Miscellaneous Pathology

·         Clear vacuolization of the superficial layers of the epithelial cells (koilocytosis) is characteristic of infection by human papillomavirus (HPV). These changes are found in both condyloma acuminatum and verrucous carcinoma, but condyloma is a benign papillary lesion that does not grow into the underlying tissue, while verrucous carcinoma, also known as giant condyloma or Buschke-Löwenstein tumor, invades the underlying tissue.

·         Acute endometritis is usually caused by bacterial infection following delivery or miscarriage and is characterized by the presence of neutrophils in endometrial tissue that is not menstrual endometrium. The histologic diagnosis of chronic endometritis depends on finding plasma cells within the endometrium.

·         These fibrocystic changes are subdivided into nonproliferative and proliferative changes. Nonproliferative changes include fibrosis of the stroma and cystic dilation of the terminal ducts, which when large may form blue-domed cysts. A common feature of the ducts in nonproliferative changes is apocrine metaplasia, which refers to epithelial cells with abundant eosinophilic cytoplasm with apical snouts.

Proliferative changes include epithelial hyperplasia of the ducts. This hyperplastic epithelium may form papillary structures (papillomatosis when pronounced), or may be quite abnormal (atypical hyperplasia). Two benign, but clinically important, forms of proliferative fibrocystic change include sclerosing adenosis and radial scar. Both of these may be mistaken histologically for infiltrating ductal carcinoma, but the presence of myoepithelial cells is a helpful sign that points to the benign nature of the proliferation. Sclerosing adenosis is a disease of the terminal lobules that is typically seen in patients 35 to 45 years old. It produces a firm mass, most often located in the upper outer quadrant. Microscopically there is florid proliferation of small ductal structures in a fibrous stroma, which on low power is stellate in appearance and somewhat maintains the normal lobular architecture. A radial scar refers to ductal proliferation around a central fibrotic area.

·         Gynecomastia (enlargement of the male breast) histologically reveals epithelial hyperplasia within the ducts that is surrounded by hyalinized fibrous tissue.

·         A MIXED LYMPHOCYTE REACTION ASSAYS the histocompatibility between two individuals. Donor cells are treated to prevent DNA synthesis and proliferation. The recipient's cells are mixed with the donor's cells. If the donor's cells express foreign MHC antigens, the recipient's lymphocytes will proliferate. Proliferation can be measured by the uptake of radioactive thymidine.

·         Two infections classically associated with pseudomembrane formation are Clostridium difficile, which produces a characteristic “mushroom-shaped” pseudomembrane in the colon of people taking broad-spectrum antibiotics, and C. diphtheriae, which produces a pseudomembrane in the larynx.