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The Cat with Nodules
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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 other clinical signs such as sneezing, coughing, or diarrhea?
> Was the disease treated before? If so, which drugs were used and how successful was treatment?
Differential Diagnoses
The differential diagnoses depend primarily on two features: the number of lesions and whether draining tracts are present or not. Is there only one lesion? This increases the likelihood of neoplasia or a kerion. Or are there multiple lesions? These may be due to sterile inflammatory diseases, more aggressive neoplastic disease, or severe infection. The presence of draining tracts increases the likelihood of foreign bodies, severe bacterial or fungal infection, or sterile inflammatory disease.
In a cat with nodules, history taking and clinical examination are followed by microscopic evaluation of impression smears (if draining tracts are present) and aspirates (in any cat with nodules). In some patients, cytology will reveal an infectious organism or classic neoplastic cells and thus a diagnosis. In most patients, cytology will aid in further limiting the list of differential diagnoses, but a biopsy will be necessary to reach a diagnosis. With nodular lesions, a complete excision of one or more nodules should be performed. If draining tracts are present and/or cytology indicates possible infection, a tissue culture may be useful as well.
Table 2-11. Differential Diagnoses, Commonly Affected Sites, and Recommended Diagnostic Tests in a Cat with Nodules | |||
Disease | Commonly Affected Sites | Treatment | Prognosis |
Neoplasia* | Varies with individual neoplastic diseases | Surgical excision and/or tumor specific therapy | Poor to excellent depending on the individual tumor. |
Abscesses (caused by bite wounds or foreign bodies) | Fluctuating nodules most commonly around neck, shoulders, and tail base | Surgical drainage, antibacterial treatment | Good |
Opportunistic mycobacterial infection* (ubiquitous, facultatively pathogenic organisms such as Mycobacteria fortuitum, M. chelonei, M. smegmatis, cause lesions after traumatic implantation into subcutaneous tissue) | Nonhealing ulcerated nodules with draining tracts predominantly in the abdominal or inguinal area (Fig. 2-58and Fig.2-59). | Wide surgical excision followed by combination antimicrobial therapy | Fair with appropriate surgical approach |
Cryptococcosis* (uncommon infection of sometimes immunocompromised host with ubiquitous, saprophytic, yeast-like fungus Cryptococcus neoformans) | Upper respiratory, cutaneous, central nervous system, and ocular signs. Firm swelling over the bridge of the nose (Fig. 2-60), papules, nodules, ulcers and draining tracts. Nose, lips, and claw beds may be affected. | Antimycotic therapy with azoles and/or amphotericin B | Fair |
Bacterial pseudomycetoma (nonbranching bacteria such as coagulase-positive Staphylococciimplanted by trauma form grains of compact colonies surrounded by pyogranulomatous inflammation; rare disease) | Firm nodules with draining fistulae (Fig. 2-61) | Complete surgical excision, postsurgical antibacterial treatment | Fair with complete excision; guarded, if this is not possible. |
Eumycotic mycetoma (ubiquitous soil saprophytes cause disease through wound contamination; rare disease) | Nodules with draining tracts and scar tissue. Grains vary in size, shape, and color. | Wide surgical excision followed by antimycotic therapy based on in vitro susceptibility testing. | Fair to guarded depending on surgical excision. |
Feline Leprosy* (presumably transmission of an incompletely characterized mycobacterium that is difficult to culture through bite wounds from rats; rare disease in veterinary dermatology) | Single or multiple, nonpainful and nonpruritic nodules on head and limbs; sometimes ulcers and fistulae are present (Fig. 2-62a and Fig. 2-62b) | Surgical excision, combination antibiotic therapy | Fair |
