PMC9720392_01
Macroscopic findings of extragonadal teratoma at 1st-8th caudal vertebrae in a male kitten. (A) A firm, well-circumscribed mass with size ~4.8 x 8.5 x 4.5 cm was located at the ventral part of the caudal vertebrae. (B,C) The cross section of the mass revealed hairs, teeth and multiple cystic structures. (D) The surgical wound after suture removal.
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F1
An 8-month-old, domestic short hair, intact male cat was presented to a private animal hospital with a chief complaint of a slow growing skin mass on the ventral tail between the 1st to 8th coccygeal vertebrae (Figure 1A) observed since the animal was born. The surgical wound healed, and the stitches were removed 10 days after the operation (Figure 1D). The associated multilobulated bulks of adipose tissue, comprising the sac wall (Figures 1B,C), was located at the ventral part of the caudal vertebrae.
Microscopic findings of ectodermal components. (A) The neuronal tissue was composed of many glial cells amid fibrillar to neuropil. H&E. Bar = 50 mum. (B) Glial cells showed immunostaining with GFAP (white arrows). IHC. Bar = 50 mum. (C) Neurons showed immunostaining with Neuron-n (white arrow). IHC. Bar = 50 mum. (D) Area of tissue differentiation toward tooth characterized by large island of eosinophilic dentin and enamel with palisading layer of ameloblasts amid variably dense periodontal ligament stroma. H&E. Bar = 50 mum.
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F2
For the ectoderm, there were areas of eosinophilic granular and fibrillar neuropil along with neural parenchyma of respective gray and white matter containing variable numbers of glial cells and neurons (Figure 2A), often intermingled with portions of mesenchymal tissue such as smooth muscle fibers or preexisting dermal collagen stroma. In the section through the teeth and associated alveolar bone, there was a large island of amphophilic dentin rimmed by ~50-70 mum thick, hyalinized, eosinophilic bands of enamel with an associated single palisading layer of tall columnar ameloblasts and variably loosely edematous periodontal ligament (Figure 2D). In regions of neural tissue, several glial cells were immunoreactive for GFAP (Figure 2B). Some neurons are stained with neuron-n (Figure 2C).
Microscopic findings of mesodermal components. (A,B) The mesodermal tissue consisted of cartilages, adipocytes, smooth muscles and bony trabeculae. H&E. Bar = 100 mum. (C) The proximal margin contained pools of hematopoietic cells. H&E. Bar = 50 mum. (D) Smooth muscles were highlighted with alpha smooth muscle actin. IHC. Bar = 100 mum.
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F3
For the mesoderm, there were small, isolated lobules of well differentiated cartilage (Figure 3A), irregular trabeculae of bone (Figure 3B), often associated with marrow hematopoietic precursors (Figure 3C), bands of smooth muscle and myocardial fibers, and adipose tissue. Smooth muscle fibers revealed strong cytoplasmic immunoreactivity for SMA (Figure 3D).