Malignant Tumors: Histology, Metastases

Malignant Tumors: Histology, Metastases

Carcinoma of the pancreas varies a great deal on pathologic examination. It may be a small, localized tumor com­pletely obstructing the common bile and pancreatic ducts, or it may be a large, pale-white, hard tumor mass, filling much of the head  of the pan­creas but still remaining well localized. When discovered, those in the body and tail are usually extensive, with peritoneal involvement and extension to other sites. Because of the close contact with the duodenum and the lymphatic connection (see page 30), invasion of the duodenum with large tumors is so common that it may be impossible to determine which was the primary site. Extension via the perineural lymphatics occurs early and may partially explain the early appear­ance of pain in carcinoma of the pan­creas. The extensive lymphatic drainage and its quick involvement by the cancer explains, at least in part, the difficulty in obtaining cure by feasible extent of resection. Extension beyond the peripan – creatic lymphatics involves the regional nodes along the common duct, the peri­aortic nodes, the liver and, via the gastric nodes, the mediastinum and neck. Direct spread, also takes place to the stomach, colon, spleen and kidney, and ero­sion through the surface of the gland and overlying peritoneum permits seed­ing of either the lesser or general peri­toneal cavities. The pancreatic ducts are the most frequent site of origin of the cancer, which explains the increased occurrence of the disease in the head and the frequent obstruction of the main duct even by small tumors.

Malignant Tumors Histology

Malignant Tumors: Histology

Microscopically, the pancreatic malignant tumors are primarily adenocarci­nomas of several types. Epidermoid carcinoma does occur as a primary tumor in the pancreas, but it is rare. Medullary carcinoma grows in solid sheets and banks of cells, arranged in a haphazard manner but rather uniform in size, shape and staining quality. In some areas they form ill-defined acini. The well-differ – entiated duct cell carcinoma grows as irregular ductlike or glandular structures formed by one or more layers of cuboidal or columnar cells, separated by abundant fibrous tis­sue. At times, these may be difficult to distinguish from chronic pancreatitis. Anaplastic carcinoma, as is characteristic of this type in other organs, is made up of irregular masses of cells which vary considerably in size, shape and staining quali­ties. The nuclei are usually hyperchromatic, with large nucleoli and frequent mitoses. The cytoplasm is abundant, eosinophilic and, in some cases, vacuolated.

Metastases from carcinoma of the pancreas to distant organs other than by lymphatic spread are, in order of frequency, the liver, lungs, intestine, adrenal, bone, diaphragm, gallbladder, kidney, heart, medias­tinum, bladder, ovary and muscle, skin or subcu­taneous tissue.

Malignant Tumors: Metastases

Malignant Tumors: Metastases

Metastatic carcinoma to the pancreas from other organs has received little attention. It does occur with some frequency and, at times, may cause difficulty in differential diagnosis between primary and metastatic cancer. The lung is the most common source of primary carcinoma, and here we have a particu­larly difficult differential diagnosis, because anaplastic carcinoma is found in both organs. Metastatic mela­noma is next in frequency, then breast, kidney, thy­roid, ovary, uterus, prostate and, perhaps, parotid gland carcinoma. Metastatic sarcoma is also encountered.

The pancreas is frequently invaded by direct exten­sion of a carcinoma in the stomach, kidney, colon, duodenum, the papilla of Vater and the common bile duct, in which case the original tumor may actuall) arise in an intrapancreatic position. Lymphatic tumors such as Hodgkin’s disease or lymphoma, involving the regional lymph nodes, may also extend directly into the pancreas. These instances of direct extensior can be easily. understood from the topographic rela tions of the organ.

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