Soft Tissue Nonneoplastic Masses






Hypertrophic scar



Nevi and Hamartoma

A hamartoma is a proliferation of mature tissue in a location where it is normally found. Hamartomas are found in the very young and in older animals. In humans, some hamartomas are known to arise because of loss of function of genes that limit the mTOR (mechanistic target of rapomycin) pathway and activity particulary in Tuberus Sclerosis Complex.

Cutaneous horn

Linear organoid nevus


There is a case report about a dog with a linear mass composed of sebaceous glands.

Warty dyskeratoma

Seborrhiec keratoma

Sebaceous nodular hyperplasia



Pilar neurocristic hamartoma

This hamartoma derives its name from a hair follicle (pilar) and mesenchymal cells of the neural crest, usually with spindle cells, Schwann cells, pigmented dendritic cells and or melanocytes.They are often pigmented in appearance. They are multifocal/multinodular.


Anderson WI, Luther PB, Scott DW. Pilar neurocristic melanoma in four dogs. Vet Rec. 1988; 123: 517-518.

Smooth Muscle Hamartoma

Well demarcated and expansile nodules of smooth muscle that form a mass in the dermis is a smooth muscle hamartoma. These are derived from the arrector (erector) pili muscle.


Liu SM, Mikaelian I. Cutaneous Smooth Muscle Tumors in the Dog and Cat. Vet Pathol 2003; 40: 685–692