JPC Systemic Pathology

Integumentary System

September 2016



Signalment (JPC Accession #2634082):  Age and breed unspecified, dog

HISTORY:  This dog had a solitary, slow-growing dermal mass on the head.

HISTOPATHOLOGIC DESCRIPTION:  Haired skin, head:  Focally expanding the dermis and subcutis, elevating the overlying epidermis and compressing adjacent adnexa is a 12mm diameter, densely cellular, unencapsulated, well-demarcated, well-circumscribed, multilobulated neoplasm composed of polygonal basaloid cells arranged in variably-sized cords, trabeculae, undulating ribbons, garlands and occasional islands.  The cords and trabeculae are separated and surrounded by a dense, often hyalinized collagenous stroma, whereas the ribbons and garlands are separated by moderately dense fibrous to myxomatous stroma.  Neoplastic cells have variably distinct cell borders, scant eosinophilic cytoplasm, oval nucleus with finely stippled chromatin, and one variably indistinct nucleolus.  Multifocal islands of neoplastic cells have more abundant, finely granular eosinophilic cytoplasm.  Neoplastic cells occasionally line small (up to 80um) cystic structures containing flocculent amphophilic material.  The mitotic rate averages 2 per 10 HPF.  Anisocytosis and anisokaryosis are minimal.

MORPHOLOGIC DIAGNOSIS:  Haired skin, head:  Trichoblastoma, breed not specified, canine

Signalment (JPC Accession #2015906):  Age and breed unspecified, cat

HISTORY:  Cystic mass from the neck

HISTOPATHOLOGIC DESCRIPTION:  Dermis, neck:  Expanding the dermis, replacing adnexal structures, and extending to all borders is a densely cellular, well-demarcated, multilobular, unencapsulated neoplasm composed of two morphologies of polygonal cells arranged in variably sized islands and cords which often form thick-walled cysts, and are separated by a moderately dense fibrous stroma.  The first polygonal to vaguely spindloid cell population has indistinct cell borders, a scant amount of eosinophilic cytoplasm, and a single elongate nucleus with dense chromatin and an indistinct nucleolus.  Anisocytosis and anisokaryosis are mild.  These cells often contain intracytoplasmic black granules (melanin).  The second more polygonal population is arranged in islands within the trabeculae and has distinct cell borders, a moderate amount of eosinophilic cytoplasm with a single round nucleus with finely stippled chromatin and a distinct nucleolus.  Anisocytosis and anisokaryosis are mild.  The mitotic count for both cell morphologies averages 6 per 10HPF.  The center of the cysts often contains abundant necrotic neoplastic cells and melanin pigment. 

MORPHOLOGIC DIAGNOSIS:  Dermis, neck:  Solid-cystic and pigmented apocrine ductular adenoma, breed not specified, feline.




Solid-cystic apocrine ductular adenomas:




Solid-cystic apocrine ductular adenomas – cats:


Trichoblastoma – histological subtype does not affect prognosis; usually not contiguous with epidermis

Solid-cystic apocrine ductular adenoma - cats



For trabecular trichoblastoma:

For granular trichoblastoma:

For spindle cell trichoblastoma:

For trichoblastoma with ORS differentiation (dogs):

For solid-cystic apocrine ductular adenoma (cats):



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  3. Goldschmidt MH, Dunstan RW, Stannard AA, von Tscharner C, Walder EJ, Yager J. Histological Classification of Epithelial and Melanocytic Tumors of the Skin of Domestic Animals. 2nd Series, Vol. III. Washington, DC: Armed Forces Institute of Pathology; 1998: 18-19, 22-23.
  4. Gross TL, Ihrke PJ, Walder EJ: Epithelial neoplasms and other tumors. In: Gross TL, ed. Skin Diseases of the Dog and Cat. 2nd ed. Ames, IA: Blackwell Science; 2005: 625-634, 672-677.
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  6. 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: 714-716, 718-719.
  7. Schaffer PA, Wobeser B, Martin LER, Dennis MM, Duncan CG. Cutaneous neoplastic lesions of equids in the central United States and Canada: 3,351 biopsy specimens from 3,272 equids (2000-2010). J Am Vet Med Assoc. 2013;242(1):99-104.
  8. 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(5):579-588.

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