The Dog with Nodules
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Updated:
JUN 13, 2006
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Key Questions
> How old was this patient when clinical signs were first recognized?
> How long has the disease been present and how did it progress?
> Are there any other animals in the household?
> Does anybody in the household have skin disease?
> Was the disease treated before? If so, which drugs were used and how successful was treatment?
Differential Diagnoses
The differential diagnoses are predicted primarily based on two separate features: (1) Is there only one lesion (which increases the likelihood of neoplasia or a kerion) or are there multiple lesions (which may be due to sterile inflammatory diseases, more aggressive neoplastic disease or severe infection); and (2) Are draining tracts absent or present (increasing the likelihood of foreign bodies, severe bacterial or fungal infection, or sterile inflammatory disease)?
The approach to the dog with nodules is straightforward. History and clinical examination are followed by microscopic evaluation of impression smears (if draining tracts are present) and aspirates in any dog with nodules. In some patients, cytology will reveal an infectious organism or classic neoplastic cells and thus a diagnosis. In most patients, cytological examination will further narrow the list of differential diagnoses, but a biopsy will be necessary to reach a diagnosis. With nodular lesions, complete excision of one or more nodules should be performed. If draining tracts are present and/or cytology indicates possible infection, a culture may be useful as well. Deep tissue should be submitted rather than a culture swab.
Table 2-6. Differential Diagnoses, Commonly Affected Sites, Recommended Diagnostic Tests, Treatment Options, and Prognosis in a Dog with Nodules | ||||
Disease | Commonly Affected Sites | Diagnostic Tests | Treatment | Prognosis |
Abscesses (caused by bite wounds or foreign bodies) | Fluctuating nodules most commonly around neck, shoulders and tail base | Cytology | Surgical drainage, antibacterial treatment | Good. |
Neoplasia* | Varies with individual neoplastic diseases (Fig 2-36 and Fig. 2-37) | Cytology,biopsy | Surgical excision and/or tumor specific therapy | Poor to excellent depending on the individual tumor. |
Sterile granulomatous and pyogranulomatous disease* (unknown pathogenesis) | Firm, painless, nonpruritic dermal papules, plaques and nodules typically of head, pinnae and distal limbs (Fig. 2-38) | Cytology, biopsy , culture, | Doxycycline/niacinamide, immunosuppressive therapy | Fair with appropriate management. |
Sterile panniculitis* (mostly unknown pathogenesis, occasionally due to lupus erythematosus) | Solitary lesion over chest, neck or abdomen, multiple trunkal lesions with concurrent anorexia, lethargy, pyrexia (Fig. 2-39) | Biopsy | Surgical excision for solitary lesions; vitamin E or systemic glucocorticoids for systemic disease | Fair with appropriate management. |
Opportunistic mycobacterial infection* (ubiquitous, facultative pathogenic organisms, e.g., Mycobacteria fortuitum, M. chelonei, M. smegmatis cause lesions after traumatic implantation into subcutaneous tissue) | Non-healing ulcerated nodules with draining tracts. | Biopsy, culture | Wide surgical excision followed by combination antimicrobial therapy. | Fair to guarded. |
Dermatophyte kerion (caused by dermatophytes and secondary bacterial infection) | Nodular furunculosis with draining tracts (Fig. 2-40) | Cytology, biopsy, fungal culture. | Antimycotic and concurrent antibacterial therapy | Good. |
Cryptococcosis* (Rare infection in often immunocompromized host with ubiquitous, saprophytic, yeast-like fungus Cryptococcus neoformans) | Upper respiratory, cutaneous, central nervous and ocular signs. Papules, nodules, ulcers and draining tracts. Nose, lips, and claw beds may be affected. | Cytology, biopsy , fungal culture , serologic testing | Antimycotic therapy with amphotericin B possibly in combination with ketoconazole or itraconazole | Fair. |
Bacterial pseudomycetoma (non-branching bacteria, such as coagulase-positive Staphylococciimplanted during trauma, form grains of compact colonies surrounded by pyogranulomatous inflammation) | Firm nodules with draining fistulae | Cytology, biopsy, bacterial culture | Complete surgical excision, post-surgical antibacterial treatment | Fair with complete excision, guarded, if this is not possible. |
Sporotrichosis* (caused by ubiquitous dimorphic fungal saprophyte Sporothrix schenkiithat infects wounds). Zoonosis, although zoonotic potential of canine sporotrichosis is much lower than that of feline sporotrichosis | Multiple nodules or ulcerated plaques on the head, pinnae, and trunk. | Biopsy, fungal culture | Antimycotic therapy with iodides or azoles | Fair. |
