JPC SYSTEMIC PATHOLOGY

INTEGUMENTARY SYSTEM

September 2016

I-N02

 

Signalment (JPC # 1754646):  Guinea pig

HISTORY:  Dermal mass

HISTOPATHOLOGIC DESCRIPTION:  Haired skin:  Expanding the dermis and subcutis, compressing the adjacent adnexa and panniculus carnosus, and elevating the overlying epidermis is a 2 x 1.5 cm, unencapsulated, well circumscribed, cystic, multilobulated, neoplasm composed of polygonal cells arranged in numerous arborizing primitive folliculosebaceous units around a central cyst (primary follicle) on a moderate fibrovascular stroma.  Neoplastic cells have indistinct borders and contain a scant to moderate amount of eosinophilic cytoplasm with a round to oval nucleus containing finely stippled chromatin and one to two indistinct nucleoli.  Mitoses average 2 per HPF.  The primary follicle is lined by attenuated epithelium that undergoes both abrupt and gradual keratinization.  The arborizing folliculosebaceous units are composed of secondary follicles that undergo varying degrees of differentiation and incompletely recapitulate hair follicles.  The secondary follicles are characterized by a peripheral layer of basaloid cells that mature to attenuated squamous cells centrally or form hair bulbs and occasionally birefringent hair shafts.  The central squamous cells often contain eosinophilic, 2‑4 um, irregularly shaped, brightly eosinophilic granules (trichohyalin granules).  Multifocally there is sebaceous differentiation.   

MORPHOLOGIC DIAGNOSIS:  Haired skin:  Trichofolliculoma, guinea pig, rodent.

GENERAL DISCUSSION:

PATHOGENESIS:

TYPICAL GROSS FINDINGS:

TYPICAL LIGHT MICROSCOPIC FINDINGS:

DIFFERENTIAL DIAGNOSIS:

COMPARATIVE PATHOLOGY:

REFERENCES:

  1. Gross TL, Ihrke PF, Walder EJ, Affolter VK. Skin Diseases of the Dog and Cat. 2nd ed. Ames, IA: Blackwell Publishing; 2005: 616-625.
  2. 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: Saunders; 2016:705.
  3. Mohr U. International Classification of Rodent Tumors Part I-The Rat: 5. Integumentary System. International Agency for Research on Cancer, Lyon, France, 1993:1.
  4. Murphy GF, Elder DE. Non-melanocytic tumors of the skin.  In: Rosal J, Sobin LH, eds. Atlas of Tumor Pathology. 3rd Series.  Fascicle 1. Washington, DC:Armed Forces Institute of Pathology; 1990: 138-139.
  5. O’Rourke DP. Disease problems of guinea pigs. In: Quesenberry KE, Carpenter JW, eds.  Ferrets, Rabbits, and Rodents Clinical Medicine and Surgery. 2nd ed. St. Louis, MO:Saunders; 2004:251.
  6. Percy DH, Barthold SW. Pathology of Laboratory Rodents and Rabbits. 4th ed. Ames, IA:Blackwell Publishing; 2016:250.
  7. Sharov AA, Mardaryev AN, Sharova TY, Grachtchouk M, Atoyan R, Byers HR, Seykora JT, Overbeek P,  Dlugosz A, Botchkare VA. Bone morphogenetic protein antagonist noggin promotes skin tumorigenesis via stimulation of the Wnt and Shh signaling pathways. Am J Path. 2009:175(3).


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