JPC SYSTEMIC PATHOLOGY
Signalment (V04-14822): Tissue from a cat
HISTOPATHOLOGIC DESCRIPTION: Haired skin and bone, digit: Expanding the dermis, elevating the overlying multifocally hyperplastic epidermis and infiltrating the bone is an unencapsulated, poorly demarcated moderately cellular neoplasm composed of respiratory epithelial cells arranged in islands and acini on a dense desmoplastic stroma. Neoplastic cells are columnar to cuboidal with cilia lining their apical surface, they have distinct cell borders, a moderate amount of eosinophilic granular cytoplasm, a round to oval nucleus that is located on the basilar surface with finely stippled chromatin and one distinct nucleolus. There is moderate anisocytosis and anisokaryosis. The mitotic count is 2 per 10 HPF. Multifocally within the neoplasm there is single cells necrosis. There is a focally extensive area in the superficial dermis composed of increased numbers of small caliber blood vessels that are oriented perpendicular to the epidermis admixed with occasional neutrophils and separated by clear space (edema) (granulation tissue). The overlying epidermis is moderately hyperplastic with acanthosis, spongiosis and rete ridge formation.
MORPHOLOGIC DIAGNOSIS: Haired skin and bone: Metastatic pulmonary carcinoma, feline.
DISEASE: Lung-digit syndrome
- Pulmonary carcinoma is the most common cause of tumor metastasis to the skin in cats
- They have a high propensity to metastasize to the digit due to the high digital blood flow and weight-bearing function of the digit; however they can metastasize to other sites in the skin
- Metastasis usually occurs prior to the onset of clinical signs from the primary neoplasm
- Common in older cats but there is no breed or sex predilection
TYPICAL CLINICAL FINDINGS:
- Lameness with minimal to absent pulmonary signs
- Radiographic evidence of the digit reveals bony lysis of the phalanx
- Thoracic radiographs classically reveal a single, large, circumscribed mass in the caudal left lung field
TYPICAL GROSS FINDINGS:
- Lesions are suggestive of paronychia
- May have lesions on multiple digits or on the nail bed, dewclaw is excluded
- Swelling, skin ulceration, purulent discharge may be present
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- Nests, solid sheets and glandular structures formed by malignant epithelial cells in the dermis and subcutis
- Neoplastic cells have abundant eosinophilic cytoplasm, basally oriented nuclei, and frequent apical cilia
- Lumens may contain necrotic cellular debris
- Squamous differentiation is common
- Desmoplasia is usually present
- Mitotic activity is variable
- Bony lysis of the third phalanx
- May involve multiple digits
ADDITIONAL DIAGNOSTIC TESTS:
- Special stains:
- Neoplastic cells within metastatic lesions often contain and secrete mucin which would stain PAS (+) whereas primary adenocarcinomas of the digit would be PAS (-)
- 2 (CK7/8) and CK13 useful for glandular neoplasms
- Squamous cell carcinoma is most common digit tumor followed by fibrosarcoma
- Bacterial and fungal paronychia
- Immune mediated disease
- Primary cutaneous apocrine or eccrine carcinoma should be considered if ciliated epithelium is not present
- Eccrine carcinomas are rare
- Bony invasion by an apocrine adenocarcinoma is unlikely
- Cutaneous metastasis of transitional cell carcinoma has been reported after abdominal surgery; most cases cutaneous lesions are close to the vulva or prepuce, possible that urine may seed the neoplastic cells to scalded skin
- Visceral hemangiosarcomas may metastasize to the subcutis
- Mammary gland carcinomas may metastasize to the dermis of the inner thigh
- Llama report of cutaneous metastasis of mammary adenocarcinoma
- Gross TL, Ihrke PJ, Walder EJ, Affolter VK. Skin diseases of the dog and cat. 2nd ed., Oxford, UK: Blackwell Science; 2005: 706.
- Mauldin EA, Peters-Kennedy J. Integumentary system. In: Maxie MG, ed. Jubb, Kennedy and Palmer’s Pathology of Domestic Animals. Vol 1. 6th ed. Philadelphia, PA: Elsevier Ltd; 2016:736.
- Petterino C, Guazzi P, Ferro S, Castagnaro. Bronchogenic adenocarcinoma in a cat: An unusual case of metastasis to the skin. Vet Clin Pathol. 2005;34:401-404.
- Schaffer PA, Barnes S. Pathology in practice. 2016;249(2):157-160.
- Vobornik S, Johnson M, Diesel A, Simpler R. What is your diagnosis? Aspirate from a digit in a cat. Vet Clin Pathol. 2014;43(2):291-292.
- Wobeser BK, Kidney BA, Powers BE, Winthro SJ, Mayer MN, Spinato MT, Allen AL. Diagnoses and clinical outcomes associated with surgically amputated feline digits submitted to multiple diagnostic laboratories. Vet Pathol. 2007;44:362-365.