and 55 dogs, respectively, underwent the modified or traditional closed anal sacculectomy procedure. Minor postoperative complications that resolved with minimal intervention occurred in 5 of 35 (14.3%) modified approach dogs and 12 of 55 (21.8%) traditional approach dogs. Tumor recurrence was confirmed in 8 of 35 (22.9%) modified and 8 of 55 (26.4%) traditional approach dogs and was suspected in 3 of 35 (8.6%) and 6 of 55 (13.2%; P = .68), respectively. Confirmed metastatic disease was identified in 8 of 35 (22.9%) and 14 of 53 (26.4%) modified and traditional approach dogs, respectively, and was suspected in 4 of 35 (11.4%) and 7 of 53 (13.2%). Sixty-three (70%) dogs survived to study conclusion.

CLINICAL RELEVANCE

No benefits in complication rate or local recurrence were identified in dogs following the modified approach as opposed to the traditional closed anal sacculectomy technique.

Short- and long-term outcomes associated with anal sacculectomy in dogs with massive apocrine gland anal sac adenocarcinoma

OBJECTIVE

To evaluate short- and long-term outcomes for dogs undergoing anal sacculectomy for massive (> 5 cm) apocrine gland anal sac adenocarcinoma (AGASACA).

ANIMALS

28 client-owned dogs with massive AGASACA.

PROCEDURES

A retrospective multi-institutional study was performed. Pre-, intra-, and post-operative data was collected, and variables were statistically analyzed for associations with progression-free interval (PFI) and overall survival (OS).

RESULTS

At the time of anal sacculectomy, 19 (68%) dogs underwent concurrent iliosacral lymph node extirpation, including 17 of 18 (94%) dogs with suspected nodal metastasis preoperatively. Five (18%) dogs experienced grade 2 intraoperative complications. Ten (36%) dogs experienced postoperative complications, including 1 grade 3 and 1 grade 4 complication. No dogs had permanent fecal incontinence, tenesmus, or anal stenosis. Nineteen dogs received adjuvant chemotherapy, radiation, or both. Local recurrence occurred in 37% of dogs. Dogs with lymph node metastasis at surgery were more likely than dogs without metastasis to develop new/progressive lymph node metastasis (10/17 [59%] vs 0/10 [0%]; P = .003) and distant metastasis (7/17 [41%] vs 0/10 [0%]; P = .026). Median PFI was 204 days (95% CI, 145 to 392). Median OS was 671 days (95% CI, 225 to upper limit not reached). Nodal metastasis at the time of surgery was associated with shorter PFI (P = .017) but not OS (P = .26). Adjuvant therapy was not associated with outcome.

CLINICAL RELEVANCE

Dogs with massive AGASACA experienced prolonged survival following anal sacculectomy despite a high incidence of local recurrence and metastasis. Lymph node metastasis at the time of surgery was a negative prognostic indicator for PFI but not OS.

Complications associated with iliosacral lymphadenectomy in dogs with metastatic apocrine gland anal sac adenocarcinoma

OBJECTIVE

To report intraoperative and immediate postoperative complications associated with removal of metastatic iliosacral lymph nodes in dogs with apocrine gland anal sac adenocarcinoma.

ANIMALS

There were 136 client-owned dogs in the study.

PROCEDURE

Retrospective multi-institutional study. The database of collaborating institutions was searched for dogs with metastatic apocrine gland anal sac adenocarcinoma that underwent lymphadenectomy for removal of one or more iliosacral lymph nodes. Information of signalment, hematological abnormalities, abdominal computed tomography or ultrasound findings, number and size of enlarged lymph nodes, intraoperative and postoperative complications, treatment and outcome were collected.

