Page 69 - Differential Diagnosis in Small Animal Cytology, The Skin and Subcutis

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• Infundibular cyst
Usually exfoliates numerous anucleated squamous epithelial cells. These are intact and
VetBooks.ir with well defined margins. They vary from being lightly to moderately basophilic.
Occasionally, they may be embedded in a watery basophilic background of keratinic
material.
• Isthmic cyst
Aspirates usually contain pale, amorphous and homogeneous keratin.
• Matrical cyst
Characterized by the exfoliation of variable numbers of ghost cells (description of
ghost cells can be found in the pilomatricoma section in Chapter 8).
• Hybrid cyst
This type of cyst contains a mixture of the anucleated squames and keratinized material
typical of the other cysts described above.

Differential diagnoses
• Infundibular keratinizing acanthoma (no ghost cells seen)
• Trichoepithelioma
• Pilomatricoma

(A) (B)

(C) (D)

Fig. 7.1. Dog. Variants of follicular cyst. (A) Polygonal anucleated squamous epithelial cells suggestive of an
infundibular cyst. (B) Liquid keratin with low numbers of lamellar anucleated squamous epithelial cells suggestive of
an infundibular cyst. Cholesterol crystals are also observed. (C) Dense and homogeneous keratin suggestive of an
isthmic cyst. (D) Ghost cells suggestive of a matrical cyst. Wright-Giemsa.