JPC SYSTEMIC PATHOLOGY

INTEGUMENTARY SYSTEM

September 2016

I-N01

 

SLIDE A
Signalment (JPC #2794788):  German shepherd dog

HISTORY:  This mass is from the neck.

HISTOPATHOLOGIC DESCRIPTION:  Haired skin:  Focally expanding the dermis is a 6 x 8 mm, well circumscribed cystic neoplasm composed of basaloid polygonal cells arranged in islands, cords, and trabeculae that form a complex cyst wall, exhibit gradual keratinization, and line a large keratin filled cyst that is contiguous with the epidermis forming a large central pore.  Multifocally, thin anastomosing cords of neoplastic cells project radially from the basal epithelium and are supported by a moderate fibrovascular and myxomatous stroma.  Neoplastic cells are polygonal, have generally distinct cell borders, moderate amounts of eosinophilic cytoplasm, round to oval nuclei, finely stippled chromatin, and one usually distinct nucleolus.  The mitotic rate averages one per ten HPFs.  Multifocally cords form variably sized cysts lined by gradually keratinizing epithelium and are filled with lamellated keratin (horn cysts). Within the adjacent dermis there are low numbers of lymphocytes and plasma cells.

MORPHOLOGIC DIAGNOSIS:  Haired skin:  Infundibular keratinizing acanthoma, German shepherd dog, canine.

CONDITION:  Infundibular keratinizing acanthoma

SYNONYMS:  Intracutaneous cornifying epithelioma, keratoacanthoma

SLIDE B
Signalment (JPC #2657259):  Adult mixed breed dog

HISTORY:  Dermal mass

HISTOPATHOLOGIC DESCRIPTION:  Haired skin:  Expanding the subcutis and elevating the dermis and epidermis is a 10 x 20 mm, unencapsulated, well-circumscribed, multiloculated neoplasm composed of islands, nests, and broad cords of basaloid polygonal cells supported by a moderate fibrovascular stroma.  Neoplastic cells undergo incomplete trichogenesis.  Islands and nests of neoplastic cells form large keratin filled cysts and exhibit both gradual keratinization, characterized by a normal transition from basal cells to squamous cells, and abrupt keratinization, which is characterized by direct transition of basal to keratinized squamous cells, which lack keratohyalin granules and have faded nuclei (ghost cells).  Neoplastic cells have indistinct cell borders, small amounts of eosinophilic cytoplasm, round to oval nuclei, coarsely stippled chromatin, and indistinct nucleoli.  Mitoses average 1 to 2 per HPF. Cysts contain variable amounts of myxomatous and homogenous eosinophilic material (keratin). The dermis is diffusely edematous characterized by increased clear space between collagen bundles and multifocal ectatic lymphatics. There are few mast cells and plasma cells infiltrating the dermis.

MORPHOLOGIC DIAGNOSIS:  Haired skin:  Trichoepithelioma, breed not specified, canine.

SLIDE C
Signalment (JPC #1620817):  1-year-old dog

HISTORY:  Cystic mass removed from the head.

HISTOPATHOLOGIC DESCRIPTION:  Haired skin:  Expanding the dermis and subcutis and extending to the margins of the submitted tissue is an unencapsulated, moderately well-circumscribed neoplasm composed of islands of polygonal cells supported by a loosely arranged fibrovascular stroma.  Neoplastic cells undergo incomplete recapitulation of the outer root sheath of the hair bulb.  Neoplastic cells palisade along a prominent eosinophilic basal lamina zone, have indistinct cell borders, abundant pale eosinophilic often vacuolated cytoplasm, irregularly round to oval vesiculate nuclei, and contain one often distinct nucleolus.  Mitotic figures average one per HPF.  Multifocally centrally located cells have deeper eosinophilic, fibrillar cytoplasm.  Multifocally cells contain brown granular material (melanin).

MORPHOLOGIC DIAGNOSIS:  Haired skin:  Tricholemmoma, inferior (bulb) type, breed not specified, canine.

SLIDE D
Signalment (21474-40):  Dog

HISTORY:  Dermal mass from the leg.

HISTOPATHOLOGIC DESCRIPTION:  Haired skin:  Expanding the subcutis is a 10 X 15 mm well-circumscribed, unencapsulated, multiloculated neoplasm composed of basaloid polygonal cells which line variably sized cystic structures.  Neoplastic cells are intensely basophilic, often pile on top of each other up to 30 cells deep, have indistinct cell borders, scant amounts of eosinophilic to amphophilic granular cytoplasm, round to oval nuclei, finely stippled chromatin, and indistinct nucleoli.  Mitotic figures average one to two per HPF.  Neoplastic cells exhibit abrupt keratinization, which is characterized by direct transition of basal to keratinized squamous cells, which lack keratohyalin granules and have faded nuclei (ghost cells).  Multifocally, groups of these cells surround concentric rings of a lamellated, eosinophilic keratin.  Multifocally ruptured cysts contain fibroblasts, small caliber blood vessels, foci of brown, granular intracellular and extracellular pigment (melanin), and many scattered plasma cells, melanomacrophages, moderate numbers of multinucleated giant cells (foreign body type) and fewer lymphocytes and neutrophils.