Actinobacillosis* (Oral commensal aerobic Actinobacillus ligneriesii is traumatically implanted, often through bite wounds; rare disease in veterinary dermatology) | Thick-walled abscesses of the head, mouth, and limbs discharging thick pus with soft yellow granules. | Surgical excision or drainage and long-term antibacterial therapy with streptomycin, chloramphenicol, sodium iodide or tetracyclines | Guarded |
Histoplasmosis (uncommon infection with dimorphic, saprophytic soil fungus Histoplasma capsulatum; very rare disease in veterinary dermatology) | Papules, nodules, ulcers, and draining tracts with concurrent anorexia, weight loss, and fever; dyspnea and ocular disease | Antimycotic therapy with azoles, possibly in combination with amphotericin B | Guarded to grave |
Nocardiosis* (Nocardia spp. are soil saprophytes that cause respiratory, cutaneous, or disseminated infections; very rare disease in veterinary dermatology) | Ulcerated nodules and abscesses, often with draining tracts, on the limbs and ventral abdomen | Surgical drainage, antibacterial therapy based on in vitrosusceptibility testing. | Guarded |
Phaeohyphomycosis* (wound contamination by ubiquitous saprophytic fungi with pigmented hyphae; very rare disease in veterinary dermatology | Often solitary subcutaneous nodules on nose, trunk, or extremities | Wide surgical excision followed by antimycotic therapy based on in vitro susceptibility testing. | Guarded |
Plague (infection with Yersinia pestisby inhalation of organism or through wound contamination or flea bites; very rare disease in veterinary dermatology) Zoonosis: Spread through transmission of infected fleas, presentation of infected killed rodents, or direct infection! | High fever, depression, anorexia, and abscesses typically on the face or limbs in the bubonic form. Septicemic and pneumonic forms also exist. | Flea control, draining of abscesses, antibacterial therapy with tetracycline, streptomycin, or chloramphenicol | Fair, if recognized and treated promptly. |
Sporotrichosis* (caused by ubiquitous dimorphic fungal saprophyte Sporothrix schenkii that infects wounds; uncommon disease in veterinary dermatology) Zoonosis: Transmission to humans through contact with an ulcerated wound easily possible! | Multiple nodules or ulcerated plaques on the head, distal limbs, tailbase (Fig. 2-63). Anorexia, lethargy, fever, and depression possible concurrently | Antimycotic therapy with iodides or azoles | Fair |
Sterile granulomatous and pyogranulomatous disease (unknown pathogenesis) | Firm, painless, nonpruritic dermal papules, plaques, and nodules typically on head and pinnae | Doxycycline / Niacinamide, immunosuppressive therapy, may resolve spontaneously | Fair |
Sterile panniculitis (unknown pathogenesis) | Solitary nodules on ventral rump | Surgical excision | Good |
Tuberculosis* (very rare in small animal dermatology; predominantly respiratory and digestive lesions) | Insidious ulcers, plaques, and nodules on head, neck, and limbs discharging yellow-green pus with unpleasant odor | Combination antimicrobial therapy, frequent euthanasia (public health concerns) | Poor |
Figure 2-58. A 5-year-old castrated domestic shorthair (DSH) with nodules and draining tracts resulting from atypical mycobacteria (Courtesy of Dr. Sonya Bettenay).
Figure 2-59. Draining tracts due to atypical mycobacteria in a 3-year-old castrated DSH.
Figure 2-60. Nasal swelling caused by cryptococcosis in a 6-year- old female domestic long-hair cat. (Courtesy of Dr. Thierry Olivry).
Figure 2-61. Pseudomycetoma in a Persian cat (Courtesy of Dr. Peter Ihrke).
Figure 2-62a. Feline leprosy in a DSH (Courtesy of Dr. Peter Ihrke).
Figure 2-62b. Close up of feline leprosy in a DSH (Courtesy of Dr. Peter Ihrke).
Figure 2-63. Nasal ulceration in a 2-year-old castrated DSH with sporotrichosis.
Figure 2-64. The cat with nodules.
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Department of Clinical Sciences Coll. of Veterinary Medicine & Biomedical Sciences, Colorado State University, Fort Collins, CO, USA.
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