Tropical Medicine: A Clinical Text, 8th Edition, Revised and Expanded

Miscellaneous

Miscellaneous Tropical Tumors Several important malignant tumors occur in tropical settings. These include the following. Burkitt’s Lymphoma In the late 1950s, Dennis Burkitt, an Irish surgeon working in Uganda with O’Connor and Davies, described an endemic form of B cell lymphoma affecting the jaws of children. It is now recognized as the most common childhood cancer in subequatorial Africa and in Papua New Guinea; rare cases have been reported from countries around the world. Pathology Burkitt’s lymphoma is found primarily in the bones of the jaw and in the ovaries of young girls. Undifferentiated lymphoblasts surround scattered large clear histiocytes, giving a ‘‘starry sky’’ appearance under low-power microscopy. The tumors are commonly multiple, symmetrical, and extremely fast growing, with a cell doubling time of only 24 hours. They reach an enormous size within a matter of days. These tumors also occur in the kidneys, retroperitoneal tissues, thyroid, distal long bones, breast, testes, and parotid glands. The pathogenesis of Burkitt’s lymphoma is not altogether clear, but it involves a complex relationship among Chronic P. falciparum infection Persistent Epstein-Barr virus (EBV) infection Chromosomal translocations in B lymphocytes with deregulation of the oncogenic c  myc gene PAGE 240 ................. 18086$ CH20 07-15-11 13:51:00 PS miscellaneous 241 Clinical Features The most common presentation is a young child with a unilateral or bilateral facial swelling. Some children are first seen by a dentist because of loosening of deciduous molar teeth. A maxillary tumor may obliterate the antrum, and the palate bulges downward. The tumor may also spread upward into the orbit, causing proptosis and destruction of the eye. Pain is seldom severe, and the cervical lymph nodes are not involved. X-ray of the jaw reveals osteolytic lesions with erosion round the roots of the teeth. In northern Nigeria, large ovarian tumors develop in girls ages 10 to 16. A less-common presenting symptom is a flaccid paraplegia due to extension of a retroperitoneal tumor. Diagnosis and Treatment The diagnosis is confirmed either by biopsy or aspiration of tumor material. In view of the rapid growth of these tumors, treatment is urgent, and 80% to 90% of these patients will respond initially to aggressive cytotoxic therapy. Large abdominal tumors should be removed surgically. Despite periods of remission, relapses occur in 60% of cases. Relapses within 3 months seldom respond to further chemotherapy , but those occurring after this period respond well. A 70% cure rate may be expected in African children with only jaw involvement. Important complications of cytotoxic drug treatment are hyperkalemia and hyperuricemia with acute renal failure. Nasopharyngeal Carcinoma Nasopharyngeal carcinoma is more than 10 to 20 times as common in southern Chinese as in Europeans. As with Burkitt’s lymphoma, this tumor appears to be associated with EBV infection. EBV can be detected in tumor cells, and serological titers for EBV antibodies are directly proportional to the amount of tumor present. The clinical presentation is varied and often confusing. Common manifestations include obstruction of the Eustachian or nasal passages, cervical lymphadenopathy , persistent neuralgic facial pain, cranial nerve palsies, and proptosis due to orbital involvement. The small primary lesion in the post-nasal space is frequently not recognized until later complications PAGE 241 ................. 18086$ CH20 07-15-11 13:51:01 PS 242 miscellaneous emerge. Radiotherapy is often successful, but patients with cranial nerve palsies or cervical lymph node involvement have a poor prognosis. Kaposi’s Sarcoma Yet another tumor, which may or may not be secondary to a viral infection , is the endemic Kaposi’s sarcoma of central Africa and Papua New Guinea, where it accounts for 9% of recorded malignancies. The ‘‘epicenter ’’ of endemicity in Africa is in eastern Zaire. Kaposi’s sarcoma is also a major complication of HIV/AIDS. Pathology In African men, Kaposi’s sarcoma is a very slowly progressive disease of the extremities, characterized by purple nodules and local edema. Early in the course of the disease, the histologic picture consists of dilated, thin-walled vascular spaces with jagged outlines, sparsely infiltrated with lymphocytes and plasma cells. Later, there is spindle cell proliferation with frequent mitosis. The steady growth of these lesions, the limited geographical distribution, and the association with immunode ficiency have suggested a viral origin. Clinical Features There are two peaks of incidence: the first in children of either sex, ages 2 to 3 years; and the second in adult men. In children...