MORPHOLOGIC DIAGNOSIS:  Haired skin:  Pilomatricoma, breed unspecified, canine.

SYNONYMS:  Pilomatrixoma; necrotizing and calcifying epithelioma; epithelioma of Malherbe

SLIDE E
Signalment (JPC #4088229):  Yorkshire terrier

HISTORY:  Mass from left caudal thorax

HISTOPATHOLOGIC DESCRIPTION:  Haired skin:  Expanding the dermis and subcutis,  and compressing the panniculus carnosus is a compression encapsulated, well demarcated, well-circumscribed moderately cellular neoplasm composed of polygonal cells arranged in islands and radiating cords, supported and separated by a moderate fibrovascular stroma, which variably contains lightly basophilic material (mucin).  Neoplastic cells have indistinct cell borders, abundant pale eosinophilic often glassy cytoplasm, irregularly round to oval vesiculate nuclei and contain one often distinct nucleolus.  Mitotic figures average less than one per 10 HPF.  Within the islands of neoplastic cells are multifocal lamellations of brightly eosinophilic keratin (tricholemmal keratinization). Occasionally, nuclei contain a round eosinophilic cytoplasmic invagination, and cells contain intracytoplasmic brown granular material (melanin).

MORPHOLOGIC DIAGNOSIS:  Haired skin:  Tricholemmoma, isthmus type, Yorkshire terrier, canine.

GENERAL DISCUSSION:

PATHOGENESIS:

TYPICAL CLINICAL FINDINGS:

TYPICAL GROSS FINDINGS: 

TYPICAL LIGHT MICROSCOPIC FINDINGS:

ADDITIONAL DIAGNOSTIC TESTS: 

DIFFERENTIAL DIAGNOSIS:

COMPARATIVE PATHOLOGY:

References:

  1. Bogiovanni L, Maltesta D, Brachelente C, D’Equidio S, Della Salda L. β-catenin in canine skin: Immunohistochemical pattern of expression in normal skin and cutaneous epithelial tumours. J Comp Path. 2011; 145(2-3): 138-47.
  2. Brachelente C, Portcellato I, Sforna M, Lepri E, Mechelli L, Bongiovanni L. The contribution of stem cells to epidermal and hair follicle tumours in the dog. Vet Dermatol. 24(1): 188-94.e41.
  3. Carroll EE, Fossey SL, Mangus LM, Carsillo ME, Rush LJ, McLeod CG, Johnson TO. Malignant pilomatricoma in 3 Dogs. Vet Pathol. 2010; 47(5):937-943.
  4. Mauldin EA, Peters-Kennedy J. Integumentary system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 1. 6th ed. St. Louis, MO: Elsevier; 2016: 714-17.
  5. Goldschmidt M, Dunstan R, Stannard A, von Tascharner C, Walder E, Yager J. Histological classification of epithelial and melanocytic tumors of the skin of domestic animals. In: Schulman FY, ed. World Health Organization, International Histological Classification of Tumors of Domestic Animals. Vol 3. 2nd ed. Washington, D.C.: American Registry of Pathology; 1998: 12-13, 21-25, 42-44, 55-62.
  6. Gross TL, Ihrke PF, Walder EJ, Affolter VK. Skin Diseases of the Dog and Cat. 2nd ed. Ames, IA: Blackwell Publishing; 2005: 616-625.
  7. Meuten, D J. Tumors in Domestic Animals. 4th ed. Ames, IA: Iowa State Press; 2002: 55-63.
  8. Miller WH, Griffin CE, Campbell KL. Small Animal Dermatology. 7th ed. St. Louis, MO: Elsevier; 2013:785-8.
  9. Pieper JB, Stern AW, LeClerc SM, Campbell KL. Coordinate expression of cytokeratins 7, 14, and Bcl-2 in canine cutaneous epithelial tumors and cysts. J Vet Diagn Invest. 2015:27(4)
  10. Von Bomhard W, Goldschmidt MH, Shofer FS, Perl L, Rosenthal KL, Mauldin EA. Cutaneous neoplasms in pet rabbits: A retrospective study. Vet Pathol. 2007: 44:579-588.
  11. Welle MM, Wiener DJ. The hair follicle: A comparative review of canine hair follicle anatomy and physiology. Toxicol Pathol. 2016: 44(4):564-74

Tumor

Keratinization

Ghost cells

Histologic features

Origin

IKA

Gradual keratinization

No

Central keratin filled pore

 

Complex cyst wall has mucinous matrix

Infundibulum/ Isthmus

Trichoepithelioma

Gradual & abrupt keratinization

Yes

Can differentiate to all 3 segments of the hair follicle; abortive trichogenesis

Hair matrix cells; inner & outer sheath

Pilomatricoma

Abrupt keratinization

(a small amount of gradual possible as well)

Yes

Basaloid polygonal cells that surround a central zone of ghost cells

 

Pigment

 

Bone and mineral possible

Hair matrix cells; inner sheath

Tricholemmoma

Some central tricholemmal keratinization

No

Abundant pale "glassy" cytoplasm

 

Brightly eosinophilic basement mebrane

Isthmus/ Inferior

Trichoblastoma

No keratinization

No

Variable; undulating ribbons; medusoid

Hair matrix cells

 


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