RESULTS

The overall complication rate associated with metastatic iliosacral lymphadenectomy was 26.1%. The only intraoperative complication recorded was hemorrhage and was reported in 24 (17.6%) surgeries, 11 (45.8%) of which received a blood transfusion. Postoperative complications were reported in 10.4% of surgeries, and included edema formation (n = 4, 2.6%), unilateral or bilateral paraparesis (n = 4, 2.6%), hypotension (n = 3, 2.0%), surgical site infection (n = 2, 1.3%), abdominal incision dehiscence (n = 1, 0.6%), urinary incontinence (n = 1, 0.6%), and death (n = 1, 0.6%). The size of the iliosacral lymph nodes was significantly associated with a greater risk of complications, hemorrhage, and the need of transfusion during lymphadenectomy for metastatic apocrine gland anal sac adenocarcinoma.

CONCLUSION

Complications associated with iliosacral lymphadenectomy for metastatic apocrine gland anal sac adenocarcinoma are relatively common and mostly relate to hemorrhage. These complications are significantly associated with the size of the extirpated metastatic lymph nodes.

CLINICAL RELEVANCE

This retrospective study provides information for the clinician regarding the potential surgical complications for extirpation of metastatic iliosacral lymph nodes. These complications, although not common, can be severe and should be discussed with owners before surgery.

Minimal complications observed with a modified surgical approach for treatment of canine anal sac neoplasia

OBJECTIVE

To describe a modified approach to closed anal sacculectomy and report the short-term outcomes of dogs that underwent the procedure for treatment of neoplasia.

ANIMALS

16 client-owned dogs.

PROCEDURES

Medical records of 1 referral hospital were reviewed to identify dogs that underwent modified closed anal sacculectomy for treatment of anal sac neoplasia between January 2018 and September 2020. Data collected included signalment, examination and diagnostic imaging findings, surgical details, intraoperative and postoperative complications, cytologic and histologic findings, adjuvant treatments, duration of follow-up, and short-term outcome.

RESULTS

15 dogs had apocrine gland anal sac adenocarcinoma, and 1 had a collision tumor. No dogs had intraoperative complications; 1 dog had a minor postoperative complication (paraparesis) that resolved. The median duration of postoperative follow-up was 286 days (range, 67 to 777 days). One dog had confirmed local disease recurrence 290 days after surgery, and 1 had suspected local disease recurrence 203 days after surgery and was euthanized because of systemic disease progression.

CONCLUSIONS AND CLINICAL RELEVANCE

The modified closed anal sacculectomy was well tolerated in this sample of dogs, with minimal short-term complications. This study provided evidence to justify evaluation of the procedure in a larger number of dogs and assessment of the effects of procedural modifications on postoperative complication rates and time to local recurrence.

Pathology of the Emerging Mycobacterium tuberculosis Complex Pathogen, Mycobacterium mungi, in the Banded Mongoose ( Mungos mungo)

Wild banded mongooses ( Mungos mungo) in northeastern Botswana and northwest Zimbabwe are infected with a novel Mycobacterium tuberculosis complex (MTC) pathogen, Mycobacterium mungi. We evaluated gross and histologic lesions in 62 infected mongooses (1999-2017). Many tissues contained multifocal irregular, lymphohistiocytic to granulomatous infiltrates and/or multifocal or coalescing noncaseating to caseating granulomas with variable numbers of intralesional acid-fast bacilli. Over one-third of nasal turbinates examined had submucosal lymphohistiocytic to granulomatous infiltrates, erosion and ulceration of the nasal mucosa, bony remodeling, and nasal distortion. Similar inflammatory cell infiltrates expanded the dermis of the nasal planum with frequent ulceration. However, even in cases with intact epidermis, acid-fast bacilli were present in variable numbers among dermal infiltrates and on the epidermal surface among desquamated cells and debris, most commonly in small crevices or folds. In general, tissue involvement varied among cases but was highest in lymph nodes (50/54, 93%), liver (39/53, 74%), spleen (37/51, 73%), and anal glands/sacs (6/8, 75%). Pulmonary lesions were present in 67% of sampled mongooses (35/52) but only in advanced disseminated disease. The pathological presentation of M. mungi in the banded mongoose is consistent with pathogen shedding occurring through scent-marking behaviors (urine and anal gland secretions) with new infections arising from contact with these contaminated olfactory secretions and percutaneous movement of the pathogen through breaks in the skin, nasal planum, and/or skin of the snout. Given the character and distribution of lesions and the presence of intracellular acid-fast bacilli, we hypothesize that pathogen spread occurs within the body through a hematogenous and/or lymphatic route. Features of prototypical granulomas such as multinucleated giant cells and peripheral fibrosis were rarely present in affected mongooses. Acid-fast bacilli were consistently found intracellularly, even in regions of necrosis. The mongoose genome has a unique deletion (RD1^mon) that includes part of the encoding region for PPE68 (Rv3873), a gene co-operonic with PE35. These proteins can influence the host's cellular immune response to mycobacterial infections, and it remains uncertain how this deletion might contribute to observed patterns of pathology. M. mungi infection in banded mongooses is characterized by both a unique transmission and exposure route, as well as accompanying pathological features, providing an opportunity to increase our understanding of MTC pathogenesis across host-pathogen systems.

