SOFT TISSUE TUMORS OF FELINE SKIN AND SUBCUTIS
Following on from the general useage of the term 'Soft Tissue Sarcoma' and soft tissue sarcoma grading of the mid 1980s in dogs, many people use the term 'soft tissue sarcoma' in cats. I personally dont like this, because soft tissue sarcoma is a group diagnosis, and many people, clinicians included, use it as a specific diagnosis. Combining fibrous tumors, lipocytic tumors, vascular wall tumors, feline injection site sarcoma (in all its various forms) is done because, appart from FISS, there are unsufficient cases with followup to provide an accurate prognosis. Even in FISS, the grading scheme is of little usage.
Dobromylskyj et al (2021) published a series of tumors of soft tissues in 47 cats that had followup. These were graded using the system that combined mitotic count, percentage necrosis, and degree of 'inflammation'. 16 cases were Grade 1 and 3 died of tumor related disease. 2 of these 3 had no treatment and 1 had reoccurrance. The MST was 900 days. 15 were grade 2, 8 died of tumor related disease, mostly reoccurrence. Of the 16 with Grade III tumors, 11 died of tumor related disease. Reoccurrance, lack of treatment and suspected metastasis was the cause of tumor related disease. 22 of the 47 died of tumor related disease. These had a median mitotic count of 21. 21 did not die of tumor related disease but the median survival was only 205 days. Those that were alive at the end of the study had a MST of 854 days. The median mitotic count was 9. Overall the number developing metastasis was very low (while not confirmed, 4 of the 47 likely developed metastatic disease). Reoccurrence or a decision not to treat was the major reasons for tumor related disease.
Dobromylskyj MJ, Richards V, Smith KC. Prognostic factors and proposed grading system for cutaneous and subcutaneous soft tissue sarcomas in cats, based on a retrospective study. J Feline Med Surg. 2021; 23: 168-174.
Conventional Fibroma and Fibrosarcoma
Feline Injection Site Sarcoma (FISS)
FISS is a neoplasm that arises at sites of injection in the cat. It most commonly occurs at sites of vaccination.
Margins:
There are many studies of surgical margins and recurrence. The current recommendation is 5cm and 2 fascial planes deep (for interscapular tumors) and a body wall resection in those of the lateral thorax or flank.
Reexcisions had the highest liklihood of recurrence.
Müller N, Kessler M. Curative-intent radical en bloc resection using a minimum of a 3 cm margin in feline injection-site sarcomas: a retrospective analysis of 131 cases. J Feline Med Surg. 2018; 20: 509-519.
Myofibroblastic Fibroma and Fibrosarcoma
Feline restrictive orbital myofibroblastic sarcoma
Immunohistochemistry: neoplastic cells stain with vimentin, SMA and S100
Schöniger S, Tivers MS, Baines SJ, Summers BA Arteriovenous haemangioma in two dogs and a cat. J Comp Pathol 2008; 139: 130-136
Miller et al (1992) reported on 15 cats with vascular tumors; 7 were hemangiomas and 9 were hemangiosarcoma. No hemangioma reoccurred after excision.
Miller MA, Ramos JA, Kreeger JM. Cutaneous vascular neoplasia in 15 cats: clinical, morphologic, and immunohistochemical studies. Vet Pathol. 1992; 29: 329-336.
Miller et al (1992) reported on 15 cats with vascular tumors; 7 were hemangiomas and 9 were hemangiosarcoma. 6 of 9 cases were euthanased from 2 to 17 months after diagnsosis. Reoccurrences were common. Metastasis was not determined - no postmortem examinations. Those on the head and ears were considered solar induced.
McAbee et al (2005) reported on 18 cases. 2 were dermal and 16 were subcutaneous. 1 had complete excision and no reccurrence. 1 did not have surgery and increased in size until the end of the study.
Johannes et al (2007) reported on 53 cats with hemangiosarcoma. 7 were in the dermis and 1 died of disease and 6 individuals were censored.
McGrath et al (2022) reported on 5 cats with hemangiosarcoma of the nasal planum. They were treated with surgery and 4 were given radiation therapy. Survival was in excess of 331 days.
Miller MA, Ramos JA, Kreeger JM. Cutaneous vascular neoplasia in 15 cats: clinical, morphologic, and immunohistochemical studies. Vet Pathol. 1992; 29: 329-336.
Johannes CM, Henry CJ, Turnquist SE, Hamilton TA, Smith AN, Chun R, Tyler JW. Hemangiosarcoma in cats: 53 cases (1992-2002). J Am Vet Med Assoc. 2007; 231: 1851-1856.
McAbee KP, Ludwig LL, Bergman PJ, Newman SJ. Feline cutaneous hemangiosarcoma: a retrospective study of 18 cases (1998-2003). J Am Anim Hosp Assoc. 2005; 41: 110-116.
McGrath AM, Cook MR, Culp WT, Oblak ML, Oramas A, Bertran J, Tremolada G, Lapsley J, Selmic LE. Hemangiosarcoma of the nasal planum in cats: five cases (2010-2021). J Feline Med Surg. 2022; 24: e661-e666.
Johannes et al (2007) reported on 53 cats with hemangiosarcoma. 6 were subcutaneous. 4 died and 2 were censored.
McAbee et al (2005) reported on 18 cases of which. 2 were dermal and 16 were subcutaneous. 4 had complete excision and no recurrence. 1 had incomplete excision and recurred. The rest died of other disease - if surgery was done, the interval to death was longer than 360 days. If surgery was not done, the interval was short and for many 60 days.
