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Ocular and Periocular Tumors in Cats 2011 WSAVA Jeju Island Korea Richard R Dubielzig

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Page 1: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Ocular and Periocular Tumorsin Cats2011 WSAVA

Jeju Island Korea

Richard R Dubielzig

Page 2: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Anatomic distribution of feline Anatomic distribution of feline primary ocular neoplasia (n = 2599)primary ocular neoplasia (n = 2599)

82%

12.3%

4.4%

1.15%

Page 3: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS
Page 4: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Melanoma: 1510 of 2766 tumors or 55%

– Diffuse Iris Melanoma ... 1340 (263 Early)– “Atypical” ….. 27– Limbal ……… 46– Conjunctival… 27– 70 mostly DIM improperly labeled

Kalishman JV, Chappell R, Flood LA, Dubielzig RR (1998).A matched observational study of survival in cats with enucleation due to diffuse iris melanoma. Vet. Ophthal. 1: 25-29.

Page 5: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Typical Clinical Appearance of Feline Diffuse Iris Melanoma

Asymmetrical Darkening of the IrisThis process can occur rapidly

or it can take years

Page 6: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Typical Histopathologic Appearance of Feline Diffuse Iris Melanoma

Page 7: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Typical Gross Appearance of Feline Diffuse Iris Melanoma

Page 8: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Ages of Cats with Melanosis, Early Melanoma, Melanoma, and Extensive Melanoma

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

Percent of n

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20Age (years)

Progression of Feline DIM

MelanosisEarly DIMDIM (not extensive)Extensive DIM

Melanosis n = 84

Page 9: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Ages of Cats with Melanosis, Early Melanoma, Melanoma, and Extensive Melanoma

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

Percent of n

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20Age (years)

Progression of Feline DIM

MelanosisEarly DIMDIM (not extensive)Extensive DIM

Early Melanoma n = 325

Page 10: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Ages of Cats with Melanosis, Early Melanoma, Melanoma, and Extensive Melanoma

Melanoma (not extensive) n = 1242

Page 11: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Ages of Cats with Melanosis, Early Melanoma, Melanoma, and Extensive Melanoma

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

Percent of n

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20Age (years)

Progression of Feline DIM

MelanosisEarly DIMDIM (not extensive)Extensive DIM

Extensive Melanoma n = 272

Page 12: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Metastatic Potential of Feline Diffuse Iris Melanoma

All of the cases with metastasisin the COPLOW collection wereextensive in the original enucleation

Page 13: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Evisceration Followed by IntrascleralProsthesis is Not Recommended

in Cats with FDIM

Page 14: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Cats with Extensive FDIM atthe Time of Enucleation are MoreLikely to Have a Shortened Life

7 of 9 cats alive at follow-up

6 of 12 cats alive at follow-up

2 of 13 cats alive at follow-up

Page 15: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Early Stages of Feline Diffuse Iris Melanoma:

• Melanosis• Early Melanoma

Page 16: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Melanosis

Proliferating melanocytes are entirely limited to the anterior

surface of the iris

Page 17: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Melanosis

Page 18: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Early FDIMTumor confined to the iris

Page 19: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Early FDIM

Page 20: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Feline Ocular Post-traumatic Sarcoma:234 of 2766 tumors, or ~8%

• Spindle cell variant– 149 cases– Lens epithelial origin

• Round cell variant– 54 cases– Variant of lymphoma

• Osteosarcoma/Chondrosarcoma– 26 OSA cases– 5 Chondrosarcoma cases– Unknown cell of origin

Page 21: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Reasons to believe FOPTS is related to trauma

• Lens capsule rupture• History of trauma or abnormal eye• Time between trauma and tumor

– Between 2 months and 15 years

Page 22: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS
Page 23: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Early Spindle Cell Variant FOPTS

Page 24: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Spindle Cell PTS with

Tumor Distribution in the Spindle Cell Variant

Bone

Page 25: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Feline Ocular Post-traumatic Sarcoma, Spindle Cell Variant

Page 26: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Feline Ocular Post-traumatic Sarcoma,Spindle Cell Variant

Page 27: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Cellular Features of Spindle Cell FOPTS

Collagen 4

Vimentin αA Crystallin

Page 28: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Feline Ocular Post-traumatic Sarcoma,Spindle Cell Variant

Page 29: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Follow-up Spindle Cell Variant

• Cases which have extended beyond the sclera have a bad prognosis– Local recurrence– Extension towards the brain

• Cases removed within the sclera have a good prognosis

• 8% of traumatized globes removed prophylactically have early FOPTS

Page 30: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Round Cell Variant FOPTS

Page 31: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Round Cell PTS

Round Cell Variant FOPTS

Page 32: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Round Cell Variant FOPTS

Page 33: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS
Page 34: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

FOPTS Osteosarcoma

Page 35: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Feline OPTS: Osteosarcoma

Page 36: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Feline Iridociliary Epithelial Tumors

• 102 of 2766 neoplastic cases, ~4%• Tend to be non-pigmented• Solid• Cavitated• About half have metaplastic

bone• Vimentin+, Cytokeratin-

Neglected Feline Iridociliary Adenoma

Page 37: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Feline Iridociliary Epithelial Tumors