Anal Sac Gland Carcinoma in a Cat

A perianal mass in a 15-year-old domestic shorthair cat with a history of a firm, painful swelling in the left ventrolateral perianal region was surgically excised and submitted for light microscopic evaluation. Histologically, this was a poorly demarcated, unencapsulated, multilobulated neoplasm that invaded surrounding perirectal skeletal muscle bundles. Lobules were composed of sheets and acinar arrangements of cuboidal to round neoplastic epithelial cells with scant to moderate eosinophilic to amphophilic cytoplasm and a round or oval nucleus with coarse chromatin. Mitotic figures were 2 per 40 x objective field. Acinar lumina sometimes contained eosinophilic proteinaceous material or cell debris. These microscopic features are consistent with anal sac gland carcinoma. This is the second report of this neoplasm in a cat.

Adjuvant electrochemotherapy for incompletely excised anal sac carcinoma in a dog

Canine anal sac gland carcinoma (ASGC) is a frequently described neoplasm that is highly aggressive and can frequently lead to metastatic spread. In this paper, we describe the successful treatment of an incompletely excised ASGC by using cisplatin selectively driven within the tumor cells by trains of biphasic pulses. The dog received two courses of electrochemotherapy 14 days apart. Neither systemic nor local toxicities were detected during the whole course of therapy. The dog is still in complete remission after 18 months. Electrochemotherapy is a safe and efficacious adjuvant therapy for ASGC and warrants further investigation in order to standardize its protocols.

Clinical stage, therapy, and prognosis in canine anal sac gland carcinoma

BACKGROUND

Reports of canine anal sac gland carcinoma (ASGC) describe varied clinical presentations and management and differing responses to therapy. A unifying approach to clinical stage determination and management of this disease has yet to be presented.

HYPOTHESIS

An ordinal clinical staging scheme for canine ASGC can be devised on the basis of responses to therapy for a retrospective cohort of affected dogs.

ANIMALS

130 dogs with naturally occurring ASGC.

METHODS

A simplified clinical stage system and a management algorithm for canine ASGC were derived from retrospective evaluation of a cohort of 80 dogs; applicability of both was then prospectively evaluated in a cohort of 50 dogs.

RESULTS

Retrospective evaluation revealed 4 statistically significant negative prognostic indicators for survival: lack of therapy, presence of distant metastases, presence of lymph node metastases, and primary tumor size. Lymph node extirpation was a statistically significant positive prognostic indicator by bivariate analysis. In both retrospective and prospective analyses, the modified clinical stage scheme revealed a significant association with survival time.

CONCLUSIONS AND CLINICAL IMPORTANCE

The clinical staging scheme permits differentiation between groups in terms of prognosis and, therefore, decisions on therapy. This will facilitate application of appropriate therapy and enhanced communication and collaboration in further investigations of ASGC.