Johannes CM, Henry CJ, Turnquist SE, Hamilton TA, Smith AN, Chun R, Tyler JW. Hemangiosarcoma in cats: 53 cases (1992-2002). J Am Vet Med Assoc. 2007; 231: 1851-1856.
Baron CP, Puntel FC, Fukushima FB, da Cunha O. Progressive cutaneous angiomatosis in the metatarsal region of a cat. J Am Vet Med Assoc. 2020;256: 226-229
This entity is often misdiagnosed as angiosarcoma.
papilla have endothelial lining but the cells dont stain for endothelial cells - they stain SMA+ or are reactive fibroblastic.
Godizzi F, Caniatti M, Treggiari E, Romanelli G, Bonfanti U, Ghisleni G, Roccabianca P. Extravascular papillary endothelial hyperplasia mimicking soft tissue sarcoma in 2 cats: a potential diagnostic pitfall. J Vet Diagn Invest. 2022; 34: 552-557
Lymphangioma
Lyumphangiosarcoma
Lymphangiomatosis
Congential Lymphatic malformation
While this is not a neoplasm, it can appear to be neoplastic or at least is a differential diagnosis for neoplasia.
This entity must be present at birth or soon after. It is the result of dilated vascular spaces that are lymphatic vessels. These do not form a mass (and are not lymphangiomas) but rather form vascular structures separated from each other or they are serpigenous.
Legnani S, Abramo F, Zanna G, Graziano L, Cornegliani L, Roccabianca P. Acral congenital superficial dermal lymphatic malformations in two unrelated cats: clinicopathological, dermoscopic and ultrastructural findings. Vet Dermatol. 2020; 31: 309-e77.
Schulman et al (2009) reported on 53 cats with 59 tumors. There was variation in the pattern of the cells. All had fine wavy delicate cobweb like cytoplasmic processes. Many had the apperarance of nerve rootless. 9 had verocay bodies. Some had Antoni B acellular matrix surrounded by a cellular region (Antoni A). Hyaline change of blood vessels may be present. Some had cells with nuclei with ancient change - karyomagalic cells with hyperchromatic nuclei. They were spindle cell tumors that were all positive with vimentin and S100, and 44 were positive for GFAP. 9 recurred and none were metastatic.
Schulman FY, Johnson TO, Facemire PR, Fanburg-Smith JC. Feline peripheral nerve sheath tumors: histologic, immunohistochemical, and clinicopathologic correlation (59 tumors in 53 cats). Vet Pathol. 2009; 46: 1166-1180.
Benign nerve sheath tumor
Neurolemmoma
Neurofibroma
Perineurinoma
Malignant nerve sheath tumor
Granular cell tumor
Patnaik (1993) reported on the presence of a granular cell tumor in the digit of a cat. It was presumably in the skin. It reoccurred after surgery.
Patnaik AK. Histologic and immunohistochemical studies of granular cell tumors in seven dogs, three cats, one horse, and one bird. Vet Pathol. 1993 Mar;30(2):176-85.
Guisado and Castro (2022) reported on 9 affected cats. Six of 9 were cured by excision, 2 recurred and 1 was metastatic to the local lymph node. Clinical outcome was influenced by mitotic count (above 10) and degree of infiltration. The cells aretypical of smooth muscle tumor, but 7 of the 9 had giant cells and bizzare nucle, atypical mitoses and 6 had necrosis. Cells were calponin, desmin and smooth muscle actin positive.
Guisado FR, Castro PL. Piloleiomyosarcoma in cats: Histological and immunohistochemical features. Vet Pathol. 2022 Jan;59(1):57-62. doi: 10.1177/03009858211042582. Epub 2021 Sep 16. PMID: 34525874.
Embryonal
Rhabdomyoblastic
round cells and strap cells
Myotubular
Chang et al (2006) reported a rhabdosarcoma at a vaccine site. It was metastatic to lungs. It appeared to be an embryonal, myotubular type.
Miller et al. 2009 reported on a case in a a 14 month old cat. It had metastases at 21 months of age.
Miller AD, Steffey M, Alcaraz A, Cooper B. Embryonal rhabdomyosarcoma in a young Maine coon cat. J Am Anim Hosp Assoc. 2009; 45: 43-47.
Chang HW, Ho SY, Lo HF, Tu YC, Jeng CR, Liu CH, Wang FI, Pang VF. Vaccine-associated rhabdomyosarcoma with spinal epidural invasion and pulmonary metastasis in a cat. Vet Pathol. 2006 Jan;43(1):55-8. doi: 10.1354/vp.43-1-55. PMID: 16407487.
Botryoid
Pleomorphic
Alveolar
Craig et al (2020) reported on 16 cats. Synovial cysts were present in 14 cases. 2 cases had myxomas only, 3 had synovial cysts only and 11 had both. There was transition between myxomatous change and myxoma. The medial surface of the elbow is the most common region affected.
Craig LE, Krimer PM, O'Toole AD. Synovial Cysts and Myxomas in 16 Cats. Vet Pathol. 2020; 57: 554-558.
Soft tissue chondrosarcoma is exceptionally rare.
There is a case report of an extraskeletal chondrosarcoma of the subcutis in a 4 year old cat - it was on the dorsal lumbosacral region. No vaccination, trauma or other causative agent was identified. It was a mesenchymal chondrosarcoma. There were no metastases or reoccurrence after 6 months..
Romanucci M, Bongiovanni L, Petrizzi L, della Salda L. Cutaneous extraskeletal mesenchymal chondrosarcoma in a cat. Vet Dermatol. 2005 Apr;16(2):121-4. doi: 10.1111/j.1365-3164.2005.00429.x. PMID: 15842543.