Tertiary dentin (including reparative dentin or sclerotic dentin) – pathologic
Tertiary dentin is dentin formed as a reaction to external stimulation such as cavities and wear. It is of two types, either reactionary, where dentin is formed from a pre-existing odontoblast, or reparative, where newly differentiated odontoblast-like cells are formed due to the death of the original odontoblasts, from a pulpal progenitor cell. Tertiary dentin is only formed by an odontoblast directly affected by a stimulus; therefore, the architecture and structure depend on the intensity and duration of the stimulus, e.g., if the stimulus is a carious lesion, there is extensive destruction of dentin and damage to the pulp, due to the differentiation of bacterial metabolites and toxins. Thus, tertiary dentin is deposited rapidly, with a sparse and irregular tubular pattern and some cellular inclusions; in this case, it is referred to as "osteodentin". Osteodentin is seen in Vit.A deficiency during development. However, if the stimulus is less active, it is laid down less rapidly with a more regular tubular pattern and hardly any cellular inclusions. The speed at which tertiary dentin forms also varies substantially among primate species. Animal dentin
Elephant ivory is solid dentin. The structure of the dentinal tubules contributes to both its porosity  and its elasticity. Elephant tusks are formed with a thin cap of enamel, which soon wears away, leaving the dentin exposed. Exposed dentin in humans causes the symptom of sensitive teeth.
High-grade prostatic intraepithelial neoplasia (HGPIN) is an abnormality of prostatic glands and believed to precede the development of prostate adenocarcinoma (the most common form of prostate cancer).It may be referred to simply as prostatic intraepithelial neoplasia (PIN). It is considered to be a pre-malignancy, or carcinoma in situ, of the prostatic glands. Signs and symptoms
HGPIN in isolation is asymptomatic. It is typically discovered in prostate biopsies taken to rule-out prostate cancer and very frequently seen in prostates removed for prostate cancer. Relation to prostate cancer
There are several reasons why PIN is the most likely prostate cancer precursor. PIN is more common in men with prostate cancer. High grade PIN can be found in 85 to 100% of radical prostatectomy specimens, nearby or even in connection with prostate cancer. It tends to occur in the peripheral zone of the prostate. With age, it becomes increasingly multifocal, like prostate cancer. Molecular analysis has shown that high grade PIN and prostate cancer share many genetic abnormalities.The risk for men with high grade PIN of being diagnosed with prostate cancer after repeat biopsy has decreased since the introduction of biopsies at more than six locations (traditional sextant biopsies). Histology
HGPIN typically has one of four different histologic patterns:
tufted,
micropapillary,
cribriform and,
flat.Its cytologic features are that of prostatic adenocarcinoma:

presence of nucleoli,
increased nuclear-to-cytoplasmic ratio and,
increased nuclear size.Microscopically, PIN is a collection of irregular, atypical epithelial cells. The architecture of the glands and ducts remains normal. The epithelial cells proliferate and crowding results in a pseudo-multilayer appearance.