Metastatic anal sac adenocarcinoma in a dog presenting for acute paralysis

A 4-year old, female spayed terrier was referred for hind end paresis that rapidly progressed to paralysis. Spinal radiographs revealed vertebral collapse and bony lysis. Myelography confirmed spinal cord compression and surgical exploration found an extradural soft tissue mass. Metastatic anal sac adenocarcinoma was diagnosed at postmortem examination.

Electrolyte Disturbances and Cardiac Arrhythmias in a Dog Following Pamidronate, Calcitonin, and Furosemide Administration for Hypercalcemia of Malignancy

A 13-year-old dog was diagnosed with hypercalcemia of malignancy associated with adenocarcinoma of the anal sacs. Hypercalcemia was treated with intravenous (IV) 0.9% sodium chloride (NaCl), furosemide, calcitonin, and pamidronate. Hypomagnesemia was documented by 72 hours following a single, IV dose of pamidronate. The dog subsequently underwent surgery to remove the primary tumors, and multiple cardiac arrhythmias occurred during anesthesia. This case documents electrolyte abnormalities in a dog following treatment with pamidronate in conjunction with other therapies used to manage hypercalcemia. The authors postulate that hypomagnesemia may have contributed to the arrhythmias that occurred during anesthesia. Electrolyte abnormalities should be anticipated and corrected following pamidronate therapy in canine patients.

Carcinoma of the apocrine glands of the anal sac in dogs: 113 cases (1985–1995)

OBJECTIVE

To characterize the signalment, clinical signs, biological behavior, and response to treatment of carcinoma of the apocrine glands of the anal sac in dogs.

DESIGN

Retrospective study.

ANIMALS

113 dogs with histologically confirmed carcinoma of the apocrine glands of the anal sac.

PROCEDURE

Data on signalment, clinical signs, and staging were reviewed and analyzed along with treatment modality for potential association with survival time.

RESULTS

Sex distribution was approximately equal (54% female, 46% male). One hundred four dogs underwent treatment consisting of surgery, radiation therapy, chemotherapy, or multimodal treatment. Median survival for treated dogs was 544 days (range, 0 to 1,873 days). Dogs treated with chemotherapy alone had significantly shorter survival (median, 212 days) than those receiving other treatments (median, 584 days). Dogs not treated with surgery had significantly shorter survival (median, 402 days) than those that underwent surgery as part of their treatment (median, 548 days). Dogs with tumors > or = 10 cm2 had significantly shorter survival (median, 292 days) than dogs with tumors < 10 cm2 (median, 584 days). Hypercalcemia was identified in 27% (n = 29) of dogs, and those dogs had significantly shorter survival (median, 256 days), compared with those that were normocalcemic (median, 584 days). Dogs with pulmonary metastasis had significantly shorter survival (median, 219 days) than dogs without evidence of pulmonary metastasis (median, 548 days).

CONCLUSIONS AND CLINICAL RELEVANCE

Unlike most previous reports, this study revealed an approximately equal sex distribution, and results suggest a more favorable prognosis.

Squamous cell carcinoma of the anal sac in five dogs

Tumors of the perianal area of dogs are common and include multiple tumor types. Whereas perianal adenomas occur often, adenocarcinomas of the apocrine glands of the anal sac occur less frequently. A review of the literature revealed no reports of squamous cell carcinomas arising from the epithelial lining of the anal sac. Squamous cell carcinomas originating from the lining of the anal sac were diagnosed in five dogs. Microscopically, the tumors consisted of variably sized invasive nests and cords of epithelial cells displaying squamous differentiation. Four of the five dogs were euthanatized because of problems associated with local infiltration by the tumors. In the fifth dog, there was no evidence of tumor 7 months after surgical removal, but further follow up was not available.