Eumycotic mycetoma (ubiquitous soil saprophytes cause disease through wound contamination) | Nodules with draining tracts and scar tissue. Grains vary in size, shape, and color. | Cytology, biopsy , culture | Wide surgical excision followed by antimycotic therapy based on in vitrosusceptibility testing. | Fair to guarded depending on surgical excision. |
Phaeohyphomycosis* (wound contamination by ubiquitous saprophytic fungi with pigmented hyphae) | Often solitary subcutaneous nodules on extremities. | Cytology, biopsy, culture | Wide surgical excision followed by antimycotic therapy based on in vitrosusceptibility testing | Guarded. |
Actinomycosis* (traumatic implantation of or wound contamination with filamentous, anaerobic Actinomyces spp., commensals of the oral cavity and bowel) | Subcutaneous swellings, possibly with draining tracts and yellow sulfur granules | Cytology, biopsy , culture | Surgical excision followed by long term antibacterial therapy | Guarded. |
Actinobacillosis* (oral commensal aerobic Actinobacillus ligneriesiiis traumatically implanted, often through bite wounds) | Thick-walled abscesses of the head, mouth, and limbs that discharge thick pus with soft, yellow granules. | Cytology, biopsy , culture | Surgical excision or drainage and long-term antibacterial therapy | Guarded. |
Blastomycosis* (rare infection by the dimorphic saprophytic fungus Blastomyces dermatitides). Possible zoonosis (through wound contamination) | Papules, nodules, subcutaneous abscesses with draining tracts on face and feet. Concurrent anorexia, weight loss, coughing, dyspnea, ocular disease | Cytology, biopsy, fungal culture | Guarded to poor, if central nervous system (CNS) involved and poor for vision, if uveitis is present. | |
Coccidioidomycosis* (rare infection with dimorphic, saprophytic fungus Coccidioides immitis) | Papules, nodules, abscesses, and draining tracts over infected bones. Concurrent anorexia, weight loss, coughing, dyspnea, ocular disease, CNS signs possible | Biopsy, fungal culture | Guarded (reported overall recovery rate 60%) to poor (with bone involvement). | |
Histoplasmosis* (uncommon infection with dimorphic, saprophytic soil fungus Histoplasma capsulatum) | Papules, nodules, ulcers, and draining tracts. Concurrent anorexia, weight loss and fever, coughing, dyspnea, gastrointestinal and ocular disease | Cytology, biopsy , fungal culture | Fair to good for dogs with pulmonary disease, guarded to grave for disseminated disease. | |
Nocardiosis* (Nocardia spp. are soil saprophytes and cause respiratory, cutaneous, or disseminated infections) | Ulcerated nodules and abscesses, often with draining tracts, on the limbs and feet | Cytology, biopsy , culture | Surgical drainage and antibacterial therapybased on in vitrosusceptibility testing | Guarded. |
Pythiosis* (infection with aquatic fungi by exposure of damaged skin to infected stagnant water) | Ulcerated nodules of the face and legs develop into boggy masses with ulceration and draining tracts | Biopsy, culture | Wide surgical excision | Guarded to poor. |
Tuberculosis* (rare infection in small animals caused by Mycobacterium tuberculosis, bovis and rarely avium, predominantly respiratory and digestive lesions) | Ulcers, plaques, and nodules on head, neck, and limbs that discharge yellow-green pus with unpleasant smell | Radiographs, biopsy, culture | Combination antimicrobial therapy, frequent euthanasia due to public health concerns | Poor. |
Figure 2-36. Histiocytoma in a 2-year-old castrated Jack Russell mixed breed.
Figure 2-37. Sebaceous cysts in a castrated Boxer (Courtesy of Dr. Sonya Bettenay).
Figure 2-38. Nodules and ulcers in a 2-year-old spayed Maltese with sterile granulomatous disease.
Figure 2-39. Sterile panniculitis with ulcers and nodules in a 9-year-old castrated English Springer Spaniel.
Figure 2-40. Dermatophyte kerion (Courtesy of Dr. Sonya Bettenay).
Figure 2-41. The Dog with Nodules
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How to reference this publication (Harvard system)?
(2006) “The Dog with Nodules”, Dermatology for the Small Animal Practitioner. Available at: https://www.ivis.org/library/dermatology-for-small-animal-practitioner/dog-nodules (Accessed: 06 October 2024).
Affiliation of the authors at the time of publication
Department of Clinical Sciences, Coll. of Veterinary Medicine & Biomedical Sciences, Colorado State University, Fort Collins, CO, USA.
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ISBN-10
1893441091
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