Page 38: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Feline Iridociliary Adenoma

Page 39: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Feline Iridociliary Adenoma

Page 40: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Feline Iridociliary AdenomaSpindle Cells

Page 41: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Feline Iridociliary Epithelial TumorsImmunohistochemistry

NSE+ 100%Cytokeratin+ 20%Not related to tumor type

Vimentin+ 34%

Page 42: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS
Page 43: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Feline Conjunctival and Lid Squamous Cell Carcinoma

•Total SCC in the Database: 233•Multifocal (Bowenoid): 15•Orbital: 30•Associated with lymphocytic inflammation: 53•No age or breed associations

Page 44: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Feline Conjunctival and Lid Squamous Cell Carcinoma

Page 45: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Feline Conjunctival and Lid Squamous Cell Carcinoma

Multifocal or Bowenoid

Page 46: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Feline Orbital Squamous Cell CarcinomaDDx Feline Restrictive Orbital Myofibroblastic Sarcoma

Page 47: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Feline Conjunctival and Lid Squamous Cell Carcinoma

Severe Lymphocytic Inflammation

Page 48: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Feline Conjunctival Melanoma•46 cases in the COPLOW database

Page 49: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Feline Conjunctival Surface Adenocarcinoma

•Formerly Mucoepidermoid Carcinoma•18 cases in the COPLOW database•Malignant potential

Page 50: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Feline Conjunctival Surface Adenocarcinoma

Page 51: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Feline Conjunctival Surface AdenocarcinomaMetastatic Potential

L

Page 52: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS
Page 53: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Feline HidrocystomaApocrine gland originSiamese predilection

Page 54: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Feline Eyelid Peripheral Nerve Sheath Tumor

36 cases in the COPLOW Database

S100

Page 55: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Feline Eyelid or ConjuctivalMast Cell Tumors

55 Cases in the COPLOW Database

•All but 3 are cutaneous•Most common at medial canthus

Page 56: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS
Page 57: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Feline Restrictive Orbital MyofibroblasticSarcomaFROMS

(formerly, Feline Orbital Pseudotumor)

Bell CM, Schwarz T, Dubielzig RR. (2011) Diagnostic Features of Feline Restrictive Orbital MyofibroblasticSarcoma. Vet Pathol. 48: 742-750.

Page 58: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

14 cases of FROMS• Breed:

– 9 DSH– 3 DLH– 1 Maine Coon– 1 unknown

• Gender– MN = 5 FS = 9

• Age– Mean = 10.5 years, Median = 10 years– Range = 4 - 16 years

• Unilateral = 13 Bilateral = 1• Oral lesions = 1

Page 59: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Clinical Characteristics• Restricted mobility of globe and eyelids• Thickened and distorted eyelids • Profound corneal disease

Page 60: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

FROMS Clinical Characteristics• Thickening +/- ulceration of lips• Proliferative gingival lesions (neoplastic?)

Page 61: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

•Local extension to adjacent tissues

•Thickening and effacement along fascial planes

Page 62: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

•Severe corneal disease

•Dense, fibrous orbital tissues

•Globe spared

Feline Restrictive Orbital Myofibroblastic Sarcoma

Page 63: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Feline Restrictive Orbital Myofibroblastic Sarcoma

Page 64: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Feline Restrictive Orbital Myofibroblastic Sarcoma

Page 65: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Subepithelial neoplastic cellsare not SMA+, unlike the remainder of the tumor

Smooth Muscle Actin (SMA)

Page 66: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Tooth

Orbit

Orbit from necropsy specimen

Orbit

Tumor in bone

Page 67: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

FROMS Histopathology:

•Spindle cells in irregular short bundles with collagenous matrix

•Bland nuclear profile

•Mitotic activity virtually absent

Trichrome

Page 68: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Total + -Vimentin 8 8 0S-100 8 8 0SMA 8 8 0Melan A 2 0 2

FROMS Immunohistochemistry

Page 69: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Clinical Progression & Survival

• 9 of 10 cases with adequate follow-up had spread to the contralateral eye and/or oral cavity/lips

• All cats (5) that were confirmed deceased were euthanized due to progressive FROMS

• Of 3 cats currently living, 2 have signs of progressive FROMS

Page 70: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Feline Restrictive Orbital Myofibroblastic Sarcoma: Summary

• FROMS behavior is locally invasive and severely restricts the mobility of globe, eyelids and lips

• Morphology suggests an infiltrative myofibroblasticsarcoma, seldom forms a mass lesion, lacks cellular atypia

• Diagnosis requires histopathology plus clinical picture• Distribution and extent in the oral cavity and elsewhere

in the head is not obvious at the first diagnosis but becomes very apparent at necropsy

Page 71: Ocular and Periocular Tumors in Cats€¦ · Typical Clinical Appearance of Feline Diffuse Iris Melanoma Asymmetrical Darkening of the Iris ... Round Cell PTS Round Cell Variant FOPTS

Squamous Cell Carcinomamasquerading as FROMS