Antibiotic-responsive generalized nonlesional pruritus in a dog

A 15-year-old dog was evaluated for a nonresponsive generalized pruritic condition of 5 months duration. Routine diagnostic testing, including intradermal testing with 63 inhaled allergens and the feeding of a home-cooked hypoallergenic diet, failed to define the cause of the pruritus. An intradermal skin test with a staphylococcal cell wall/toxoid mixture and a skin biopsy of the skin test site suggested that the dog had a bacterial hypersensitivity. Antibiotic therapy eliminated the pruritus and the dog's pruritus was successfully managed for 3 years with the combined use of subtherapeutic dosages of antibiotics and a commercial staphylococcal vaccine.

[Epithelium and anal glands in rectal pouches and fistula. Histologic studies of swine with congenital anal atresia]

The epithelial coating of the rectal pouch and fistula was studied morphologically in 33 newborn piglets with high and low forms of anal atresia and was found to be similar to the epithelial coating of the anal canal in normal piglets: the typical epithelium of the rectum changed its character into transitional epithelium at the region of the internal sphincter which surrounded the fistulae in all animals. In the caudal part of the fistula the transitional epithelium was followed by squamous epithelium. Only in male piglets with deformities and recto-urethral fistulae no squamous epithelium was found. In these cases transitional epithelium covered all parts of the fistula and the region of the internal sphincter. Anal glands were found in all animals, with or without anorectal malformations. They always invaded the internal sphincter. According to our morphological studies the fistula in anorectal malformations represents an ectopic anal canal.

Adenylate cyclase-stimulating, bone-resorbing and B TGF-like activities in canine apocrine cell adenocarcinoma of the anal sac

Canine apocrine cell adenocarcinoma of the anal sac (APO-AS) is a spontaneously occurring tumor that causes humorally mediated hypercalcemia in 90% of cases. To further define the nature of the responsible mediator in APO-AS, we examined tumor extracts from five APO-AS and four control tumors for adenylate cyclase-stimulating activity (ACSA). All extracts from APO-AS contained potent ACSA, whereas the four control tumors did not. The ACSA extracted from one tumor demonstrated a dose response curve parallel to that of synthetic bovinePTH-(1-34) and was 80% inhibited by Nle8,18,Tyr34 bPTH-(3-34)amide at a concentration of 10(-5) M. Extracts from three APO-AS and three control tumors were also examined for in vitro bone-resorbing activity (BRA). All APO-AS contained significant BRA, stimulating resorption 1.47 to 2.13-fold over basal, whereas none of the control tumors stimulated resorption. Purification of one extract using C18 reverse-phase high pressure liquid chromatography (RP-HPLC) resulted in a single sharp peak of ACSA which was 400-fold purified compared with the initial extract. This pool also contained significant bone-resorbing activity, whereas none of the adjacent pools did. Purification of a second extract using sequential CN and C18 RP-HPLC followed by size exclusion HPLC resulted in material that was at least 10,000-fold purified, and showed co-purification of ACSA and B TGF-like activity.

Hypercalcemia of malignancy: Hypercalcemia associated with an adenocarcinoma of the apocrine glands of the anal sac

Images

Hypercalcemia associated with an adenocarcinoma derived from the apocrine glands of the anal sac

Clinical, gross, and light microscopic findings are described for 36 dogs, 33 females and three males, with adenocarcinomas arising from the apocrine glands of the anal sac. All tumors had light microscopic features of malignancy and 22 of 23 metastasized to iliac and lumbar lymph nodes. Nine dogs had disseminated metastases, but bone metastases were found in only one dog. Differentiated neoplasms formed secretory acini and tubules lined by tall columnar or cuboidal epithelium. Most neoplasms were histologically bimorphic, with glandular areas and solid nests. Parathyroid glands were atrophic. Hypercalcemia (mean = 16.1 mg/dl) was present in 20 of 22 dogs (90%) and hypophosphatemia (mean = 3.2 mg/dl) in 12 of 17 (71%). Remission of hypercalcemia by tumor ablation and recurrence of hypercalcemia with tumor regrowth suggested that the tumor produced a substance that caused hypercalcemia. This unique clinicopathologic syndrome is characterized by hypercalcemia in old, predominantly female, dogs with an adenocarcinoma arising from the apocrine glands of the anal sac.